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Cognitive Psychology and Cognitive Neuroscience/Evolutionary Perspective on Social Cognitions

Introduction
Why do we live in cities? Why do we often choose to work together? Why do we enjoy sharing our spare time with others? These are questions of Social Cognition and its evolutionary development.

The term Social Cognition describes all abilities necessary to act adequately in a social system. Basically, it is the study of how we process social information, especially its storage, retrieval and application to social situations. Social Cognition is a common skill among various species.

In the following, the focus will be on Social Cognition as a human skill. Important concepts and the development during childhood will be explained. Having built up a conceptional basis for the term, we will then take a look at this skill from an evolutionary perspective and present the common theories on the origin of Social Cognition.

The publication of Michael Tomasello et al. in the journal Behavioral and Brain Sciences (2005) will serve as a basis for this chapter.

The human faculty of Social Cognition
Humans are by far the most talented species in reading the minds of others. That means we are able to successfully predict what other humans perceive, intend, believe, know or desire. Among these abilities, understanding the intention of others is crucial. It allows us to resolve possible ambiguities of physical actions. For example, if you were to see someone breaking a car window, you would probably assume he was trying to steal a stranger's car. He would need to be judged differently if he had lost his car keys and it was his own car that he was trying to break into. Humans also collaborate and interact culturally. We perform complex collaborative activities, like building a house together or playing football as a team. Over time this led to powerful concepts of organizational levels like societies and states. The reason for this intense development can be traced back to the concept of Shared Intentionality.

Shared Intentionality
An intentional action is an organism's intelligent behavioural interaction with its environment towards a certain goal state. This is the concept of Problem Solving, which was already described in the previous chapter.

The social interaction of agents in an environment which understand each other as acting intentionally causes the emergence of Shared Intentionality. This means that the agents work together towards a shared goal in collaborative interaction. They do that in coordinated action roles and mutual knowledge about themselves. The nature of the activity or its complexity is not important, as long as the action is carried out in the described fashion. It is important to mention that the notion of shared goals means that the internal goals of each agent include the intentions of the others. This can easily be misinterpreted. For example, take a group of apes on a hunt. They appear to be acting in a collaborative way, however, it is reasonable to assume that they do not have coordinated action roles or a shared goal – they could just be acting towards the same individual goal. Summing up, the important characteristics of the behaviour in question are that the agents are mutually responsive, have the goal of achieving something together and coordinate their actions with distributed roles and action plans.

The strictly human faculty to participate in collaborative actions that involve shared goals and socially coordinated action plans is also called Joint Intention. This requires an understanding of the goals and perceptions of other involved agents, as well as sharing and communicating these, which again seems to be a strictly human behaviour. Due to our special motivation to share psychological states, we also need certain complex cognitive representations. These representations are called dialogic cognitive representations, because they have as content mostly social engagement. This is especially important for the concept of joint intentions, since we need not only a representation for our own action plan, but also for our partner's plan. Joint Intentions are an essential part of Shared Intentionality.

Dialogic cognitive representations are closely related with the communication and use of linguistic symbols. They allow in some sense a form of collective intentionality, which is important to construct social norms, conceptualize beliefs and, most importantly, share them. In complex social groups the repeated sharing of intentions in a particular interactive context leads to the creation of habitual social practices and beliefs. That may form normative or structural aspects of a society, like government, money, marriage, etc. Society might hence be seen as a product and an indicator of Social Cognition.

The social interaction that builds ground for activities involving Shared Intentionality is proposed to be divided into three groups:

 * Dyadic engagement: The simple sharing of emotions and behaviour, by means of interaction and direct mutual response between agents. Dyadic interaction between human infants and adults are called protoconversations. These are turn-taking sequences of touching, face expressions and vocalisations. The exchange of emotions is the most important outcome of this interaction.

 * Triadic engagement: Two agents act together towards a shared goal, while monitoring the perception and goal-direction of the other agent. They focus on the same problem and coordinate their actions respectively, which makes it possible to predict following events.

 * Collaborative engagement: The combination of Joint Intentions and attention. At this point, the agents share a goal and act in complementary roles with a complex action plan and mutual knowledge about the selective attention and the intentions of one another. The latter aspect allows the agents to assist each other and reverse or take over roles.

These different levels of social engagement require the understanding of different aspects of intentional action, as introduced above, and presuppose the motivation to share psychological states with each other.

Development of Social Cognition during childhood
A crucial point for Social Cognition is the comprehension of intentional action. Children's understanding of intentional action can basically be divided into three groups, each representing a more complex level of grasp.
 * 1) The first one to be mentioned is the identification of animate action. This means that after a couple of months, babies can differentiate between motion that was caused by some external influence and actions that an organism has performed by itself, as an animate being. At this stage, however, the child has not yet any understanding of potential goals the observed actor might have, so it is still incapable of predicting the behaviour of others.
 * 2) The next stage of comprehension includes the understanding that the organism acts with persistence towards achieving a goal. Children can now distinguish accidental incidents from intentional actions and failed from successful attempts. This ability develops after about 9 months. With this new perspective, the child also learns that the person it observes has a certain perception - thus a certain amount of predicting behaviour is possible. This is an essential difference between the first and the second stage.
 * 3) After around 14 months of age, children fully comprehend intentional action and the basics of rational decision making. They realise, that an actor pursuing a goal may have a variety of action plans to achieve a goal, and is choosing between them. Furthermore, a certain sense for the selective attention of an agent develops. This allows a broad variety of predictions of behaviour in a certain environment. In addition to that, children acquire the skill of cultural learning: when they observe how an individual successfully reaches a goal, they memorise the procedure. Hence, they can use the methods to reach their own goals. This is called imitative learning, which turns out to be an extremely powerful tool. By applying this technique, children also learn how things are conventionally done in their culture.

Evolutionary perspective on Social Cognition
So far we discussed what Social Cognition is about. But how could this behaviour develop during evolution? At first glance, Darwin’s theory of the survival of the fittest does not support the development of social behaviour. Caring for others, and not just for oneself, seems to be a decrease of fitness. Nevertheless, various theories have been formulated which try to explain Social Cognition from an evolutionary perspective. We will present three influential theories which have been formulated by Steven Gaulin and Donald McBurney.

Group Selection
Vero Wynne-Edwards first proposed this theory in the 1960s. From an evolutionary perspective, a group is a number of individuals which affect the fitness of each other. Group Selection means that if any of the individuals of a group is doing benefit to its group, the group is more likely to survive and pass on its predisposition to the next generation. This again improves the chance of the individual to spread its genetic material. So in this theory a social organism is more likely to spread its genes than a selfish organism. The distinction to the classical theory of evolution is that not only the fittest individuals are likely to survive, but also the fittest groups.

An example would be the history of the Rapa Nui. The Rapa Nui were the natives of Easter Island which handled their resources extremely wasteful in order to build giant heads made of stone. After a while, every tree on the island was extinct because they needed the trunks to transport the stones. The following lack of food led to the breakdown of their civilization.

A society which handles their resources more moderate and provident would not have ended up in such a fate. However, if both societies would have lived on one island, the second group would not have been able to survive because they would not have been able to keep the resources.

This indicates the problem of the Group Selection: it needs certain circumstances to describe things properly. Additionally, every theory about groups should include the phenomenon of migration. So in this simple form, the theory is not capable of handling selfish behaviour of some agents in altruistic groups: Altruistic groups which include selfish members would turn into pure selfish ones over time, because altruistic agents would work for selfish agents, thereby increasing the cheaters' fitness while decreasing their own. Thus, Group Selection may not be a sufficient explanation for the development of Social Cognition.

Kin Selection
Since altruistic populations are vulnerable to cheaters, there must exist a mechanism that allows altruism to be maintained by natural selection. The Kin Selection approach provides an explanation how altruistic genes can spread without being eliminated by selfish behaviour. The theory was developed by William D. Hamilton and John M. Smith in 1964. The basic principle of Kin Selection is to benefit somebody who is genetically related, for example by sharing food. For the altruistic individual, this means a reduction of its own fitness by increasing the fitness of its relative. However, the closer the recipient is related to the altruist, the more likely he shares the altruistic genes. The loss of fitness can be compensated since the genes of the altruistically behaving agent have then the chance to be spread indirectly through the recipient: The relative might be able to reproduce and pass the altruistic genes over to the next generation.

In principle, the disadvantage for the giver should always be less than the increased fitness of the addressee. This relation between costs and benefit is expressed by Hamilton's rule taking additionally the relatedness of altruist and recipient into account:

$$r \cdot b > c$$ where

 * r shows the genetic relatedness between altruist and recipient (coefficient between zero and one),

 * b is the reproductive benefit or increased fitness for the recipient and

 * c are the altruist's reproductive costs or the reduction of his fitness in the performed action.

If the product of relatedness and benefit outweighs the costs for the giver, the altruistic action should be performed. The closer the recipient is genetically related, the higher costs are acceptable.

Examples for kin-selected altruism can be found in populations of social insects like ants, termites or bees. An ant colony, for instance, consists of one fertile queen and several hundreds or more of sterile female workers. While the queen is the only one reproducing, the workers are among other things responsible for brood care. The workers are genetically closer related to the sisters they raise (75%) than they would be to their own offspring (50%). Therefore, they are passing on more of their genes than if they bred on their own.

According to Hamilton's rule, altruism is only favoured if directed towards relatives, that is $$r > 0$$. Therefore, Kin Selection theory accounts only for genetic relatives. Altruism however occurs among not related individuals as well. This issue is addressed by the theory of Reciprocal Altruism.

Reciprocal Altruism
The theory of Reciprocal Altruism describes beneficial behaviour in expectation of future reciprocity. This form of altruism is not a selfless concern for the welfare of others but it denotes mutual cooperation of repeatedly interacting species in order to maximise their individual utility. In social life an individual can benefit from mutual cooperation, but each one can also do even better by exploiting the cooperative efforts of others. Game Theory allows a formalisation of the strategic possibilities in such situations. It can be shown, that altruistic behaviour can be more successful (in terms of utility) than purely self-interested strategies and therefore will lead to better fitness and survivability.

In many cases social interactions can be modelled by the Prisoner's Dilemma, which provides the basis of our analysis. The classical prisoner's dilemma is as follows: Knut and his friend are arrested by the police. The police has insufficient evidence for a conviction, and, having separated both prisoners, visits each of them to offer the same deal: if one testifies for the prosecution against the other and the other remains silent, the betrayer goes free and the silent accomplice receives the full ten-year sentence. If both stay silent, the police can sentence both prisoners to only six months in jail for a minor charge. If each betrays the other, each will receive a two-year sentence.

Each prisoner has two strategies to choose from, to remain silent (cooperate) or to testify (defect). Assume Knut wants to minimize his individual durance. If Knut's friend cooperates, it is better to defect and go free than to cooperate and spend six months in jail. If Knut's friend defects, then Knut should defect too, because two years in jail are better than ten. The same holds for the other prisoner. So defection is the dominant strategy in the prisoner's dilemma, even though both would do better, if they cooperated. In a one-shot game a rational player would always defect, but what happens if the game is played repeatedly?

One of the most effective strategies in the iterated prisoner's dilemma is the mixed strategy called Tit for Tat: Always cooperate in the first game, then do whatever your opponent did in the previous game. Playing Tit for Tat means to maintain cooperation as long as the opponent does. If the opponent defects he gets punished in succeeding games by defecting likewise until cooperation is restored. With this strategy rational players can sustain the cooperative outcome at least for indefinitely long games (like life). Clearly Tit for Tat is only expected to evolve in the presence of a mechanism to identify and punish cheaters.

Assuming species are not able to choose between different strategies, but rather that their strategical behaviour is hard-wired, we can finally come back to the evolutionary perspective. In The Evolution of Cooperation Robert Axelrod formalised Darwin's emphasis on individual advantage in terms of game theory. Based on the concept of an evolutionary stable strategy in the context of the prisoner's dilemma game he showed how cooperation can get started in an asocial world and can resist invasion once fully established.

Conclusion
Summing up, Social Cognition is a very complex skill and can be seen as the fundament of our current society. On account of the concept of Shared Intentionality, humans show by far the most sophisticated form of social cooperation. Although it may not seem obvious, Social Cognition can actually be compatible with the theory of evolution and various reasonable approaches can be formulated. These theories are all based on a rather selfish drive to pass on our genetic material - so it may be questionable, if deep-rooted altruism and completely selfless behaviour truly exists.


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Digital Signal Processing/Sampling and Reconstruction

digital pro{sampling}
Sampling is the process of recording the values of a signal at given points in time. For A/D converters, these points in time are equidistant. The number of samples taken during one second is called the sample rate. Keep in mind that these samples are still analogue values. The mathematic description of the ideal sampling is the multiplication of the signal with a sequence of direct pulses. In real A/D converters the sampling is carried out by a sample-and-hold buffer. The sample-and-hold buffer splits the sample period in a sample time and a hold time. In case of a voltage being sampled, a capacitor is switched to the input line during the sample time. During the hold time it is detached from the line and keeps its voltage.

Quantization
Quantization is the process of representing the analog voltage from the sample-and-hold circuit by a fixed number of bits. The input analog voltage (or current) is compared to a set of pre-defined voltage (or current) levels. Each of the levels is represented by a unique binary number, and the binary number that corresponds to the level that is closest to the analog voltage is chosen to represent that sample. This process rounds the analog voltage to the nearest level, which means that the digital representation is an approximation to the analog voltage. There are a few methods for quantizing samples. The most commonly used ones are the dual slope method and the successive approximation.

Reconstruction
Reconstruction is the process of creating an analog voltage (or current) from samples. A digital-to-analog converter takes a series of binary numbers and recreates the voltage (or current) levels that corresponds to that binary number. Then this signal is filtered by a lowpass filter. This process is analogous to interpolating between points on a graph, but it can be shown that under certain conditions the original analog signal can be reconstructed exactly from its samples. Unfortunately, the conditions for exact reconstruction cannot be achieved in practice, and so in practice the reconstruction is an approximation to the original analog signal.

Aliasing
Aliasing is a common problem in digital media processing applications. Many readers have heard of "anti-aliasing" features in high-quality video cards. This page will explain what Aliasing is, and how it can be avoided.

Aliasing is an effect of violating the Nyquist-Shannon sampling theory. During sampling the base band spectrum of the sampled signal is mirrored to every multifold of the sampling frequency. These mirrored spectra are called alias. If the signal spectrum reaches farther than half the sampling frequency base band spectrum and aliases touch each other and the base band spectrum gets superimposed by the first alias spectrum. The easiest way to prevent aliasing is the application of a steep sloped low-pass filter with half the sampling frequency before the conversion. Aliasing can be avoided by keeping Fs>2Fmax.

Nyquist Sampling Rate
The Nyquist Sampling Rate is the lowest sampling rate that can be used without having aliasing. The sampling rate for an analog signal must be at least two times the bandwidth of the signal. So, for example, an audio signal with a bandwidth of 20 kHz must be sampled at least at 40 kHz to avoid aliasing. In audio CD's, the sampling rate is 44.1 kHz, which is about 10% higher than the Nyquist Sampling Rate to allow cheaper reconstruction filters to be used. The Nyquist Sampling Rate is the lowest sampling rate that can be used without having aliasing.

Anti-Aliasing
The sampling rate for an analog signal must be at least two times as high as the highest frequency in the analog signal in order to avoid aliasing. Conversely, for a fixed sampling rate, the highest frequency in the analog signal can be no higher than a half of the sampling rate. Any part of the signal or noise that is higher than a half of the sampling rate will cause aliasing. In order to avoid this problem, the analog signal is usually filtered by a low pass filter prior to being sampled, and this filter is called an anti-aliasing filter. Sometimes the reconstruction filter after a digital-to-analog converter is also called an anti-aliasing filter.

Converters
As a matter of professional interest, we will use this page to briefly discuss Analog-to-Digital (A2D) and Digital-to-Analog (D2A) converters, and how they are related to the field of digital signal processing. Strictly speaking, this page is not important to the core field of DSP, so it can be skipped at the reader's leisure.

A2D converters are the bread and butter of DSP systems. A2D converters change analog electrical data into digital signals through a process called sampling.

D2A converters attempt to create an analog output waveform from a digital signal. However, it is nearly impossible to create a smooth output curve in this manner, so the output waveform is going to have a wide bandwidth, and will have jagged edges. Some techniques, such as interpolation can be used to improve these output waveforms.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text: Digital Signal Processing/Filter Representation


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title: Digital Signal Processing/Quantization


text: Digital Signal Processing/Multirate DSP

title: Digital Signal Processing/Multirate DSP


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Car Washing Techniques/Introduction

Introduction
Maintaining the surface of your vehicle is as important as maintaining the vehicle's engine. A car that runs great and looks good may actually bring in a higher resale value than a vehicle that runs great but has a poor appearance. A clean vehicle's paint will last longer and need fewer expensive repairs than paint that is allowed to become dull and thin due to oxidation.

In today's modern industrial environment the surface of a vehicle is subjected to daily abuse. The sun beats down on your car all day every day, pollutants and dirt deeply embed themselves into your paint, and minute slivers of metal become lodged into your paint which eventually rust. If you have owned a white vehicle or have observed one then you may have noticed specks of rust. Those metal slivers are the cause.

Car washing techniques vary amongst individual vehicle owners. Car washing is an essential function of preventive maintenance. Keeping the exterior of a vehicle clean prevents rust and oxidation and also reduces the occurrence of fine scratches. This article attempts to relay the most common method and the significance of this pastime. Washing a vehicle with soap and a sponge is not the main body of work. In fact, this is only the preparation for the real cleaning. Soap and sponge will not remove all contaminants from a vehicle's surface. Other products will be required such as clay bars, cleaner wax, polish, etc.

It is recommended that you read the section in your owners manual about washing your car. There you will find specific instructions and cautions for cleaning the equipment in your particular model, such as prohibiting the use of acid based wheel cleaners.

In the next section we discuss the various equipment that you will need.

title: Car Washing Techniques/Introduction


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Digital Signal Processing/Sound Processing

Sampling Frequency
Sound in the digital realm is stored in one or more arrays of discrete samples, with each array of samples correlating to a channel (e.g. stereo sound requires two channels, and thus two arrays of samples). The interval of time between each sample is a constant, and is determined by the type of data to be represented. Since we are interested in sound, and the extreme upper limit of human hearing is generally accepted as 20 kHz, the Nyquist-Shannon sampling theorem can be used to determine the interval between samples to accurately re-construct the signals we're interested in.

This theorem states that Exact reconstruction of a continuous-time baseband signal from its samples is possible if the signal is bandlimited and the sampling frequency is greater than twice the signal bandwidth. Essentially what this means is a signal that is limited to a certain range (audible sound: ~20 Hz to 20 kHz) can be reconstructed without error if it is sampled at a rate that is greater than twice the bandwidth. The Red Book audio CD standard sets the sampling rate at 44,100 Hz. This frequency was chosen to leave ample overhead (as required by the Nyquist-Shannon theorem), but could support at least up to 22 kHz.

44.1 kHz is the general standard for sampling rates in digital audio on consumer level equipment, however 48 kHz is common when working with film or video. Also, many recording engineers prefer to record classical or otherwise complex music at 88.2 or 96 kHz—some claim to be able to perceive a difference.

When converting from 48 kHz to 44.1 kHz a sonic blurring effect can sometime occur, because the math is floating point, which is inherently imprecise on a computer. The conversion from 88.2 kHz to 44.1 kHz or 96 kHz to 48 kHz is simpler to perform, since the computer, or device, doing the conversion only has to disregard half the samples. To bypass this problem, a high-quality digital-to-analog converter can be used to bring, for example, a 48 kHz signal back to its analog form, and then is fed into another high-quality analog-to-digital converter to re-sample the signal at 44.1 kHz. This technique is common practice in recording studios where high-end equipment can be trusted to do the conversion flawlessly, however in other situations, the sonic distortion caused by converting the audio in software or hardware may be of little concern.

Bits Per Sample
While sampling frequency determines the time component of an audio signal, the number of bits per sample is used to describe the amplitude. Red Book audio CDs store each sample as a 16 bit signed integer. This means that when an audio signal is converted for use on a CD, each sample's value is quantized as an integer to fit in the range -32768 to +32767.

Wave Files
Wave files contain data which is a representation of audio sound. This format for storing data is an uncompressed format. This means the data can be sent to the digital-to-analog processor for playback without an added step of decompression. This also means that this format will consume a great deal of memory.


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Cognitive Psychology and Cognitive Neuroscience/Behavioural and Neuroscience Methods

Introduction
Behavioural and Neuroscientific methods are used to gain insight into how the brain influences the way individuals think, feel, and act. There are an array of methods, which can be used to analyze the brain and its relationship to behavior. Well-known techniques include EEG (electroencephalography) which records the brain’s electrical activity and fMRI (functional magnetic resonance imaging) which produces detailed images of brain structure and/or activity. Other methods, such as the lesion method, are lesser known, but still influential in today's neuroscience research.

Methods can be organized into the following categories: anatomical, physiological, and functional. Other techniques include modulating brain activity, analyzing behavior or computational modeling.

Lesion method
In the lesion method, patients with brain damage are examined to determine which brain structures are damaged and how this influences the patient's behavior. Researchers attempt to correlate a specific brain area to an observed behavior by using reported experiences and research observations. Researchers may conclude that the loss of functionality in a brain region causes behavioral changes or deficits in task performance. For example, a patient with a lesion in the parietal-temporal-occipital association area will exhibit agraphia, a condition in which he/she is not able to write, despite having no deficits in motor ability. If damage to a particular brain region (structure X) is shown to correlate with a specific change in behavior (behavior Y), researchers may deduce that structure X has a relation to behavior Y.

In humans, lesions are most often caused by tumors or strokes. Through current brain imaging technologies, it is possible to determine which area was damaged during a stroke. Loss of function in the stroke victim may then be correlated with that damaged brain area. While lesion studies in humans have provided key insights into brain organization and function, lesions studies in animals offer many advantages.

First, animals used in research are reared in controlled environmental conditions that limit variability between subjects. Secondly, researchers are able to measure task performance in the same animal, before and after a lesion. This allows for within-subject comparison. And third the control groups can be watched who either did not undergo surgery or who did have surgery in another brain area. These benefits also increase the accuracy of the hypothesis being tested which is more difficult in human research because the before-after comparison and control experiments drop out.

To strengthen conclusions regarding a brain area and task performance, researchers may perform double dissociation. The goal of this method is to prove that two dissociations are independent. Through comparison of two patients with differing brain damage and contradictory disease patterns, researchers may localize different behaviors to each brain area. Broca's area is a region of the brain is responsible for language processing, comprehension and speech production. Patients with a lesion in Broca's area will exhibit Broca's aphasia or non-fluent aphasia. These patients are unable to speak fluently; a sentence produced by a patient with damage to the Broca's area may sound like: "I ... er ... wanted ... ah ... well ... I ... wanted to ... er ... go surfing ... and ..er ... well...". On the other hand, Wernicke's area is responsible for speech comprehension. A patient with a lesion in this area has Wernicke's aphasia. They may be able to produce language, but lack the ability to produce meaningful sentences. Patients may produce 'word salad': " I then did this chingo for some hours after my dazi went through meek and been sharko". Patients with Wernicke's aphasia are often unaware of speech deficits and may believe that they are speaking properly.

Certainly one of the famous "lesion" cases was that of Phineas Gage. On 13 September 1848 Gage, a railroad construction foreman, was using an iron rod to tamp an explosive charge into a body of rock when premature explosion of the charge blew the rod through his left jaw and out the top of his head. Miraculously, Gage survived, but reportedly underwent a dramatic personality change as a result of destruction of one or both of his frontal lobes. The uniqueness of Gage case (and the ethical impossibility of repeating the treatment in other patients) makes it difficult to draw generalizations from it, but it does illustrate the core idea behind the lesion method. Further problems stem from the persistent distortions in published accounts of Gage—see the Wikipedia article Phineas Gage.

CAT
CAT scanning was invented in 1972 by the British engineer Godfrey N. Hounsfield and the South African (later American) physicist Alan Cromack.

CAT (Computed Axial Tomography) is an x-ray procedure which combines many x-ray images with the aid of a computer to generate cross-sectional views, and when needed 3D images of the internal organs and structures of the human body. A large donut-shaped x-ray machine takes x-ray images at many different angles around the body. Those images are processed by a computer to produce cross-sectional picture of the body. In each of these pictures the body is seen as an x-ray ‘slice’ of the body, which is recorded on a film. This recorded image is called a tomogram.

CAT scans are performed to analyze, for example, the head, where traumatic injuries (such as blood clots or skull fractures), tumors, and infections can be identified. In the spine the bony structure of the vertebrae can be accurately defined, as can the anatomy of the spinal cord. CAT scans are also extremely helpful in defining body organ anatomy, including visualizing the liver, gallbladder, pancreas, spleen, aorta, kidneys, uterus, and ovaries. The amount of radiation a person receives during a CAT scan is minimal. In men and non-pregnant women it has not been shown to produce any adverse effects. However, doing a CAT test hides some risks. If the subject or the patient is pregnant it maybe recommended to do another type of exam to reduce the possible risk of exposing her fetus to radiation. Also in cases of asthma or allergies it is recommended to avoid this type of scanning. Since the CAT scan requires a contrast medium, there's a slight risk of an allergic reaction to the contrast medium. Having certain medical conditions; Diabetes, asthma, heart disease, kidney problems or thyroid conditions also increases the risk of a reaction to contrast medium.

MRI
Although CAT scanning was a breakthrough, in many cases it was substituted by magnetic resonance imaging (MRI), a method of looking inside the body without using x-rays, harmful dyes or surgery. Instead, radio waves and a strong magnetic field are used in order to provide remarkably clear and detailed pictures of internal organs and tissues. History and Development of MRI

MRI is based on a physics phenomenon called nuclear magnetic resonance (NMR), which was discovered in the 1930s by Felix Bloch (working at Stanford University) and Edward Purcell (from Harvard University). In this resonance, magnetic field and radio waves cause atoms to give off tiny radio signals. In the year 1970, Raymond Damadian, a medical doctor and research scientist, discovered the basis for using magnetic resonance imaging as a tool for medical diagnosis. Four years later a patent was granted, which was the world's first patent issued in the field of MRI. In 1977, Dr. Damadian completed the construction of the first “whole-body” MRI scanner, which he called the ”Indomitable”. The medical use of magnetic resonance imaging has developed rapidly. The first MRI equipment in healthcare was available at the beginning of the 1980s. In 2002, approximately 22,000 MRI scanners were in use worldwide, and more than 60 million MRI examinations were performed.

Common Uses of the MRI Procedure

Because of its detailed and clear pictures, MRI is widely used to diagnose sports-related injuries, especially those affecting the knee, elbow, shoulder, hip and wrist. Furthermore, MRI of the heart, aorta and blood vessels is a fast, non-invasive tool for diagnosing artery disease and heart problems. The doctors can even examine the size of the heart-chambers and determine the extent of damage caused by a heart disease or a heart attack. Organs like lungs, liver or spleen can also be examined in high detail with MRI. Because no radiation exposure is involved, MRI is often the preferred diagnostic tool for examination of the male and female reproductive systems, pelvis and hips and the bladder.

Risks

An undetected metal implant may be affected by the strong magnetic field. MRI is generally avoided in the first 12 weeks of pregnancy. Scientists usually use other methods of imaging, such as ultrasound, on pregnant women unless there is a strong medical reason to use MRI.

PPT MRIII
There has been some further development of the MRI: The DT-MRI (diffusion tensor magnetic resonance imaging) enables the measurement of the restricted diffusion of water in tissue and gives a 3-dimensional image of it. History: The principle of using a magnetic field to measure diffusion was already described in 1965 by the chemist Edward O. Stejskal and John E. Tanner. After the development of the MRI, Michael Moseley introduced the principle into MR Imaging in 1984 and further fundamental work was done by Dennis LeBihan in 1985. In 1994 the engineer Peter J. Basser published optimized mathematical models of an older diffusion-tensor model. This model is commonly used today and supported by all new MRI-devices.

The DT-MRI technique takes advantage of the fact that the mobility of water molecules in brain tissue is restricted by obstacles like cell membranes. In nerve fibers mobility is only possible alongside the axons. So measuring the diffusion gives rise to the course of the main nerve fibers. All the data of one diffusion-tensor are too much to process in a single image, so there are different techniques for visualization of different aspects of this data: - Cross section images - tractography (reconstruction of main nerve fibers) - tensor glyphs (complete illustration of diffusion-tensor information)

The diffusion manner changes by patients with specific diseases of the central nervous system in a characteristic way, so they can be discerned by the diffusion-tensor technique. Diagnosis of apoplectic strokes and medical research of diseases involving changes of the white matter, like Alzheimer's disease or Multiple sclerosis are the main applications. Disadvantages of DT-MRI are that it is far more time consuming than ordinary MRI and produces large amounts of data, which first have to be visualized by the different methods to be interpreted.

fMRI
The fMRI (Functional Magnetic Resonance) Imaging is based on the Nuclear magnetic resonance (NMR). The way this method works is the following: All atomic nuclei with an odd number of protons have a nuclear spin. A strong magnetic field is put around the tested object which aligns all spins parallel or antiparallel to it. There is a resonance to an oscillating magnetic field at a specific frequency, which can be computed in dependence on the atom type (the nuclei’s usual spin is disturbed, which induces a voltage s (t), afterwards they return to the equilibrium state). At this level different tissues can be identified, but there is no information about their location. Consequently the magnetic field’s strength is gradually changed, thereby there is a correspondence between frequency and location and with the help of Fourier analysis we can get one-dimensional location information. Combining several such methods as the Fourier analysis it is possible to get a 3D image. The central idea for fMRI is to look at the areas with increased blood flow. Hemoglobin disturbs the magnetic imaging, so areas with an increased blood oxygen level dependant (BOLD) can be identified. Higher BOLD signal intensities arise from decreases in the concentration of deoxygenated haemoglobin. An fMRI experiment usually lasts 1-2 hours. The subject will lie in the magnet and a particular form of stimulation will be set up and MRI images of the subject's brain are taken. In the first step a high resolution single scan is taken. This is used later as a background for highlighting the brain areas which were activated by the stimulus. In the next step a series of low resolution scans are taken over time, for example, 150 scans, one every 5 seconds. For some of these scans, the stimulus will be presented, and for some of the scans, the stimulus will be absent. The low resolution brain images in the two cases can be compared, to see which parts of the brain were activated by the stimulus. The rest of the analysis is done using a series of tools which correct distortions in the images, remove the effect of the subject moving their head during the experiment, and compare the low resolution images taken when the stimulus was off with those taken when it was on. The final statistical image shows up bright in those parts of the brain which were activated by this experiment. These activated areas are then shown as coloured blobs on top of the original high resolution scan. This image can also be rendered in 3D.

fMRI has moderately good spatial resolution and bad temporal resolution since one fMRI frame is about 2 seconds long. However, the temporal response of the blood supply, which is the basis of fMRI, is poor relative to the electrical signals that define neuronal communication. Therefore, some research groups are working around this issue by combining fMRI with data collection techniques such as electroencephalography (EEG) or magneto encephalography (MEG), which has much higher temporal resolution but rather poorer spatial resolution.

PET
Positron emission tomography, also called PET imaging or a PET scan, is a diagnostic examination that involves the acquisition of physiologic images based on the detection of radiation from the emission of positrons. It is currently the most effective way to check for cancer recurrences. Positrons are tiny particles emitted from a radioactive substance administered to the patient. This radiopharmaceutical is injected to the patient and its emissions are measured by a PET scanner. A PET scanner consists of an array of detectors that surround the patient. Using the gamma ray signals given off by the injected radionuclide, PET measures the amount of metabolic activity at a site in the body and a computer reassembles the signals into images. PET's ability to measure metabolism is very useful in diagnosing Altsheimer's disease, Parkinson's disease, epilepsy and other neurological conditions, because it can precisely illustrate areas where brain activity differs from the norm. It is also one of the most accurate methods available to localize areas of the brain causing epileptic seizures and to determine if surgery is a treatment option. PET is often used in conjunction with an MRI or CT scan through "fusion" to give a full three-dimensional view of an organ.

Electromagnetic Recording Methods
The methods we have mentioned up to now examine the metabolic activity of the brain. But there are also other cases in which one wants to measure electrical activity of the brain or the magnetic fields produced by the electrical activity. The methods we discussed so far do a great job of identifying where activity is occurring in the brain. A disadvantage of these methods is that they do not measure brain activity on a millisecond-by-millisecond basis. This measuring can be done by electromagnetic recording methods, for example by single-cell recording or the Electroencephalography (EEG). These methods measure the brain activity really fast and over a longer period of time so that they can give a really good temporal resolution.

Single cell
When using the single-cell method an electrode is placed into a cell of the brain on which we want to focus our attention. Now, it is possible for the experimenter to record the electrical output of the cell that is contacted by the exposed electrode tip. That is useful for studying the underlying ion currents which are responsible for the cell’s resting potential. The researchers’ goal is then to determine for example, if the cell responds to sensory information from only specific details of the world or from many stimuli. So we could determine whether the cell is sensitive to input in only one sensory modality or is multimodal in sensitivity. One can also find out which properties of a stimulus make cells in those regions fire. Furthermore we can find out if the animal’s attention towards a certain stimulus influences in the cell’s respond.

Single cell studies are not very helpful for studying the human brain, since it is too invasive to be a common method. Hence, this method is most often used in animals. There are just a few cases in which the single-cell recording is also applied in humans. People with epilepsy sometimes get removed the epileptic tissue. A week before surgery electrodes are implanted into the brain or get placed on the surface of the brain during the surgery to better isolate the source of seizure activity. So using this method one can decrease the possibility that useful tissues will be removed. Due to the limitations of this method in humans there are other methods which measure electrical activity. Those we are going to discuss next.

EEG

One of the most famous techniques to study brain activity is probably the Electroencephalography (EEG). Most people might know it as a technique which is used clinically to detect aberrant activity such as epilepsy and disorders.

Electroencephalogram (Electroencephalography, EEG) is obtained by electro-electron electroencephalography, which collects weak creatures produced by the human brain from the scalp and enlarges notes. Measuring electroencephalogram, and EEG measures, voltage fluctuations generated by the flow of ionic neurons in the brain. EEG is a diagnosis of a brain-related disease, but because it is susceptible to interference, it is usually used in combination with other methods.

EEG is most commonly used to diagnose epilepsy because epilepsy can cause abnormal EEG readings. It is also used to diagnose sleep disorders, coma, cerebrovascular disease, etc., and brain death. Brain waves have been used in first-line methods to diagnose tumors, strokes, and other focal brain diseases, but this has been reduced with the advent of high-resolution anatomical imaging techniques, such as nuclear magnetic resonance (MRI). And computed tomography (CT). Unlike CT and MRI, EEGs have a higher temporal resolution. Therefore, although spatial resolution of EEG is limited, it is still a valuable tool for research and diagnostics, especially when determining studies that require time resolution in the millisecond range

In an experimental way this technique is used to show the brain activity in certain psychological states, such as alertness or drowsiness. To measure the brain activity mental electrodes are placed on the scalp. Each electrode, also known as lead, makes a recording of its own. Next, a reference is needed which provides a baseline, to compare this value with each of the recording electrodes. This electrode must not cover muscles because its contractions are induced by electrical signals. Usually it is placed at the “mastoid bone” which is located behind the ear.

During the EEG electrodes are places like this. Over the right hemisphere electrodes are labelled with even numbers. Odd numbers are used for those on the left hemisphere. Those on the midline are labelled with a z. The capital letters stands for the location of the electrode(C=central, F=frontal, Fop= frontal pole, O= occipital, P= parietal and T= temporal). After placing each electrode at the right position, the electrical potential can be measured. This electrical potential has a particular voltage and furthermore a particular frequency. Accordingly, to a person’s state the frequency and form of the EEG signal can differ. If a person is awake, beta activity can be recognized, which means that the frequency is relatively fast. Just before someone falls asleep one can observe alpha activity, which has a slower frequency. The slowest frequencies are called delta activity, which occur during sleep. Patients who suffer epilepsy show an increase of the amplitude of firing that can be observed on the EEG record. In addition EEG can also be used to help answering experimental questions. In the case of emotion for example, one can see that there is a greater alpha suppression over the right frontal areas than over the left ones, in the case of depression. One can conclude from this, that depression is accompanied by greater activation of right frontal regions than of left frontal regions.

The disadvantage of EEG is that the electric conductivity, and therefore the measured electrical potentials vary widely from person to person and, also during time. This is because all tissues (brain matter, blood, bones etc.) have other conductivities for electrical signals. That is why it is sometimes not clear from which exact brain-region the electrical signal comes from.

ERP
Whereas EEG recordings provide a continuous measure of brain activity, event-related potentials (ERPs) are recordings which are linked to the occurrence of an event. A presentation of a stimulus for example would be such an event. When a stimulus is presented, the electrodes, which are placed on a person’s scalp, record changes in the brain generated by the thousands of neurons under the electrodes. By measuring the brain's response to an event we can learn how different types of information are processed. Representing the word eats or bake for example causes a positive potential at about 200msec. From this one can conclude, that our brain processes these words 200 ms after presenting it. This positive potential is followed by a negative one at about 400ms. This one is also called N400 (whereas N stands for negative and 400 for the time). So in general one can say that there is a letter P or N to denote whether the deflection of the electrical signal is positive or negative. And a number, which represent, on average, how many hundreds of milliseconds after stimulus presentation the component appears. The event-related- potential shows special interest for researchers, because different components of the response indicate different aspects of cognitive processing. For example, presenting the sentences “The cats won’t eat” and “The cat won’t bake”, the N400 response for the word “eat” is smaller than for the word “bake”. From this one can draw the conclusion that our brain needs 400 ms to register information about a word’s meaning. Furthermore, one can figure out where this activity occurs in the brain, namely if one looks at the position on the scalp of the electrodes that pick up the largest response.

MEG
Magnetoencephalography (MEG) is related to electroencephalography (EEG). However, instead of recording electrical potentials on the scalp, it uses magnetic potentials near the scalp to index brain activity. To locate a dipole, the magnetic field can be used, because the dipole shows excellently the intensity of the magnetic field. By using devices called SQUIDs (superconducting quantum interference device) one can record these magnetic fields.

MEG is mainly used to localize the source of epileptic activity and to locate primary sensory cortices. This is helpful because by locating them they can be avoided during neurological intervention. Furthermore, MEG can be used to understand more about the neurophysiology underlying psychiatric disorders such as schizophrenia. In addition, MEG can also be used to examine a variety of cognitive processes, such as language, object recognition and spatial processing among others, in people who are neurologically intact.

MEG has some advantages over EEG. First, magnetic fields are less influenced than electrical currents by conduction through brain tissues, cerebral spinal fluid, the skull and scalp. Second, the strength of the magnetic field can tell us information about how deep within the brain the source is located. However, MEG also has some disadvantages. The magnetic field in the brain is about 100 million times smaller than that of the earth. Due to this, shielded rooms, made out of aluminum, are required. This makes MEG more expensive. Another disadvantage is that MEG cannot detect activity of cells with certain orientations within the brain. For example, magnetic fields created by cells with long axes radial to the surface will be invisible.

TMS
History: Transcranial magnetic stimulation (TMS) is an important technique for modulating brain activity. The first modern TMS device was developed by Antony Baker in the year 1985 in Sheffield after 8 years of research. The field has developed rapidly since then with many researchers using TMS in order to study a variety of brain functions. Today, researchers also try to develop clinical applications of TMS, because there are long lasting effects on the brain activity it has been considered as a possible alternative to antidepressant medication.

Method: UMTS utilizes the principle of electromagnetic induction to an isolated brain region. A wire-coil electromagnet is held upon the fixed head of the subject. When inducing small, localized, and reversible changes in the living brain tissue, especially the directly under laying parts of the motor cortex can be effected. By altering the firing-patterns of the neurons, the influenced brain area is disabled. The repetitive TMS (rTMS) describes, as the name reveals, the application of many short electrical stimulations with a high frequency and is more common than TMS. The effects of this procedure last up to weeks and the method is in most cases used in combination with measuring methods, for example: to study the effects in detail.

Application: The TMS-method gives more evidence about the functionality of certain brain areas than measuring methods on their own. It was a very helpful method in mapping the motor cortex. For example: While rTMS is applied to the prefrontal cortex, the patient is not able to build up short term memory. That determines the prefrontal cortex, to be directly involved in the process of short term memory. By contrast measuring methods on their own, can only investigate a correlation between the processes. Since even earlier researches were aware that TMS could cause suppression of visual perception, speech arrest, and paraesthesias, TMS has been used to map specific brain functions in areas other than motor cortex. Several groups have applied TMS to the study of visual information processing, language production, memory, attention, reaction time and even more subtle brain functions such as mood and emotion. Yet long time effects of TMS on the brain have not been investigated properly, Therefore experiments are not yet made in deeper brain regions like the hypothalamus or the hippocampus on humans. Although the potential utility of TMS as a treatment tool in various neuropsychiatric disorders is rapidly increasing, its use in depression is the most extensively studied clinical applications to date. For instance in the year 1994, George and Wassermann hypothesized that intermittent stimulation of important prefrontal cortical brain regions might also cause downstream changes in neuronal function that would result in an antidepressant response. Here again, the methods effects are not clear enough to use it in clinical treatments today. Although it is too early at this point to tell whether TMS has long lasting therapeutic effects, this tool has clearly opened up new hopes for clinical exploration and treatment of various psychiatric conditions. Further work in understanding normal mental phenomena and how TMS affects these areas appears to be crucial for advancement. A critically important area that will ultimately guide clinical parameters is to combine TMS with functional imaging to directly monitor TMS effects on the brain. Since it appears that TMS at different frequencies has divergent effects on brain activity, TMS with functional brain imaging will be helpful to better delineate not only the behavioral neuropsychology of various psychiatric syndromes, but also some of the pathophysiologic circuits in the brain.

tDCS
transcranial Direct Current Stimulation: The principle of tDCS is similar to the technique of TMS. Like TMS this is a non-invasive and painless method of stimulation. The excitability of brain regions is modulated by the application of a weak electrical current.

History and development: It was first observed that electrical current applied to the skull lead to an alleviation of pain. Scribonius Largus, the court physician to the Roman emperor Claudius, found that the current released by the electric ray has positive effects on headaches. In the Middle Ages the same property of another fish, the electrical catfish, was used to treat epilepsy. Around 1800, the so-called galvanism (it was concerned with effects of today’s electrophysiology) came up. Scientists like Giovanni Aldini experimented with electrical effects on the brain. A medical application of his findings was the treatment of melancholy. During the twentieth century among neurologists and psychiatrists electrical stimulation was a controversial but nevertheless wide spread method for the treatment of several kinds of mental disorders (e.g. Electroconvulsive therapy by Ugo Cerletti).

Mechanism: The tDCS works by fixation of two electrodes on the skull. About 50 percent of the direct current applied to the skull reaches the brain. The current applied by a direct current battery usually is around 1 to 2 mA. The modulation of activity of the brain regions is dependent on the value of current, on the duration of stimulation and on the direction of current flow. While the former two mainly have an effect on the strength of modulation and its permanence beyond the actual stimulation, the latter differentiates the modulation itself. The direction of the current (anodic or cathodic) is defined by the polarity and position of the electrodes. Within tDCS two distinct ways of stimulation exist. With the anodal stimulation the anode is put near the brain region to be stimulated and analogue for the cathodal stimulation the cathode is placed near the target region. The effect of the anodal stimulation is that the positive charge leads to depolarization in the membrane potential of the applied brain regions, whereas hyperpolarisation occurs in the case of cathodal stimulation due to the negative charge applied. The brain activity thereby is modulated. Anodal stimulation leads to a generally higher activity in the stimulated brain region. This result can also be verified with MRI scans, where an increased blood flow in the target region indicates a successful anodal stimulation.

Applications: From the description of the TMS method it is should be obvious that there are various fields of appliances. They reach from identifying and pulling together brain regions with cognitive functions to the treatment of mental disorders. Compared to TMS it is an advantage of tDCS to not only is able to modulate brain activity by decreasing it but also to have the possibility to increase the activity of a target brain region. Therefore the method could provide an even better suitable treatment of mental disorders such as depression. The tDCS method has also already proven helpful for apoplectic stroke patients by advancing the motor skills.

Behavioural Methods
Besides using methods to measure the brain’s physiology and anatomy, it is also important to have techniques for analyzing behaviour in order to get a better insight on cognition. Compared to the neuroscientific methods, which concentrate on neuronal activity of the brain regions, behavioural methods focus on overt behaviour of a test person. This can be realized by well defined behavioural methods (e.g. eye-tracking), test batteries (e.g. IQ-test) or measurements which are designed to answer specific questions concerning the behaviour of humans. Furthermore, behavioural methods are often used in combination with all kinds of neuroscientific methods mentioned above. Whenever there is an overt reaction on a stimulus (e.g. picture) these behavioural methods can be useful. Another goal of a behavioural test is to examine in what terms damage of the central nervous system influences cognitive abilities.

A Concept of a behavioural test
The tests are performed to give an answer to certain questions about human behaviour. In order to find an answer to that question, a test strategy has to be developed. First it has to be carefully considered, how to design the test in the best way, so that the measurement results provide an accurate answer to the initial question. How can the test be conducted so that founding variables are minimal and the focus really is on the problem? When an appropriate test arrangement is found, the defining of test variables is the next part. The test is now conducted and probably repeated until a sufficient amount of data is collected. The next step is the evaluation of the resulting data, with the suitable methods of statistics. If the test reveals a significant result, it might be the case that further questions arise about neuronal activity underlying the behaviour. Then neuroscientific methods are useful to investigate correlating brain activities. Methods, which proved to provide good evidence to a certain recurrent question about cognitive abilities of subjects, can bring together in a test battery.

Example: Question: Does a noisy surrounding affect the ability to solve a certain problem?

Possible test design: Expose half of the subject to a silent environment while solving the same task as the other half in a noisy environment. In this example founding variables might be different cognitive abilities of the participants. Test variables could be the time needed to solve the problem and the loudness of the noise etc. If statistical evaluation shows significance: Probable further questions: How does noise affect the brain activities on a neuronal level?

Are you interested in doing a behavioural test on your own, visit: the socialpsychology.org website.

Test batteries
A neuropsychological assessment utilizes test batteries that give an overview on a person’s cognitive strengths and weaknesses by analyzing various cognitive abilities. A neuropsychological test battery is used by a neuropsychologist to assess brain dysfunctions that can rise from developmental, neurological or psychiatric issues. Such batteries can appraise various mental functions and the overall intelligence of a person.

Firstly, there are test batteries designed to assess whether a person suffers from a brain damage or not. They generally work well in discriminating those with brain damage from neurologically impaired patients, but worse when it comes to discriminating them from those with psychiatric disorders. The most popular test, Halstead-Reitan battery, assesses abilities ranging from basic sensory processing to complex reasoning. Furthermore, the Halstead-Reitan battery provides information on the cause of the damage, the brain areas that were harmed, and the stage the damage has reached. Such information is valuable in developing a rehabilitation program. Another test battery, the Luria-Nebraska battery, is twice as fast to administer as the Halstead-Reitan. Its subtests are ordered according to twelve content scales (e.g. motor functions, reading, memory etc.). These two test batteries do not focus only on the absolute level of performance, but look at the qualitative manner of performance as well. This allows for a more comprehensive understanding of the cognitive impairment.

Another type of test batteries, the so-called IQ tests, aims to measure the overall cognitive performance of an individual. The most commonly used tests for estimating intelligence are the Wechsler family intelligence tests. Age-appropriate test versions exist for small children from age 2 years and 6 months, school-aged children, and adults. For example, the Wechsler Intelligence Scale for Children, fifth edition (WISC-V) measures various cognitive abilities in children between 6 and 16 years of age. The test consists of multiple subtests that form five different main indexes of cognitive performance. These main constructs are verbal reasoning skills, inductive reasoning skills, visuo-spatial processing, processing speed and working memory. Performance is analyzed both compared to a normative sample of similarly aged peers and within the test subject, assessing personal strengths and weaknesses.

The Eye Tracking Procedure
Another important procedure for analyzing behavior and cognition is Eye-tracking. This is a procedure of measuring either where we are looking (the point of gaze) or the motion of an eye relative to the head. There are different techniques for measuring the movement of the eyes and the instrument that does the tracking is called the tracker. The first non-intrusive tracker was invented by George Buswell.

The eye tracking is a study with a long history, starting back in the 1800s. In 1879 Louis Emile Javal noticed that reading does not involve smooth sweeping of the eye along the text but rather series of short stops which are called fixations. This observation is one of the first attempts to examine the eye’s directions of interest. The book of Alfred L. Yarbus which he published in 1967 after an important eye tracking research is one of the most quoted eye tracking publications ever. The eye tracking procedure is not that complicated. Video based eye trackers are frequently used. A camera focuses on one or both eyes and records the movements while the viewer looks at some stimulus. The most modern eye trackers use contrast to locate the center of the pupil and create corneal reflections using infrared or near-infrared non-collimated light.

There are also two general types of eye tracking techniques. The first one – the Bright Pupil is an effect close to the red eye effect and it appears when the illuminator source is onset from the optical path while when the source is offset from the optical path, the pupil appears to be dark (Dark Pupil). The Bright Pupil creates great contrast between the iris and the pupil which allows tracking in light conditions from dark to very bright but it is not effective for outdoor tracking. There are also different eye tracking setup techniques. Some are head mounted, some require the head to be stable, and some automatically track the head during motion. The sampling rate of the most of them is 30 Hz. But when we have rapid eye movement, for example during reading, the tracker must run at 240, 350 or even 1000-1250 Hz in order to capture the details of the movement. Eye movements are divided to fixations and saccades. When the eye movement pauses in a certain position there is a fixation and saccade when it moves to another position. The resulting series of fixations and saccades is called a scan path. Interestingly most information from the eye is received during a fixation and not during a saccade. Fixation lasts about 200 ms during reading a text and about 350 ms during viewing of a scene and a saccade towards new goal takes about 200 ms. Scan paths are used in analyzing cognitive intent, interest and salience.

Eye tracking has a wide range of application – it is used to study a variety of cognitive processes, mostly visual perception and language processing. It is also used in human-computer interactions. It is also helpful for marketing and medical research. In recent years the eye tracking has generated a great deal of interest in the commercial sector. The commercial eye tracking studies present a target stimulus to consumers while a tracker is used to record the movement of the eye. Some of the latest applications are in the field of the automotive design. Eye tracking can analyze a driver’s level of attentiveness while driving and prevent drowsiness from causing accidents.

Modeling Brain-Behaviour
Another major method, which is used in cognitive neuroscience, is the use of neural networks (computer modelling techniques) in order to simulate the action of the brain and its processes. These models help researchers to test theories of neuropsychological functioning and to derive principles viewing brain-behaviour relationships. In order to simulate mental functions in humans, a variety of computational models can be used. The basic component of most such models is a “unit”, which one can imagine as showing neuron-like behaviour. These units receive input from other units, which are summed to produce a net input. The net input to a unit is then transformed into that unit’s output, mostly utilizing a sigmoid function. These units are connected together forming layers. Most models consist of an input layer, an output layer and a “hidden” layer as you can see on the right side. The input layer simulates the taking up of information from the outside world, the output layer simulates the response of the system and the “hidden” layer is responsible for the transformations, which are necessary to perform the computation under investigation. The units of different layers are connected via connection weights, which show the degree of influence that a unit in one level has on the unit in another one.

The most interesting and important about these models is that they are able to "learn" without being provided specific rules. This ability to “learn” can be compared to the human ability e.g. to learn the native language, because there is nobody who tells one “the rules” in order to be able to learn this one. The computational models learn by extracting the regularity of relationships with repeated exposure. This exposure occurs then via “training” in which input patterns are provided over and over again. The adjustment of “the connection weights between units” as already mentioned above is responsible for learning within the system. Learning occurs because of changes in the interrelationships between units, which occurrence is thought to be similar in the nervous system.


text: Digital Signal Processing/Digital Signal Processors


text:
Car Washing Techniques/Equipment

Equipment
There are a number of items that aid in making car-washing an enjoyable and convenient practice. Old clothes and shoes are recommended in order to avoid soiling preferred clothing. If the weather feels hot then it is preferable to wait until later in the afternoon. The vehicle could also be relocated to a shaded area such as under a tree, but do not leave a clean vehicle under a tree overnight as a combination of tree sap, pollen, and fallen leaves may collect on it. If the weather is too cold, then the risk of contracting hypothermia (or simply experiencing discomfort) exists, and the water may freeze onto the car. Also, if rain is forecasted for when the vehicle is scheduled to be washed or for shortly after, then postpone until the threat of rain has passed. A fresh dose of rain can leave dirt and water spots — grayish circles that form on the vehicle after a rainstorm.

The most common car-washing equipment:

 * 1) Two clean buckets. One bucket has the car-washing soap and the other bucket has water for rinsing the sponge in order to avoid washing your car with dirty water.
 * 2) A sponge or wash mitt made of thick soft foam (not a dishwashing sponge). Diapers, cloths, shirts, etc. are not recommended.
 * 3) Some car-washing soap. Never use dish detergents; they are far too harsh and will strip any applications of wax. Another reason to not use dish or laundry detergent is that they are harder to rinse off with cold water and may therefore leave soap scum behind.
 * 4) A water hose that is long enough to reach around the vehicle without having to be draped over the trunk or hood.
 * 5) A chamois, which is a super-absorbent cloth that does not leave lint on the vehicle.

 * The Auto Detailing Wiki -
 * The Detailing FAQ -
 * Waterless car cleaners -

title: Car Washing Techniques/Equipment


text:
Talk:Cognitive Psychology and Cognitive Neuroscience/Knowledge Representation and Hemispheric Specialisation

HI Anna, tschuldigung dass ich noch nicht früher geschrieben habe...

Also zu eurem Text: Als erstes erst einmal ist euer Text zu kurz, Schmalhofer will 500Wörter und ihr habt bloß 201 ( das ganze kann man einfach in Word unter Extras und 'Wörter zählen' finden!). Ich weiß, dass es schwierig ist den Text schon so lang zu haben ohne die Kapitel geschrieben zu haben. Aber an sich ist euer Text inhaltich schon gut, womit ich meine, dass ihr eine gute Ahnung zu scheinen habt, worüber ihr schreiben werdet. Was ich noch verbessern würde, ist die Verbindung der einzelnen Absätze. Sie hören sich noch nicht flüssig in einander überlaufend an (Wie in einem Buch solls halt sein). So könnt ihr auch noch ne Menge Wörter gut machen. Ich hoffe ihr habt nicht mehr zu viel Arbeit hier mit! Bei weiteren Fragen fragt halt nochma nach! LG Imme

Hallo, es ist irgendwie schwer für uns ein Review zu schreiben wenn ihr ständig updates macht. Wir wollen natürlich immer über die neuste Version von euch was schreiben, damit das dann nicht schon wieder veraltert ist. Außerdem ist eure erste Version ja nicht so wirklich viel gewesen. Wär schön wenn ihr kurz schreiben könntet bis wann ihr soweit fertig seid, dass wir n review schreiben können?

mfg sven

Hallo, lass dich nicht täuschen, es wird im text inhaltlich ja nicht so viel verändert, dadurch wird dein review auch nicht viel besser. mfg ips

Hi all of you. You have a very good beginning, but in the middle you should invest some work. You've got the most colorful chapter so far :D I like it :) --Aschoeke 12:10, 17 August 2006 (UTC)


text:
Car Washing Techniques/Location

Location
After the proper equipment has been gathered, the vehicle needs to be in a proper location (preferably in a shaded area, away from direct sunlight). A flat, dry, and clean surface such as a driveway or parking lot is prime; however, a gravel lot that is relatively clean will suffice. If neither are accessible, surfaces such as grass or dirt will work; however, mud may splash onto the vehicle when the hose is aimed at the tires. If the vehicle is washed on grass or dirt then the vehicle should be left until the ground and vehicle are both dry before the vehicle is moved.

title: Car Washing Techniques/Location


text:
Car Washing Techniques/Procedure

Procedure
Wash, wax and detail in the following order:
 * 1) Brush, vacuum, and clean the interior. Either prior to, after, or on the same day.
 * 2) Clean wheels and tires. To avoid splash back from the wheels.  Also, use tire brushes and never use them for the body of the car!
 * 3) Wash exterior
 * 4) Apply tire dressing
 * 5) Polish wheels
 * 6) Clean & Treat exterior trim
 * 7) Polish and then wax exterior paints

Clean the interior
Because washing a vehicle thoroughly can be an all day job you can opt to clean the interior the day before or the day after. It would depend on how much discipline you have. See the Detailing Wiki article on interior cleaning for more info.

Washing the Paintwork
In order to avoid deep scratches, the vehicle must be rinsed thoroughly before a sponge is applied. To do this, always begin at the top of the vehicle and rinse down. If the weather is particularly hot that day, the process will most likely require repeating, even after just a few minutes. Always make sure that the section of the vehicle that is being washed is wet. If possible park the car in a shady area. Also, morning or afternoon are preferable times.

Pour a liberal amount of soap into the bucket (making sure it is free of debris first) and then fill it up with water. Follow the manufacturers recommended instructions for which quantities of soap and water to use. Dip the sponge into the water and wait for it to absorb as much soapy water as it can. Squeeze the sponge repeatedly while swirling it around in the water. Squeeze excess water out of the sponge and then apply it to the roof of the vehicle. Always wipe the vehicle's surface in straight motions (to avoid making fine swirl marks), remember to begin with the roof and work down the sides to the bottom of the vehicle. If the weather is hot, then soap the vehicle in small sections (I.E. a panel at a time), and then rinse immediately. If not, the heat can dry the soap onto the vehicle's paint.

Washing the Wheels
It is highly recommended to use a different set of equipment (sponge, bucket etc.) for the wheels. This will reduce the risk of scratching other parts of the paint work, as the wheels are usually the dirtiest part of a vehicle.

There are two common ways to clean the wheels of a vehicle.

The first way is to clean them with soap and a wheel brush. The choice of brush rests largely on the design of the hubcaps or wheels.

First, ensure that the wheels have been rinsed with water. Next, scrub them with the wheel brush being careful not scratch the hubcaps' paint. Note: hubcaps with grooves in them can contain a lot of brake dust, as can alloy wheels. These problem areas can require extra time and scrubbing.

The second method is to use spray on, rinse off chemicals. Directions for these should be found on the bottle.

Rinsing and drying the vehicle
An important step is rinsing all of the soap off of the vehicle. Begin at the top and spray downward to avoid splashing soap back up to the top of the vehicle. If your finish has a good coat of wax, make your final rinse with water of a moderate volume and low pressure about an inch above the surface rather than a high pressure spray. This will create a sheet of water producing fewer small water beads and will improve your drying results.

Afterward, dry the vehicle with a clean, plush microfiber towel. Microfiber towels are superior to chamois or terry towels and will prevent new scratches from appearing in the paint. As much as possible, dry the vehicle thoroughly including the nooks and crannies (door jambs, under the hood, trunk lid, etc.) to prevent water spots and premature corrosion. It is not recommended to allow the vehicle to dry naturally as minerals in the water will be left behind as the water itself evaporates.

Polishing
Many products are available on the market which claim to polish paint to restore luster. Some are more effective than others, consult your owners manual or vehicle manufacturer for a recommendation for your particular car. A popular polishing tool with many enthusiasts is the clay bar. Most polishes should be applied sparingly, usually no more than once or twice per year. Never use a polishing compound on a car with a clear coat. These compounds are far too abrasive and will remove the clear coat.

To use a clay bar, the surface of the vehicle must always be lubricated. Never rub the bar on dry paint, it will scratch. Additionally, if the clay bar is dropped on the ground, it must be discarded. The contamination it picks up would subsequently be ground into the paint if it continues to be used.

Waxing
Most car wash solutions claim to have wax in them, however the amount they contain is usually not enough to offer significant protection to your vehicle. It is therefore recommended that a "hard" wax be used. These can come in a variety of forms, including pastes, liquids, and sprays. If water applied to your paint forms very large droplets or does not bead at all, it should be waxed. A general rule of thumb is to apply wax when the beads become larger than 2.5 centimeters (1 in).

Since there are a wide variety of products, follow the instructions for application on your particular product. Apply wax to one section of the car at a time, and let haze. Once this occurs, remove the wax by buffing with a folded microfiber towel. Changing to different folds often will make removal of the excess wax easier. After removal, it may be necessary to open the doors to remove wax residue at the edges of the panels.

External References

 * The Detailing Wiki -
 * The Detailing FAQ -

title: Car Washing Techniques/Procedure


text:
Car Washing Techniques/End Result

End result
Car-washing is an activity often referenced in movies, songs, and other media. Keeping a clean vehicle goes a long way toward improving the appearance of the vehicle, even if it is a few years old. Regular washing and waxing will prolong the shine of the vehicle's paint.

Other Resources

 * The Auto Detailing Wiki -
 * The Detailing FAQ -

title: Car Washing Techniques/End Result


text:
Talk:Cognitive Psychology and Cognitive Neuroscience/Cognitive Psychology and the Brain

Wie verprochen nochmal ein Review bevor ihr die Bewertung fuer euer Kapitel bekommt. Neben der Tatsache, die euch bestimmt bewusst ist, dass ihr noch zu wenig an Text auf der Seite stehen habt, ist die Einleitung und auch der Schlussteil sehr gut geworden. Im mittleren Teil waren die Formulierungen in Englisch noch zu Deutsch, ich habe versucht das etwas zu verbessern ohne euren Text an sich zu aendern. Trotzdem ist der Teil noch etwas zu stueckelig. Ideen fuer irgendwelche Bilder? Ich denke das muesste hier einfacher sein als z.B. fuer die Decision Making group. Achja nicht uebertreiben mit den Verlinkungen zu Wikipedia (z.B. Romans sind keine Bereicherung fuer das Thema 'Cognitive Psychology and the Brain'). --Iroewer 18:10, 10 August 2006 (UTC)

Hi, der Eintrag vom 12:04, 27 July 2006 88.73.105.62 (Talk) ist von mir (Imme). Wenn es also Fragen gibt richtet euch an mich. Der Inhalt ist immer noch derselbe aber ich habe die Formulierungen verbessert --Iroewer 12:10, 27 July 2006 (UTC)

Hi ihr!! Ihr habt zwar mit den drei Unterbereichen 'Einführung', 'methods' und 'populations of research participants' genug Worte zusammen (Schmalhofer möchte 500), aber der Stil stimmt so noch nicht. Ihr zeigt zwar, dass ihr eine Idee habt was ihr schreiben wollt, aber diese 'Introduction' soll auch die für das Buch später sein. Daher soll diese Einführung schon einmal das Konzept eures Themas behandeln und zwar in einem fließenden Text! Schreibt nicht im Wikipedia stil über die verschiedenen Teile, vergisst nicht es soll ein Buch werden! Bei weiteren Fragen wendet euch eifnach an mich! LG Imme

So, what about brain anatomy? Methods is in chapter 4, btw. I think we should rather make the "and the brain" part the center of this chapter. First explaining the crucial role it plays in cognitive psychology and thereby explaining what cogpsy actually is (we could put the history part in there, something like in behaviourism there was no brain and then there come cogpsy), then going ahead and introducing its functions (or parts, or both). What do you think about that? Written by User:Tkrieger, copied by --Aschoeke 21:53, 28 April 2006 (UTC)

Ich wollte nur anmerken, dass selbst "fließende Text"e manchmal Überschriften besitzen und nicht nur Wikipediaartikel in Sinnabschnitte zergliedert sind sondern auch Bücher(und selbst Einleitungen zu Büchern). Vielen aufrichtigen dank für die konstruktiven Hinweise, ich werde vesuchen sie zu beherzigen. Merlin

moinsn Ich hab das nicht mehr weitergeschrieben, als ich sah, was Merlin im laufe des Abends hochgeladen hatte. Trotzdem wollte ich das veröffentlichen, sei's nur für ein paar Stunden. Vielleicht lässt sich das alles ja auch igendwie zusammenbasteln. Da ich mittendrin aufgehört hab, ist es noch nicht sehr ausgefeilt, besonders das Beispiel gefällt mir noch nicht ganz. Weitergehen sollte die Geschichte mit der Erläuterung ein paar kognitiver Funktionen, ein bisschen wie bei Goldstein, und so zum thema "brain" überleiten. Was haltet ihr davon, es so zu machen? Oder ist es nicht scientific genug? please comment. Alex.

Grüß Gott! Also ich finde das cool was du geschrieben hast und man kann doch gut darauf aufbauen. Wieso hat mein Upload dich unterbrochen? Passt doch alles ganz gut zusammen und es ist ja auch ein ganz anderes Thema wie das was ich geschrieben habe... Findest du, dass das nicht zusammen passt? Ich würde sagen, dass du das unbedingt stehen lassen solltest. Es würde sich doch anbieten von dort aus zur "History" überzuleiten und von dort zum Hirnkaschterl an sich... was ist deine/eure Meinung? Grüße Merlin.

So, ich finde ich habe meinen Teil beigetragen. Wir haben jetzt viel zu viele Wörter, 1489, um genau zu sein. Ich hab das nicht alles zusammenbringen können, also irgendwas muss raus. Ich überlass das euch, macht mit meinem Text was ihr wollt, ich hoffe das guckt sich noch jemand vor 12 an. schöne grüße, Alex.

Sodele... Der dialektische Dialog als Wesen des Wikigedankens nimmt ja langsam Form an. Hab die Überschriften wieder eingeführt, weil es ohne einfach scheiße ist. Den Table of contents können wir ja erstmal ausgeblended lassen, damit sich niemand an einen Wikipediaartikel erinnert fühlt... Ich finde wir sollten aber noch an der inhaltlichen Aussagekraft des BUCHkapitels arbeiten. Vielleicht könnten wir auch was über ethische Verantwortung schreiben, hab mal nen link zu den "ethic code" der APA hinzugefügt. Grüße merlin

 * Kleiner Tipp für Diskussionen. Um einen Faden reinzubringen, kann man den Text mit Doppelpunkten einrücken. Dadurch kann man dann besser sehem worauf man sich bezieht.
 * Nur so als Beispiel
 * --Aschoeke 15:37, 3 May 2006 (UTC)

Hey, I'm an American student. I have a BA in Psychology. I made minor type fixes and altered some sentence structure and a few word choices. I will continue to do this unless asked not to. Thanx, and keep up the good work!

AkumAPRIME

Sources in text
The sources need to be explicitly stated inside of the text. There are some issues with language usage which makes some of the skews facts. I changed a few areas to more accuratly represent the truth, such as the fact that Chomsky wasn't the only reason for the fall of behavioral dominance in America; just one of the major reasons.


text:
User:Jaberwocky6669~enwikibooks

I will improve this page in time. But for now go here: User:Jaberwocky6669

title: User:Jaberwocky6669~enwikibooks


text:
Immigrating to Canada/Refugee Class

Canada admits refugees under its "Refugee and Humanitarian Resettlement Program".

There are three recognized classes of refugees:
 * 1) Convention Refugees Abroad Class
 * 2) Country of Asylum Class
 * 3) Source Country Class

Eligibility
A person falls into the Convention Refugees Abroad class where they:
 * 1) are a Convention Refugee
 * 2) live outside of Canada
 * 3) are seeking to resettle in Canada
 * 4) cannot return to country of residence/nationality
 * 5) cannot integrate into country of first asylum
 * 6) do not have another offer to resettle elsewhere

A person falls within the Country of Asylum class is a person where they:
 * 1) live outside country of citizenship
 * 2) continues to be affected by armed conflict
 * 3) cannot find adequate solution to the situation in a reasonable time

A person falls within the Source Country class where:
 * 1) reside in a designated "source country" which is the country of nationality or residency
 * 2)  continues to be affected by armed conflict.

title: Immigrating to Canada/Refugee Class


text:
Talk:Cognitive Psychology and Cognitive Neuroscience/Evolutionary Perspective on Social Cognitions

Hi there! Your Introduction has a nice form. But you still have not enough words (just 220)! You can let them count in WORD, EXTRAS and 'Wörter zählen'. As you probably know you need 500 words! Maybe explain the different *points a bit more already in the introduction. Lg Iroewer

Wo ist denn euer Text??? Gruppen wie 'Overall Structure' und 'Crossreferences' sind abhaengig davon, dass euer Text, auch wenn er noch nicht ganz fertig ist, schon ins Internet ladet!! Es waere auch moeglich gewesen noch ein Review zu bekommen bzw. dass andere auch von ausserhalb ihren Anteil liefern. Das ist ja der eigentliche Sinn an einem solchen Projekten!! Iroewer


text:
Talk:Cognitive Psychology and Cognitive Neuroscience/Behavioural and Neuroscience Methods

Hey, some notes... First the good parts. The collection of themes are good. You get a lot of information in a clear way.

Just some hints before the final date: What you still need are pictures. Either pictures of our brain, there are many colorful pictures or the machines themselves. Maybe you could show the difference between the old x-ray pictures in comparison to today's modern ones. A part I didn't quite understand was the part about MRI. What is the difference with parallel and antiparallel magnetic fields. Maybe it would be possible for you to somehow rewrite this part. Another suggestion would be that you have some kind of sum up of the used techniques and when they are applied. This could be as well done at the beginning. It would be nicer to have a more open beginning as it is for example done in the first chapter. Here you could introduce a patient and discuss which method would be probably the right one. "Der rote Faden" couldn't be found in your text, but I'm aware that it is quite hard to get evolution and usefulness into this chapter. But what might me still possible is to draw some connection to other chapters. For example in which of the psychological research is which method used. If you have still questions just ask! Iroewer

Hi there! Your text is definetly not long enough! You just have 162 words, but you need 500. Just try to explain the methods a bit further. Don't forget this will be an introduction to a chapter of a book. Lg Iroewer

Hey, 2 notes. A) I don't know how to properly link. If someone could link the name Phineas Gage to it's Wiki page without a url sitting there, that would be great. B) I used my personal knowledge and several google sites to write my little blurb. What, if anything, should I cite as a reference?

2 things
Hey, 2 notes. A) I don't know how to properly link. If someone could link the name Phineas Gage to it's Wiki page without a url sitting there, that would be great. B) I used my personal knowledge and several google sites to write my little blurb. What, if anything, should I cite as a reference?

Experimental Techniques
Hey, if you need an additional link, here are Experimental Techniques link to London's INSTITUTE OF COGNITIVE NEUROSCIENCE on the main link page. Just an useful hint, I hope... Iroewer

2 Images uploaded, 2 to come :) --Aschoeke 12:58, 18 August 2006 (UTC)


text:
Wikijunior:Big Book of Fun Science Experiments/Red cabbage indicator

An acid and base indicator is a chemical that shows whether different chemicals are acids (like lemon juice) or bases (like baking powder). This is called a chemical's pH. You can make an indicator using red cabbage juice. The cabbage juice changes color depending on how acidic or basic (alkaline) the chemical is. The pH level is indicated by the amount of hydrogen (the "H" in "pH") ions in the tested chemical. Hydrogen ions are protons that had their electrons stripped off them (since hydrogen atoms consist of one proton and one electron).

We often use a test like this to make sure swimming pools are kept at the right pH. If the water in a swimming pool is too acidic or too basic (alkaline), it can damage pool equipment, bathing suits, or stop the chlorine that keeps pools clean from working properly.

pH is measured on a scale of 1 to 14. Neutral chemicals have a pH of 7. Acidic chemicals have a pH of 1-6. Basic (alkaline) chemicals have a pH of 8-14.

Safety
As with all experiments, you should always get help from an adult. Some acids and bases can hurt your skin, so you should wear: If you get chemicals on your hands or gloves, do not touch your eyes! Wash your hands after completing the experiment.
 * Rubber gloves
 * An apron
 * Safety glasses (regular glasses, sunglasses or swimming goggles are okay if you don't have safety glasses).

What You Need

 * A red cabbage
 * A knife or grater
 * A medium sized bowl
 * At least 4 small cups
 * Chemicals to test such as lemon juice and baking powder or soda
 * coffee filter

Step 1

 * Have a parent, guardian, or teacher help you cut or grate between a quarter or a half of the cabbage into small pieces.
 * Put the cabbage into a medium sized bowl.
 * Pour water over the cabbage. You can use cold water, warm or boiling water. Boiling water will work the fastest, but only boil the water if you have an adult to help you.
 * Let the cabbage sit in the water for a while (30-45 minutes), until the water turns a deep purple colour. You can stir the mixture to speed up the process.

Step 2

 * Using a coffee filter or a fine sieve, strain the juice into a cup. It should be deep bluish purple in colour.
 * Pour equal amounts of the strained liquid into small plastic cups. These are your 'test tubes' in which you will test different chemicals.

Step 3

 * Set one of your cups ('test tubes') aside. This is your control. It already contains water, which usually has a pH of 7. This means that water is neither an acid nor a base.
 * Assemble some testing chemicals (some good ones to try are below).
 * Label each cup with the name of the test chemical each cup will contain, so you will remember what you put in each cup.
 * Which chemical do you think is the most acidic?

Step 4

 * Pour, drip or spoon a small quantity of each test chemical into the cup labeled with its name.
 * Observe the change in colour of the juice. If the juice turns reddish, the chemical you are testing is an acid. If the water turns bluish, the chemical you are testing is a base. If it stays the same, the chemical is neutral, like water.

Some Chemicals to Test

 * Lemon juice
 * Baking powder or soda
 * Milk
 * Yogurt
 * Vinegar
 * Soap

Observations

 * Arrange your cups from red, to pink, to violet, to purple, to blue, and to green. You might not have all of these colors, but that's okay.
 * The cup that is most red is the most acidic. The cup that is the most blue or green is the most basic (alkaline). Which chemical is the most acidic? Which is the most basic (alkaline)?


text:
Talk:Blender 3D: Noob to Pro/Quickie Model

I'm new to Blender and also I don't use Wikibooks, and I'd feel weird editing something when I'm just a stranger, but they never tell you to switch to vertex mode. If I haven't done 3D modeling before, I would've been very lost. From the previous lesson, you're working with the faces. And this one introduces vertexes without even telling them to switch.

=3D Transform Widgets= Has the name changed? This page refers to "3D Transform Widgets" but it looks to me like this is now called "Use 3D Transform Manipulator". --DuLithgow 23:13, 26 July 2006 (UTC)

The hand icon mentioned in the quickie model page is a hand with only one finger up. I'm currently using os x so it may be different in this version.

Hand icon needs to be updated
I'm using Blender 2.42a (Ubuntu Linux 6.10 packaged version), and the 3D transform manipulator is represented by a hand with just one finger up. The image needs to be updated.

Axis indicator lock
Selecting "Active Object" Didn't prevent the blue dot and arrows (axis indicators) from going onto the vertex I wish to select. I used "3D Cursor" instead, making the indicators remain in the center, since the 3D cursor is there.

Using version 2.43 on Kubuntu 7.04.

= Selecting vertices =

I've tidied up the sentence about vertex colours in non-default GUI themes, but I'm not sure it even needs to be there. This guide is for noobs, right? So I don't think it's right to start confusing people with the suggestion of changing themes etc. as it distracts the reader from the point. Anyway I've tidied the sentence up. Chop it out, I say.

Redundant Page
This page has been almost completely covered by earlier pages in the guide. Perhaps it should be taken out and those other pages updated with the video, and some of the details that this page has?

As a newbie, I basically skipped over it, due to the earlier hands-on version of this page. There were a couple of tidbits that hadn't been covered, but with the earlier instruction sets under my belt, I didn't need this page.

I know.. it's up to me to change it, but I'm totally new to blender, so I'm not going to presume that I know better about what and how I need to learn the information. SO I'm just putting this out there, in the hopes that wiser heads will prevail. --Deadguy (talk) 13:29, 26 August 2009 (UTC)

This page could use a few more images to go along with the text.Rhettro (talk) 21:57, 10 June 2010 (UTC)

Doesn't Work
If you extrude downwards and then merge the top it'll also merge the middle for some reason. This probably has something to do with the fact that when you select only the top vertices, both edges are selected on the vertical side. I got around this by just making a ring after making it taller and then joining the top.

More links to show "Howtos".
For some operations ancillary to the modelling, more explanations or more links to How-Tos should be provided: See: [1. Turn 'Occlude Background Geometry' off, so you can see all vertices. Note, in newer versions, this button is called "Limit Selection to Visible." It is one of the buttons to the right of transform orientation which is to the right of the mode select which should be currently set to "edit mode".] This step needs a link to a section that describes the buttons being referred to, or at least the display of icons to look for to effect the operation.