Samarth Patel
email: samarth3@ualberta.ca

Pamila Viswanathan

Trends in Multimedia Research

Over the years, tremendous progress has been achieved in many areas of multimedia research. Multimedia technology is widely applied everywhere and there exists a need for improvement due to the emerging technology and increase of data. In this paper we look into few of the many areas of research like Teleconferencing, Pose Estimation and Gesture Recognition, Medical Segmentation, Object Tracking etc.

Publication Review

A. Teleconferencing

1.Enhancing Videoconferencing Using Spatially Varying Sensing

In this paper [START_REF] Basu | Enhancing videoconferencing using spatially varying sensing[END_REF] authors introduce a system for enhancing videoconferencing by using a compression system that incorporates multiple and moving foveae and combining information from them. Moreover, they also propose using spatially varying sensing as a pre-processor to JPEG. The authors propose using Variable Resolution transform to image compression, like the human visual system where in an area of interest has higher resolution and the peripheral scene has lower resolution. Moreover, Cartesian VR transform is used where the distortion factor is fixed, and the shape of the foveae is dependent entirely on its absolute location in the image and its position relative to other foveae. Moving foveae can be implemented on important feature such as mouth, eyes in a videoconferencing call to compress efficiently. Moreover, the model is extended to accommodate multiple foveae (cooperative and competitive foveae) and distortions. Furthermore, the concept of cooperative foveae is generalized as:

l actual = 1 N -1 j=0
1 d power j × N -1 i=0 l i d power i (1)
Where N is the number of foveae, power is the power with which weights corresponding to distances d i are applied to l i .The results observed after applying the technique as a pre-processor for JPEG are:

• JPEG with quality=1 after compression without VR: 3798 bytes (98.55% compression) and SNR RMS of 18.25 • JPEG enhanced by VR pre-processor : 377 bytes (98.56%) compression and the SNR rms is 47.23.

Variable Resolution Teleconferencing

The author in this paper [START_REF] Basu | Variable resolution teleconferencing[END_REF] describes the Variable Resolution (VR) based image compression and a few new interpolation methods are outlined with comparison between them. The VR transformation has high resolution in the fovea and low resolution in the periphery. It has two parameters -compression and alpha ( -distortion in the edges). A pixel in polar coordinates are mapped to VR coordinates. The drawback in this is that the transformed images are not rectangular. A multi scaling factor is implied so that each will have maximum distance to the edge of the image and can be mapped to a rectangle. Sometimes there will be multiple foveas, in this case a location point is found in the two estimated points and then weights are added according to the distance from the point to the fovea. The compression performance is determined by compression ratio, time and quality. The effect of if low, then the compression is high. If is high then there is optimal compression. The new interpolation method depends on three aspects. One is generation of compression image, next is compressed final image last is the algorithm used to find the 'nearest neighbour'. The nearest neighbour algorithm usually worked outwards to look for neighbouring pixels. This was modified to work on both the directions starting from the centre. Instead of computing each pixel in the compressed image, the pixel is computed as the average of all the pixels around it. For uncompressing they use the bi-linear method which uses the 4 nearest samples to find the pixel value. A comparison is done using a variety of combination of the method described. By adding more computation to the original method, the results can be improved. An intraframe difference coding to find the difference between two successive frames and to transmit only the difference. Also, no special boards are needed to perform this technique.

Panoramic Video with Predictive Windows for Telepresence Applications

In this paper [START_REF] Baldwin | Panoramic video with predictive windows for telepresence applications[END_REF] the authors propose applying predictive Kalman filter to predict the fragment of a frame that is to be transmitted in a panoramic image taken using a CCD camera and conic mirror. The Kalman predictor is applied to a mouse modelled as:

mx = F -bx.
where m is the mass, F is the external force applied and b is the coefficient of friction. Moreover, the Error covariance matrices Q k for process noise and R k for measurement noise are of the form:

Q k = diag(q k 2 , q k 2 , q k 2 ) and R k = diag(r k 2 , r k 2 ).
Here the values for qk and rk are determined by combination of techniques used in [START_REF] Emura | Compensation of time lag between actual and virtual spaces by multi-sensor integration[END_REF][START_REF] Liang | On temporal-spatial realism in the virtual reality environment[END_REF]. Moreover, the warping process takes images provided by the camera and based on point-of-view, field-of -view and aspect ratio, creates flat images that could be taken from a cylindrical view. Here the warping process uses a simple transformation to keep the processing time small. The prediction system predicts the likely position of the mouse in the next step and prepares the next fragment accordingly. In order to get efficient performance from the system the authors try to mitigate each of the three factors affecting response delays:

• Delay in capturing the next frame from the video stream with. capture time varying between 0.033 seconds to 0.0143 seconds.

• Transmission time 0.15 seconds for grey scale image of 320 by 240 pixels.

• Client Side Processing: 0.05 seconds.

B. Pose Estimation and Gesture Recognition

Pose Recognition using Random Transform

The author proposes a novel method in [START_REF] Singh | Pose recognition using the Radon transform[END_REF] for human pose recognition using the Randon Transform. There are other approaches used for pose recognition but they all need normalization and are also expensive. They propose a method without normalization and guarantees high resolution of leg and arm poses. Although Hough transform (HT) and Randon Transform (RT) are used in various pattern recognition systems, due to some of the back draws in the HT they have used RT along with spatial maxima mapping. Their technique depends on two assumptions, ie., any pose of the arm or leg can be replaced by the medial skeleton of that pose and the pose in RT space provides the pose classification information. The technique is divided into five steps. 1) The images are acquired and the background separation is done using the statistical background modelling approach. This provies a binary image of the arm and leg which are again process to fill any holes present in the foreground.

2) These binary images undergo thinning to form a medial skeleton. 3) RT is used to detect the orientation of the skeleton. As in most cases the maxima are not localized or slightly diffused, they have included a threshold value to get the local maxima. The RT is then binarized as if RT value is greater or equal to the threshold the it is 1 else 0. An image dilation operation is performed on this so that there are no disconnected regions. The centroid location of each maxima is calculated and stored as f. 4) RT for a known pose B and unknown test pose T and its corresponding centroids are B and T . A one to one mapping is perform between the known and unknown pose. This is done for finding the maxima within a threshold limit. If a maxima is found then it a 'hit' else is a 'miss'. The score is calculated from the ratio of hit to miss. 5) If the score is high then T is assigned as the same pose as B.

Nose shape estimation and tracking for model-based coding

In this paper [START_REF] Yin | Nose shape estimation and tracking for model-based coding[END_REF], the author proposes a nose shape detection method. This method limits search regions and provides a fix for shrinking effect of deformable templates using shape adaptive model. The nostril and nose side shapes detection and tracking is based on individual deformable templates. [START_REF] Yin | Integrating active face tracking with model based coding[END_REF] is used for tracking the head movement. In this paper a two stage algorithm is developed for feature center locationglobal region growing and local region growing. In the former, a large threshold is set to detect the dark regions in the face while ignoring the rest. The face region is examined by selecting the center point in the head as a seed pixel. If the size of the growing region is determined within a range and the skin region is found. Later blobs (facial, top bottom) are found which are formed as four groups by performing vertical and horizontal clustering. In the later part, a small threshold is set to detect the facial organs. The feature center and its surrounding area is the local area of that feature.

Here rather than the color they take the luminance to set a small growing threshold. The feature region of the organs are extracted from the binary image. After the features are detected, the shape of the eye is found using the Hough Transform (iris position and size). For the nose, the nostrils shape is detected using a geometric template( twisted pair curve). The width is determined by finding the distance of both the curves, the orientation by eigen vectors and the shape is controlled by a parameter which ranges between 1 to 10. The nose side is estimated using a vertical parabola. Finally a 3D wireframe is matched on the face to track the facial movements.

A Multisensor Technique for Gesture Recognition Through Intelligent Skeletal Pose Analysis

In the paper [START_REF] Rossol | A Multisensor Technique for Gesture Recognition Through Intelligent Skeletal Pose Analysis[END_REF] a novel technique for gesture recognition is proposed using multisensor based intelligent skeletal pose analysis. One of the primary problems tackled by the authors is estimation of hand poses when then hand is not directly facing camera, or parts of it are occluded such as in the case of a pinch gesture where some fingers are occluded by others which could prevent accurate gesture recognition. In the proposed method the optimal pose is estimated using a trained support vector machine, which is built once with a training set which uses a feature vector composed of subsets of each sensor's output. Subsequently each sensor's pose output is converted into global coordinate system to represent the poses of all fingers in a single unified space, while also keeping the positions of all fingers in local coordinate system, finally both the local and global hand pose information are input into the gesture recognition model. Compared to single sensor-based approach with a mean pose estimation error of 15.48 the proposed method has mean pose estimation of 10.60. This method is 90.8% optimal in terms of reducing the mean pose estimation error. Moreover, for correctly classified instances the median difference between pose estimations was 11.44mm and for incorrectly classified instances the median difference was 4.47mm, indicating that in cases of large disagreements between two sensors, the proposed approach often made the correct decision.

C. Object Tracking

Eye Tracking and Animation for MPEG-4 Coding

This paper [START_REF] Bernogger | Eye tracking and animation for MPEG-4 coding[END_REF] discusses on the eye detection and tracking in a model based approach. The eye movement is detected by using Hough Transform and deformable template matching similar to the feature detection in [START_REF] Chow | Towards a System for Automatic Facial Feature Detection[END_REF]. In the proposed algorithm the face region is detected and that the upper right and upper left coarse regions can be used to detect the eyes. The iris of the eyes is detected using the Hough Transform. The intensity image obtained is convolved with a Sobel filter and all the edges with lower magnitude is eliminated. The exact center of the iris is got by the Hough Transform. The eye model described in this paper has parameters shown in the figure. The potential energy is created by matching deformable templates using two images. The template is positioned approximately relative to the iris. The h1 and h2 parameters are then approximated. h1 is given more importance as the upper eyelid has more movements. The horizontal integral projection along with the gradient projections in both the directions, the eyelid position is estimated. The eyelid are then matched to the deformable template. In the tracking of the eye movements the position and size of the eye are restricted to the previous frame also the matched template will be used to initialize the next template. For the animation of eyes, 11 feature vertices are used in each eye to match the corresponding feature points on the template. The iris animation is done by matching the center if the iris model with the center of the eye image. The eyelid animations are also done by matching the feature vertices of the model to that of the image. Its displacement consist of feature motion vectors and non-feature motion vector are found by interpolation the feature vectors that are around them.

Based on these vertices a deformed eye model is built for each frame. Finally, the eye movements of the model are synthesized by texture mapping the original image.

Integrating active face tracking with model based coding

This paper [START_REF] Yin | Integrating active face tracking with model based coding[END_REF] proposes a system for tracking a face with an active camera using model based coding approach. The proposed algorithm can be divided into 4 major steps. 1) Initially a background compensation is performed to estimate the relationship of the pixels in a 3D point in images taken at different camera orientations. In this process only the camera coordinates and the image plane have changes in direction. The pixel in the previous image could be calculated by finding the pixel position in the current image.

2) This paper points the necessity to get a head silhouette from a set of frames. The difference between the current and previous frames are found and the absolute value is taken as a threshold. Morphological filtering is applied to remove the noise and multiple frames are integrated using frame motion fusion algorithm called motion mask (MM). To fuse the consecutive masks a spatiotemporal filter is used. It is then smoothened more by the spatial median filter. Threshold is set as 1 and is applied to the fused image. Further a morphological filter is applied to smoothen the image and by using the gradient operator the edges are detected.

3) The facial features are then detected using deformable template matching and exploit color information. The eye detection has been explained in [START_REF] Bernogger | Eye tracking and animation for MPEG-4 coding[END_REF]. The mouth detection is done by fining the region of interest. The approximation of the lip is got from the color information which is then localized using deformable templates. 4) The facial model adaptation is done from two image views. As the shape of the head is known, the eyes and the mouth can determine the face position. A 3D wireframe model is fitted into the facial information extracted using an energy minimization procedure.

D. Medical Segmentation

1. Automatic Segmentation of Spinal Cord MRI Using Symmetric Boundary Tracing In this paper [START_REF] Mukherjee | Automatic segmentation of spinal cord MRI using symmetric boundary tracing[END_REF], the authors propose a fully automated active contour tracing algorithm for extraction of spinal cord from MRI Here the image is first Unskewed as a precursor to segmentation of other targets. After drawing a circle at the centre of mass of the spinal cord region, Using the Bhattacharya coefficient between the intensity histograms of sectors, the two sectors obtained by drawing a diameter in the circle are matched. After the image is Unskewed, an evolved active trace algorithm is applied to segment the muscle region. The failure of correct tracing caused by uniform search regions of each active trace point along its normal direction is solved by using temporal constraint in order to introduce variable search space for each active trace point along its orthogonal direction. The overall complexity is O(nm 3 ). Compared to existing methods which extract only the spinal cord, this approach segments the neighbouring regions of interest providing better visual guidance for the Intraspinal micro stimulation (ISMS) implant.

Gradient Vector Flow based Active Shape Model for Lung Field Segmentation in Chest Radiographs

The paper [START_REF] Xu | Gradient Vector Flow based Active Shape Model for Lung Field Segmentation in Chest Radiographs[END_REF] explains the Gradient Vector Flow (GVF) with Active Shape Model (ASM) -a high level method to accurately segment the lung field from chest radiographs. This paper explains three types of previous related work. 1) PDM generation -There are two models in this approach, shape model and profile model. The shape model is formed form a sset of training images. The principal component analysis id done to approximate the training dataset. In the profile model, the PCA is done to get the grey level variation parameters. 2) ASM based segmentation -a PDM is performed to estimate the contours that are near to the lung field in the test image. Matches are found between the control points found above to the target points. A displacement is done to calculate the shape of the model. 3) GVF-ASM Segmentation -Along with the ASM segmentation, a GVF calculator to find the edge map and GVF-based points evaluation to add both magnitude and direction. In the proposed method, it overcomes the blurring in the edges of the contour field as the magnitude and gradient vectors changes smoothly by proposing a new points evaluation equation:

C = C + w • sgn(g(C )) • e -g(C ) (2)
This helps to decrease the smoothness in the contour edges and gives point to strong edges. In comparison with the GVF-ASM segmentation, the proposed method when there is a change in parameters is still accurate in the edges and the other is sensitive to parameter selection. It is also proven that the proposed method is more stable and accurate whereas the GVF-ASM has a strong ringing effect and moves away from the edges.

Other Fields

1. Modelling Fish-Eye Lens In this paper [START_REF] Basu | Modeling fish-eye lenses[END_REF] the author proposes a variable resolution transformation based on the characteristics of fish-eyes without using any sensors. There are two methods described for modelling fish-eye lens. Firstly, the introduced Fish-Eye transformation (FET) generates a high resolution in the fovea and a low resolution in the periphery. It also points out the anisotropic distortion present in the peripheral regions of the image. Given various distortion parameter , different fish-eye transformation images is generated. Secondly, the Polynomial Fish-Eye Transformation (PFET). In this paper, PFET modelling of data is done by fitting a set of observation to a model which is a polynomial. It is similar to FET except that it includes the radial distance for undistorted images. The optical center of the distortion, called the focus of distortion (FD) is found by the average minimum curvature of the intersection of the lines Using FD, the measure of the average of the distortion in all four directions are obtained. Using the polynomial function and a set of data pairs and the Gauss-Jordan elimination method is used for finding the average distortion The degree of the polynomial uses the variance of the model and the fitted data. For FET as the unknown coefficients are nonlinear with the equation, instead of Gauss-Jordan, Newton's method is used. The PFET shows a better approximation but FET can easily modify distortion by and can restore the original image using inverse function but not in PFET 2. Stereo Matching Using Random Walks This paper [START_REF] Shen | Stereo matching using random walks[END_REF] presents a novel approach for stereo matching using random walks (RW). It is a two-step process where in the first step a set of reliable matching pixels are determined using RW and in the second, using these reliable points the disparity of unreliable pixels are determined. The Random walks is a graph representation of an image where the probability of a walker from an unlabelled node to a labelled node is calculated which is equal to the Dirichlet problem. The prior matrices are built according to the illumination in the image and the accuracy of the resulting disparity maps are performed by the Laplacian matrix. In this process, the Laplacian matrix and the prior matrix are built first. If the brightness is low, then the similarity difference between the pixels will be small, hence an average luminance value is used for the measurement of brightness. A left-right checking is done to the set of reliable pixels. Its process is similar to [START_REF] Lei | Region-tree based stereo using dynamic programming optimization[END_REF] which results in a set of matched pixels (M) and the rest as unreliable set (U). The textureless regions have similar pixels around its neighbours so a low disparity is obtained, which is incorrect. After the left-right checking, every pixel goes through a disparity validation test. Finally the disparity of unreliable pixels are computed by solving the Dirichlet problem. The drawback in this is that it works only in YCbCr space, so it is limited to color images.

A Framework for Adaptive Training and Games in Virtual Reality Rehabilitation Environments

In the paper [START_REF] Rossol | A framework for adaptive training and games in virtual reality rehabilitation environments[END_REF] the authors propose a low-cost, lowmaintenance, high availability, system for training people with disabilities in the use of powered wheelchair using virtual reality, moreover they also propose an approach using Bayesian networks to enable adaptive training in virtual rehabilitation environment. The system consists of training program that adaptively changes difficulty according to the performance of the patient thus taking into account the range of disabilities and residual capabilities that the patient may have, and also an XML scene node-based framework as a 3D-modelling plug-in tool for clinician to design and alter position, scale, rotation of objects in the training space to customize the environment to patient need based on their assessments. Moreover, the adaptive system modelled using Bayesian networks can be easily extended to include large number of latent and measured variable with complex interactions between them. During tests, the system was found to effective with a mean time of 81.4 seconds for experimental group that was trained using this system before their attempt to complete a short obstacle course using a powered wheelchair compared to a mean time of 104.5 seconds for the group that did not receive any training with this system.

Interactive Multimedia for Adaptive Online Education

In this paper the authors propose an Interactive Multimedia program based on a novel CROME (Computer Reinforced Online Multimedia Education) framework which integrates all main component of education i.e learning, teaching, and testing. The proposed system is capable of adaptively altering the difficulty of questions during testing. Moreover, also consists of custom-designed modules for tracking precise concepts, Computer assisted question item-authoring. The proposed incorporates rich interactive elements tailored to the content for instance students are presented chemical equations with 3D objects that they can interact with, moreover it is also capable of drag and drop interaction for both 2D and 3D objects, It has language items that combine acoustic and visual effects to help students relate semantics to spellings and pronunciations. The proposed system is implemented using Java 2D/3D applets, JavaScript, PHP and MySQL following the principles of portability, Reusability, Interoperability, and Scalability.

5. Variable-resolution character thinning The paper introduces a variable resolution character thinning approach modelled after the working of human eye, in the sense that the foveae is higher resolution compared to periphery. The proposed algorithm is parallel and uses a 9x9 window with a high resolution 3x3 centre and low-resolution periphery. The resolution is reduced by a ratio of 9:2 in the periphery. Here all character pixels are first examined by Guo's algorithm A1 [START_REF] Guo | Parallel thinning with two sub iteration algorithms[END_REF], while also comparing each character pixel with a 3x3 template. If certain constraints are satisfied, then another set of 9x9 templates are used. Here the centre part is a regular 3x3 template, while each of the eight peripheral parts also covers a 3x3 region, but at reduced resolution. Each peripheral region generates two binary values α and β, where β is used to record some special pattern of pixel arrangement in the 3x3 region. The results indicate that the proposed approach of variable resolution character thinning performs better in accurately thinning the given character by preserving the straight lines in the characters compared to other approaches such as Holt's method and Guo's method.

Figure 1 .

 1 Figure 1. Overview of system

Figure 2 .

 2 Figure 2. Deformable template model of the eye


Yasir Mansoor Kundi

Shakir Sardar

Kamal Badar

Linking performance pressure to employee work engagement: the moderating role of emotional stability

Keywords: Performance pressure, Threat appraisal, Challenge appraisal, Emotional stability, Work engagement

Purpose -The purpose of this paper is to investigate the mediating role of threat and challenge appraisals in the relationship between performance pressure and employees' work engagement, as well as the buffering role of emotional stability, as a personal characteristic, in this process. Design/methodology/approach -Data were collected using a three-wave research design. Hypotheses were examined with a sample of 247 white-collar employees from French organizations. Findings -Performance pressure is appraised as either threat or challenge. Challenge appraisal positively mediated the performance pressure and work engagement relationship, whereas threat appraisal negatively mediated the performance pressure and work engagement relationship. Emotional stability moderated these effects, suggesting performance pressure was appraised as a challenge rather than a threat, which then enhanced employee work engagement. Practical implications -This study has shown that employees with high emotional stability who perceived performance pressure as a challenge achieved stronger employee work engagement. Originality/value -Building on Lazare's theory of stress and Mitchell et al. 's theorization, this research demonstrates mediating and moderating mechanisms driving the role of performance pressure on employee work engagement relationships.

Introduction

Work engagement À "a positive, fulfilling, work-related state of mind, that is characterized by vigor, dedication, and absorption" (Schaufeli et al., 2002, p. 74), has emerged as a significant construct in the management literature because it has been shown to promote a variety of not only the employee but also organizational outcomes. Job satisfaction, organizational citizenship behavior, organizational engagement and low turnover intentions [START_REF] Aboramadan | Does transformational leadership better predict workrelated outcomes than transactional leadership in the NPO context? Evidence from Italy[END_REF][START_REF] Albrecht | Personality, self-efficacy and job resources and their associations with employee engagement, affective commitment and turnover intentions[END_REF][START_REF] Rai | Exploring the mediating role of work engagement between the linkages of job characteristics with organizational engagement and job satisfaction[END_REF] have been reported as the examples of these outcomes. The growing interest in work engagement gives rise to the need for a better understanding of its antecedents [START_REF] Matsuo | Effect of learning goal orientation on work engagement through job crafting: a moderated mediation approach[END_REF]. Although numerous factors have been examined as antecedents (e.g. personality traits, learning goal orientation, personal resources and job autonomy), performance-related antecedents of work engagement have so far received very little attention in the existing literature. Only recently, research began to address questions concerning whether employees facing demands for high performance increase or decrease their work engagement [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF][START_REF] Zhang | Exploring the effects of job autonomy on engagement and creativity: the moderating role of performance pressure and learning goal orientation[END_REF]. Thus, only a narrow spectrum of the performance-related antecedents of work engagement has been considered, especially in terms of performance pressure.

Performance pressure refers to "a belief that current performance is inadequate for achieving a desired goal, and a negative affective response linked to the attitude and associated belief" (Eisenberger and Aselage, 2009, p. 96). It also refers to the urgency to achieve high performance levels because performance outcomes are tied to substantial consequences [START_REF] Mitchell | Cheating under pressure: a self-protection model of workplace cheating behavior[END_REF]. Research on performance pressure has revealed a contradictory set of consequences in that performance pressure seems to positively effect motivation and functional work behavior [START_REF] Eisenberger | Incremental effects of reward on experienced performance pressure: positive outcomes for intrinsic interest and creativity[END_REF][START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF] but at the expense of increased stress and unethical behavior [START_REF] Jensen | Predicting retail shrink from performance pressure, ethical leader behavior, and store-level incivility[END_REF]. Challenge-hindrance model [START_REF] Cavanaugh | An empirical examination of self-reported work stress among US managers[END_REF] has categorized stressors (i.e. antecedents of stress) into two categories: challenge stressors and hindrance stressors. The former refers to stressors that yield positive outcomes and gains for individuals, while the latter refers to stressors that do not yield positive outcomes or gain for the individuals [START_REF] Cavanaugh | Challenge and hindrance related stress among U.S. managers[END_REF]. Furthermore, challenge-hindrance model considered both types of stressors as priori, assuming that most people appraise stressors in the same way. However, [START_REF] Lepine | A meta-analytic test of the challenge stressorhindrance stressor framework: an explanation for inconsistent relationships among stressors and performance[END_REF] and [START_REF] Webster | Extending the challenge-hindrance model of occupational stress: the role of appraisal[END_REF] contended that the difference between the relationship of challenge and hindrance stressors with employee job-related outcomes depends upon how individuals appraise these stressors. Accordingly, [START_REF] Lazarus | Stress, Appraisal, and Coping[END_REF] in their cognitive theory of stress argued that how individuals appraise a stressor can provoke different coping processes. When a stressor is appraised as a challenge, it creates an internal focus on the potential opportunities from the situation, whereas a stressor appraised as a threat creates an internal focus on the potential harm or strain associated with addressing the situation. [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF], in extending cognitive theory of stress, theorized that how individuals appraise performance pressure can elicits both functional and dysfunctional behavior. More specifically, they suggested that performance pressure is a unique source of work stress and is appraised by the employees either as a challenge or threat, which, in turn, determines whether the pressure will result in more functional vs dysfunctional behaviors.

Yet, while evidence indicates that performance pressure affects work engagement, less is known about why employees may be more or less inclined to respond to the pressure functionally. Variation in how performance pressure is appraised may explain why such positive or negative behaviors emerge [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF]. According to transactional theory of stress [START_REF] Lazarus | Psychological Stress and the Coping Process[END_REF], stress reactions or processes are influenced by individuals' certain stable traits because some traits alter how individuals cognitively process information about stressors. Building on Lazarus' (1966) theory of stress with the tenets of Mitchell et al.'s (2019) theory, and responding to the call by [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF], we examine the moderating role of emotional stability (i.e. individual capability to adequately cope with negative emotions, such as anxiety, stress and anger; [START_REF] Alessandri | Job burnout: the contribution of emotional stability and emotional self efficacy beliefs[END_REF] on the relationship between performance pressure and work engagement. Unlike other personality traits (e.g. conscientiousness, extraversion), emotional stability is not only more closely associated with job-related aspects of individual behavior [START_REF] Oprea | Personality and boredom at work: the mediating role of job crafting[END_REF] but also has stronger ties with individuals' emotional and affective states, such as stress [START_REF] Alessandri | Job burnout: the contribution of emotional stability and emotional self efficacy beliefs[END_REF], exhaustion [START_REF] Liu | Emotional stability and citizenship fatigue: the role of emotional exhaustion and job stressors[END_REF] and subjective wellbeing [START_REF] Sobol-Kwapinska | Calm down-it's only neuroticism. Time perspectives as moderators and mediators of the relationship between neuroticism and well-being[END_REF]. Given that performance pressure may lead to emotion suppression instead of dealing with emotions [START_REF] Ness | Situational influences on ethical sense making: performance pressure, interpersonal conflict, and the recipient of consequences[END_REF], we argue that emotional stability may be more relevant in studying performance pressure and work engagement relationship.

Accordingly, our study contributes to the existing literature in several ways. First, it helps broaden the existing knowledge on the double-edged nature of performance pressure and is the first study to empirically examine work engagement in response to performance pressure via both threat and challenge appraisals and one of the few attempts to examine the role of coping strategy while dealing with performance pressure. Second, we contribute to the work engagement literature by examining how a single stressor can motivate different reactions, ultimately influencing employees' work engagement. [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF] argued that performance pressure is a unique and dynamic work stressor, appraised as either a threat or challenge, which, in turn leads to both positive and negative reactions. However, they only examined the effects of performance pressure on engagement through challenge appraisal ("an appraisal in which the perception of danger does not exceeds the perception of abilities or resources to cope with the stressor"; Tomaka et al., 1993, p. 248), whereas the question of whether threat appraisal ("an appraisal in which the perception of danger exceeds the perception of abilities or resources to cope with the stressor"; Tomaka et al., 1993, p. 248) influences employees' work engagement is still unanswered. We, therefore, extend the previous research and fulfill a research gap by examining the effects of performance pressure on work engagement through both threat and challenge appraisals.

Third, the present study adds to existing literature by examining the personality factor of emotional stability to understand its disparate moderating role on the effects of two types of appraisals, i.e. threat and challenge, on work engagement. Only few studies in the existing literature have examined the moderating factors of the relationship between performance pressure and its outcomes (e.g. [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF][START_REF] Zhang | Exploring the effects of job autonomy on engagement and creativity: the moderating role of performance pressure and learning goal orientation[END_REF]. In a recent study, [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF] found positive moderating role of trait resilience on performance pressure and its outcomes but called for further research to explore other intervening mechanisms in that relationships. Thus, in response to the appeal by [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF] to explore the moderating role of different personality traits, specifically the role of emotional stability on the stress process triggered by performance pressure, the present study provides insight into the mechanisms that might explain why and when performance pressure affects employees' stress appraisals and, in turn, their subsequent work engagement. Figure 1 depicts our hypothesized model.

Theoretical background and hypotheses development

Performance pressure, threat appraisal and work engagement Performance pressure is a subjective experience of "any factor or combination of factors that increase the importance of performing well" (Baumeister, 1984, p. 610). Rewards, punishments and competition in the workplace can produce the perception that meeting goals and achieving high levels of performance is highly important [START_REF] Prouska | Rewarding employees in turbulent economies for improved organisational performance: exploring SMEs in the South-Eastern European region[END_REF], which is also referred to as performance pressure [START_REF] Zhang | Exploring the effects of job autonomy on engagement and creativity: the moderating role of performance pressure and learning goal orientation[END_REF]. According to [START_REF] Gardner | Performance pressure as a double-edged sword: enhancing team motivation but undermining the use of team knowledge[END_REF], performance pressure is an external force imposed on employees to deliver a superior outcome and high levels of performance. The application of performance pressure is based on the belief that striving for high levels of performance is needed, which, in turn will lead to significant consequences [START_REF] Mitchell | Cheating under pressure: a self-protection model of workplace cheating behavior[END_REF][START_REF] Tan | Workplace gossip prevalence on job performance: the mediating role of performance pressure[END_REF]. Performance pressure is different from other types of work stressors, such as pressures to speed up the completion of tasks or due to heavy workloads [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF]. Performance pressure is defined as the urgent demands or constraints placed on an individual to respond in a certain way [START_REF] Baucus | Pressure, opportunity and predisposition: a multivariate model of corporate illegality[END_REF]. More specifically, performance pressure can be defined as creating the urgency for employees to achieve high performance levels to attain desirable consequences and to avoid negative consequences [START_REF] Mitchell | Cheating under pressure: a self-protection model of workplace cheating behavior[END_REF].

Research on performance pressure has found that it is a unique and dynamic work stressor which acts as a double-edged sword in that it can motivate employees to perform well [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF], be more ethical [START_REF] Ness | Situational influences on ethical sense making: performance pressure, interpersonal conflict, and the recipient of consequences[END_REF] and creative [START_REF] Zhang | Exploring the effects of job autonomy on engagement and creativity: the moderating role of performance pressure and learning goal orientation[END_REF], while also increasing stress [START_REF] Mitchell | Cheating under pressure: a self-protection model of workplace cheating behavior[END_REF] and deviant behavior [START_REF] Jensen | Predicting retail shrink from performance pressure, ethical leader behavior, and store-level incivility[END_REF]. [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF] theorized that performance pressure elicits both positive and negative workrelated behaviors which depends on the extent to which individuals appraise the performance pressure as a challenge or a threat. Challenge appraisal is defined as "an appraisal in which the perception of danger does not exceeds the perception of abilities or resources to cope with the stressor" (Tomaka et al., 1993, p. 248). In contrast, threat appraisal refers to "an appraisal in which the perception of danger exceeds the perception of abilities or resources to cope with the stressor" (Tomaka et al., 1993, p. 248). Individuals with challenge appraisals perceive the possibility of gain from meeting the assigned goals and are more likely to display positive behaviors [START_REF] Ohly | Work characteristics, challenge appraisal, creativity, and proactive behavior: a multi-level study[END_REF]. Whereas, individuals with threat appraisals perceive the potential for loss and possibility of failing to perform, thereby facilitating dysfunctional behaviors [START_REF] Fugate | Managing employee withdrawal during organizational change: the role of threat appraisal[END_REF]. For example, students who think they are well-prepared are more likely to feel challenged, energized and eager to appear in the examination, whereas students who perceive themselves as unprepared are more likely to feel threatened and anxious to perform.

Performance pressure appraised as a threat can be detrimental [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF]. Employees' experiencing high demands for higher performance may perceive their efforts ineffective at meeting performance goals [START_REF] Zhang | Exploring the effects of job autonomy on engagement and creativity: the moderating role of performance pressure and learning goal orientation[END_REF]. Employees appraising job demands (e.g. work pressure, performance pressure) as threatening may feel stress [START_REF] Casper | Feeling exhausted or vigorous in anticipation of high workload? The role of worry and planning during the evening[END_REF] and may concentrate on the difficulties of raising performance and the adverse consequences that will likely result if performance demands are not met [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF]. These perceptions could also lead employees to experience negative outcomes such as job dissatisfaction [START_REF] Quratulain | How does employees' public service motivation get affected? A conditional process analysis of the effects of person-job fit and work pressure[END_REF], deviant behavior [START_REF] Jensen | Predicting retail shrink from performance pressure, ethical leader behavior, and store-level incivility[END_REF][START_REF] Soomro | Antecedents of workplace deviance: role of job insecurity, work stress, and ethical work climate[END_REF] and low job involvement [START_REF] Sonnentag | Psychological detachment from work during off-job time: the role of job stressors, job involvement, and recovery-related self-efficacy[END_REF] if performance is not raised. However, we lack empirical evidence on whether performance pressure impacts employee work engagement through threat appraisal. Based on Mitchell et al.'s (2019) theorization, performance pressure appraised as a threat depletes employees' self-resources (i.e. energy) which then leads to dysfunctional behavior. This depletion in self-resources may also lead employees to lower levels of work engagement [START_REF] Xanthopoulou | Reciprocal relationships between job resources, personal resources, and work engagement[END_REF]. Thus, on the basis of above theoretical principles and research findings, it can be presumed that threat appraisal emanating from performance pressure has a negative influence on employees' work engagement.

H1. Performance pressure has a negative indirect effect on work engagement through threat appraisal.

Performance pressure, challenge appraisal and work engagement Performance pressure can also be appraised as a challenge [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF]. Demands for high level of performance can create a foundation for growth and development (Ab Wahab and Tatoglu, 2020). [START_REF] Ko | Overtime work as the antecedent of employee satisfaction, firm productivity, and innovation[END_REF] argued that high demands for performance can promote performance, especially if workers perceived it as an opportunity for their career progression, growth or development. Moreover, employees may also view performance pressure as an opportunity to restructure their capabilities and focus on achieving the goals successfully [START_REF] Gardner | Performance pressure as a double-edged sword: enhancing team motivation but undermining the use of team knowledge[END_REF]. In a meta-analysis, [START_REF] Lepine | A meta-analytic test of the challenge stressorhindrance stressor framework: an explanation for inconsistent relationships among stressors and performance[END_REF] found a positive relation between challenge appraisal and performance and they argued that challenge appraisal facilitates performance through the direction, level and persistence of effort toward assigned tasks. They also argued that the appraisal of a situation as challenging should lead to the belief that if certain goals are met by exercising effort, valued outcomes will occur. Several studies clearly indicate that challenge appraisal is associated with various positive workrelated outcomes such as, creativity, performance, task proficiency and indicators of employee growth and development [START_REF] Ko | Overtime work as the antecedent of employee satisfaction, firm productivity, and innovation[END_REF][START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF][START_REF] Ohly | Work characteristics, challenge appraisal, creativity, and proactive behavior: a multi-level study[END_REF][START_REF] Prem | Thriving on challenge stressors? Exploring time pressure and learning demands as antecedents of thriving at work[END_REF].

Existing research suggests that employees can cope well with a certain level of work pressure, which is expected to lead to more effort and thus increased work engagement (Leppinkand P erez-Fuster, 2019;[START_REF] Petrou | Weekly job crafting and leisure crafting: implications for meaning-making and work engagement[END_REF]. [START_REF] Kronenwett | All's well that ends well!? Moderating effects of goal progress on the relation between challenge and hindrance appraisal and well-being[END_REF] argued that high work demand (in our case: high performance pressure) leads to an increase in effort because people try to meet their goals. This argument leads us to expect increased levels of work engagement when performance pressure is perceived as a challenge. According to Mitchel et al. (2019), employees who focus on attributes of performance pressure that are beneficial (i.e. challenge appraisal) fuel their internal self-resources (i.e. energy), which, in turn, enhances their engagement. Therefore, on the basis of Mitchel et al.'s (2019) theorization and research findings, it can be presumed that challenge appraisal emanating from performance pressure has a positive influence on employees' work engagement.

H2. Performance pressure has a positive indirect effect on work engagement through challenge appraisal.

Moderating role of emotional stability

The importance of personality traits for predicting work-related outcomes has been widely demonstrated [START_REF] Albrecht | Personality, self-efficacy and job resources and their associations with employee engagement, affective commitment and turnover intentions[END_REF][START_REF] Alessandri | Job burnout: the contribution of emotional stability and emotional self efficacy beliefs[END_REF]Tisuet al., 2020). Personality is often referred to as one's emotions, thoughts and behavioral patterns [START_REF] Kassin | Psychology[END_REF]. The Big five personality (also known as the Five-Factor Model) is frequently used to describe the structure of personality [START_REF] Oentoro | Perceived supervisory support and service recovery performance: the moderating role of personality traits[END_REF] and has been used in different countries, in various organizational settings and across rating sources. Although big five personality traits were derived since 1936 from the earlier trait research of Allport and Olbert (1936) and [START_REF] Cattell | Personality and Motivation Structure and Measurement[END_REF], [START_REF] Tupes | Recurrent personality factors based on trait ratings[END_REF] were the first to discover the Big Five-factor in 1961.

The big five consists of five dimensions of personality, namely, conscientiousness, agreeableness, neuroticism, extraversion and openness to new experience. Emotional stability, the opposite of neuroticism, is one of the Big Five personality dimensions. Emotional stability, defined as an individual's capability to adequately cope with negative emotions, such as anxiety, stress and anger [START_REF] Alessandri | Job burnout: the contribution of emotional stability and emotional self efficacy beliefs[END_REF], has been considered as the basis of human personality. After conscientiousness, it is considered to be the most important personality trait in work contexts [START_REF] Barrick | Select on conscientiousness and emotional stability[END_REF] and a key individual characteristic that is negatively associated with stress-related variables, such as job burnout (Fornes-Vives et al., 2019), emotional exhaustion [START_REF] Sosnowska | Relating neuroticism to emotional exhaustion: a dynamic approach to personality[END_REF], anxiety [START_REF] Chen | The impact of neuroticism on symptoms of anxiety and depression in elderly adults: the mediating role of rumination[END_REF] and anger [START_REF] Rogers | Workplace intrusions and employee strain: the interactive effects of extraversion and emotional stability[END_REF].

According to [START_REF] Lazarus | Psychological Stress and the Coping Process[END_REF] transactional theory of stress, certain personality traits influence the stress process because they have the tendency to alter how individuals process information about stressors. Based on the arguments of [START_REF] Lazarus | Psychological Stress and the Coping Process[END_REF], Mitchel et al. (2019) theorized that stress experience caused by the demand for high performance (i.e. performance pressure) can be influenced by certain personality traits in a way that could alter the way the pressure is appraised, which, in turn, could affect the performance pressure experience. Prior research on work-related stressors have identified emotional stability as a particular impactful individual trait for the stress process [START_REF] Alessandri | Job burnout: the contribution of emotional stability and emotional self efficacy beliefs[END_REF]. Emotional stability captures individuals' predisposition to experience negative affect [START_REF] Li | Emotional stability: a new construct and its implications for individual behavior in organizations[END_REF] and helps individuals to stay calm under novel and stressful situations [START_REF] Rogers | Workplace intrusions and employee strain: the interactive effects of extraversion and emotional stability[END_REF]. We focus on emotional stability as a potential moderator between performance pressure and stress appraisals (i.e. challenge or threat appraisals) because emotional stability captures the tendency for individuals to effectively adapt and cope with stress, loss, hardship or adversity [START_REF] Alessandri | Job burnout: the contribution of emotional stability and emotional self efficacy beliefs[END_REF][START_REF] David | Emotions running high: examining the effects of supervisor and subordinate emotional stability on emotional exhaustion[END_REF]. More important, accumulated research has established that emotional stability plays the most central role in shaping individuals' reactivity to stressors in terms of the effectiveness of coping strategies [START_REF] Li | Intra-individual variability in job complexity over time: examining the effect of job complexity trajectory on employee job strain: job Complexity Change and Job Strain[END_REF] and navigating stress experiences positively rather than focusing on negative aspects of stressors [START_REF] Kaiser | Emotional stability and goal-related stress[END_REF].

Accordingly, we suggest that emotional stability will moderate the effects of performance pressure on stress appraisals (i.e. threat and challenge appraisals). We further suggest that low emotional stability would decrease employee ability to ignore negative aspects of performance pressure, such as raising performance standards or meeting high performance demands, thus influencing employees to be more likely to appraise the performance pressure as threatening. In contrast, high emotional stability would enable greater employee ability to focus on the positive aspects of performance pressure (e.g. opportunities for growth and development or potential rewards against meeting the performance demands) and will help them navigate negative stress experience positively, thus making employees more likely to appraise the performance pressure as challenging. We thus hypothesize the following:

H3a. The positive relationship between performance pressure and threat appraisal will be stronger when emotional stability is lower rather than higher.

H3b. The positive relationship between performance pressure and challenge appraisal will be weaker when emotional stability is lower rather than higher.

Moreover, emotionally stability can increase employees' ability to remain stable and balanced and thus may optimize their personal resources [START_REF] Albrecht | Personality, self-efficacy and job resources and their associations with employee engagement, affective commitment and turnover intentions[END_REF] to secure themselves from hectic situations and its costs; furthermore, such personal resources act as a proximal antecedents of work engagement [START_REF] Albrecht | Personality, self-efficacy and job resources and their associations with employee engagement, affective commitment and turnover intentions[END_REF]. Individuals with a higher level of emotional stability usually invest their energy to obtain more experience and increase work engagement [START_REF] Janssens | Do personality traits determine work engagement? Results from a Belgian study[END_REF]. By pre-empting the negative consequences of work pressure that may hinder performance, emotional stability help employees more effectively handle stressful situations [START_REF] David | Emotions running high: examining the effects of supervisor and subordinate emotional stability on emotional exhaustion[END_REF][START_REF] Smith | Does perfectionism predict depression, anxiety, stress, and life satisfaction after controlling for neuroticism?[END_REF] and thus enhance work engagement [START_REF] Janssens | Do personality traits determine work engagement? Results from a Belgian study[END_REF]. Therefore, we suggest that emotional stability switches the indirect effects of performance pressure between the appraisal and challenge pathways. That is, individuals with higher levels of emotional stability will perceive the performance pressure as a challenge rather than a threat because emotional stability trait helps individuals to stay calm under stressful situations [START_REF] Alessandri | Job burnout: the contribution of emotional stability and emotional self efficacy beliefs[END_REF], which would ultimately enhance their state of engagement (i.e. work engagement). Conversely, employees with lower levels of emotional stability will perceive the performance pressure as a threat rather than a challenge because they are often nervous, have low self-esteem and are unable to handle the stress effectively [START_REF] Jankovic | Workplace violence, post-traumatic stress disorder symptoms, and personality[END_REF], which will ultimately affect their work engagement. Thus, we hypothesize following:

H4. The indirect effect of performance pressure on work engagement through (a) threat appraisal and (b) challenge appraisal will be stronger when emotional stability is higher.

Method

Participants and procedure Data were collected from white-collar employees working in different sectors in France, including those in the transport, banking, tourism, consulting and telecom sectors. These five sectors were targeted because they are the most common sectors in France. One of the authors personally contacted company managers in these sectors. Fifteen managers showed interest in our research project and invited employees working in their companies to join the research. We first informed the participants about the general aim of the study, how it would be carried out (i.e. in three waves) and provided assurances that their responses would be kept confidential. Due to the nature of our study (i.e. three-wave research design), we collected participants' email addresses and told them that they would receive the survey form by email.

In addition, following the principles of snowball sampling [START_REF] Biernacki | Snowball sampling: problems and techniques of chain referral sampling[END_REF], we asked the interested participants to recommend other participants. In addition, we sent invitations to French employees on professional networking sites such as LinkedIn and Viadeo. The inclusion criterion for the final sample was having a part-or full-time job in one of the five selected sectors.

To reduce common method bias [START_REF] Podsakoff | Sources of method bias in social science research and recommendations on how to control it[END_REF], the data collection occurred in three waves, separated by two months each. According to Luu (2019), a two-month time lag is sufficient to avoid the biasing effects of occasional factors (e.g. the pressure one faces at the time of survey completion). [START_REF] Matthews | A longitudinal examination of role overload and work-family conflict: the mediating role of interdomain transitions: interdomain transitions[END_REF] also suggested that a minimum of onemonth time lag would be sufficient time for stressor-strain relationships to unfold. In the first phase, participants completed questionnaire regarding demographic variables, performance pressure and emotional stability. In the second phase, the survey measured mediating variables of threat appraisal and challenge appraisal. In the third phase, the participants were asked to complete work engagement scale. Initially, 625 participants completed the first survey. In the second wave, 353 respondents completed the survey and then 247 surveys were received in the third wave (overall response rate 5 39%).

The final sample included 138 women (56%) and 109 men (44%) employees with ages ranging from 20 to 54 (M 5 30.8 years, SD 5 6.8). On average, respondents had a mean tenure of 5.7 years (SD 5 2.17). The majority of the participants were employed in the private sector (68%) and represented each of the five sectors, i.e. banking (30%), consulting (28%), telecom (18%), transportation (13%) and tourism (11%). Of the respondents, 90.7% had a bachelor's degree and 36.8% worked in the managerial positions.

Measures

The survey was administered both in English and French since these languages are spoken by a vast majority of French population and are commonly used in organizational contexts [START_REF] Kundi | Employee psychological well-being and job performance: exploring mediating and moderating mechanisms[END_REF]. We followed the back-translation procedure recommended by [START_REF] Brislin | Translation and content analysis of oral and written materials[END_REF] to translate the scales from English to French.

Performance pressure. Performance pressure was measured with a four-item scale developed by [START_REF] Mitchell | Cheating under pressure: a self-protection model of workplace cheating behavior[END_REF]. Sample items are "I feel tremendous pressure to produce results" and "I feel that if I do not produce at high levels, my job will be at risk" (α 5 0.82). Items were rated on a 7-point scale (1 5 strongly disagree and 7 5 strongly agree).

Threat appraisal. We measured threat appraisal with three items borrowed from Drach-Zahavy and Erez (2002). Sample items are "The demands of my work hinder my abilities "and" I'm worried that the task might reveal my weaknesses" (α 5 0.97). Items were rated on a 7-point scale (1 5 strongly disagree and 7 5 strongly agree).

Challenge appraisal. Challenge appraisal was measured using three items from Drach-Zahavy and Erez (2002). Sample items are "The task seems like a challenge to me" and "The task provides opportunities to exercise reasoning skills" (α 5 0.91). Items were rated on a 7-point scale (1 5 strongly disagree and 7 5 strongly agree).

Work engagement. Work engagement was measured with three items borrowed from the Ultrecht Work Engagement Scale (UWES; [START_REF] Schaufeli | The measurement of engagement and burnout: a two sample confirmatory factor analytic approach[END_REF], also used by [START_REF] Wang | The daily motivators: positive work events, psychological needs satisfaction, and work engagement[END_REF]. According to [START_REF] Schaufeli | The measurement of engagement and burnout: a two sample confirmatory factor analytic approach[END_REF], work engagement has three dimensions, i.e. vigor, absorption and dedication, which tend to correlate significantly with each other and usually load together. The three items for work engagement are "I feel bursting with energy at work", "I am enthusiastic about my work" and "I am immersed in my work" (α 5 0.86). Items were rated on a 7-point scale (1 5 not at all and 7 5 extremely).

Emotional stability. Emotional stability was measured with a ten-item negative affectivity scale [START_REF] Watson | Development and validation of brief measures of positive and negative affect: the PANAS scales[END_REF]. Negative affectivity is characterized by experiencing negative emotions [START_REF] Watson | Negative affectivity: the disposition to experience aversive emotional states[END_REF]. All the items of negative affectivity scale were reversed coded to measure emotional stability since these two constructs are often used interchangeably (see [START_REF] Wihler | Conscientiousness, extraversion, and field sales performance: combining narrow personality, social skill, emotional stability, and nonlinearity[END_REF]. The instructions read "To what extent do you feel this way generally." A sample item includes "nervous". Items were rated on a 7-point scale (1 5 not at all and 7 5 extremely). Cronbach's α 5 0.85.

Control variables.

In our analysis, we controlled for age, gender and organizational tenure as these factors have been found to influence employee work engagement (e.g. [START_REF] Bakker | The crossover of burnout and work engagement among working couples[END_REF][START_REF] Matsuo | Effect of learning goal orientation on work engagement through job crafting: a moderated mediation approach[END_REF].

Results

Descriptive statistics

Table 1 presents the means, standard deviations and bivariate correlations among the study variables.

Measurement assessment

Prior to hypotheses testing, we used confirmatory factor analysis (CFA) to examine the distinctiveness of the five variables included in this study, namely, performance pressure, threat appraisal, challenge appraisal, emotional stability and work engagement. Comparing the baseline model against several alternative models revealed that the five-factor model was statistically significant above and beyond alternate models (χ 2 5 247.931, df 5 123, CFI 5 0.96, TLI 5 0.95, RMSEA 5 0.06, and SRMR 5 0.05; see Table 2). These results provide empirical support for the distinctive nature of our study variables and meet the standard cutoff values proposed by [START_REF] Hu | Cutoff criteria for fit indexes in covariance structure analysis: conventional criteria versus new alternatives[END_REF]. To ensure the validity of our measures, we first examined the convergent validity through: (1) construct reliability (i.e. composite reliability) and (2) average variance extracted (AVE). We found composite reliability coefficients higher than the threshold value of 0.7, whereas AVE scores higher than the threshold value of 0.5 (see Table 1; [START_REF] Fornell | Structural equation models with unobservable variables and measurement error: algebra and statistics[END_REF], supporting the convergent validity of our constructs. We also estimated discriminant validity by comparing the AVE of each construct with the average shared variance (ASV), i.e. mean of the squared correlations among constructs [START_REF] Hair | Multivariate Data Analysis: A Global Perspective[END_REF]. As expected, all the values of AVE were higher than the ASV constructs, thereby supporting discriminant validity (see Table 1).

Finally, we tested for the presence of a common method effect since we collected data from the same source (i.e. employees).We ran a CFA version of Harman's single-factor test (cf. Kundi et al., 2020a, b). The results showed that the single-factor model produced an extremely poor fit to the data (χ 2 5 1789.28, df 5 133, CFI 5 0.43, TLI 5 0.34, RMSEA 5 0.23, SRMR 5 0.24). In addition, we conducted CFA marker variable technique [START_REF] Lindell | Accounting for common method variance in cross-sectional research designs[END_REF][START_REF] Williams | Method variance and marker variables: a review and comprehensive CFA marker technique[END_REF] to assess CMV. We used De Witte's (2000) four-item job insecurity scale (e.g. "I feel insecure about the future of my job") as a marker variable. We ran a model in which the indicators of the study's substantive variables were specified to load onto the latent marker variable (χ 2 5 296.797, df 5 171) and compared it to a model in which

Table 1.

Correlations and descriptive analysis they did not load onto the marker variable (χ 2 5 243.699, df 5 122). The chi-square difference test between two models was nonsignificant (Δχ 2 = 53.098, Δdf 5 49, p 5 0.32), suggesting that CMV is not a pervasive problem.

Hypotheses testing

The hypotheses pertaining to mediation were tested using a structural model (see Figure 2), which had an acceptable goodness of fit, i.e. χ 2 (58) 5 114.649, CFI 5 0.98, TLI 5 0.97, RMSEA 5 0.06, and SRMR 5 0.04. Hypotheses pertaining to moderation and moderated mediation were tested in SPSS (25th edition) using PROCESS model 7 [START_REF] Hayes | Introduction to Mediation, Moderation, and Conditional Process Analysis: A Regression-Based Approach[END_REF]; see Table 3). Studies that theorized and tested moderated mediation research models increasingly relied on this approach (e.g. De [START_REF] De Clercq | Perceived organizational injustice and counterproductive work behaviours: mediated by organizational identification, moderated by discretionary human resource practices[END_REF][START_REF] Matsuo | Effect of learning goal orientation on work engagement through job crafting: a moderated mediation approach[END_REF].

Hypothesis 1 suggested that performance pressure has a negative indirect effect on work engagement via threat appraisal. As shown in Figure 2, the indirect effect of performance pressure on work engagement, through threat appraisal, was negative and significant (β 5 À0.042, 95% CI 5 À0.103; À0.001), supporting Hypothesis 1. Similarly, Hypothesis 2 suggested that performance pressure has a positive indirect effect on work engagement via challenge appraisal. As shown in Figure 2, the indirect effect of performance pressure on work engagement, through challenge appraisal, was positive and significant (β 5 0.128, 95% CI 5 0.128; 0.489), supporting Hypothesis 2. Hypothesis 3a suggested that the positive effect of performance pressure on threat appraisal will be stronger when emotional stability was lower than higher. As can be seen in Table 3, the interaction term between performance pressure and emotional stability negatively influenced threat appraisal (β 5 À0.42, p < 0.05). In order to interpret the interaction effects, the simple slopes for the significant interaction effects (i.e. for the low and high values of the moderating variables) were plotted (see Figure 3) and assessed for significance. Simple slope test results revealed that the linkage between performance pressure and threat appraisal was significant when emotional stability was low (À1 SD, β 5 0.76, p < 0.001) rather than high (þ1 SD, β 5 0.18, ns). Hypothesis 3a, therefore, was fully supported. Hypothesis 3b suggested that the positive effect of performance pressure on challenge appraisal will be stronger when emotional stability was higher than lower. As can be seen in Table 3, the interaction term between performance pressure and emotional stability positively influenced challenge appraisal (β 5 0.31, p < 0.01). The plot is presented in Figure 4. As expected, performance pressure was positively related to challenge appraisal when emotional stability was high (þ1SD, β 5 0.63, p < 0.001) rather than low (À1SD, β 5 0.19, ns). Hence, Hypothesis 3b was fully supported.

Hypothesis 4 suggested that the indirect effects of performance pressure on work engagement through (1) threat appraisal and (2) challenge appraisal will be stronger when emotional stability is higher than lower. The results showed that the indirect effect of performance pressure on work engagement through threat appraisal was stronger when emotional stability was higher (β 5 À0.028, 95% CI 5 À0.0816; 0.0303) rather than lower (β 5 À0.117, 95% CI 5 À0.2410; À0.0354). The index of moderated mediation was significant (Index 5 0.063, 95% CI 5 0.0029; 0.1711). Similarly, the indirect effect of performance pressure on work engagement through challenge appraisal was stronger when emotional stability was higher (β 5 0.20, 95% CI 5 0.1015; 0.3258) rather than lower (β 5 0.06, 95% CI 5 À0.0286; 0.1629). The index of moderated mediation was significant (Index 5 0.10, 95% CI 5 0.0249; 0.1935). Overall, these results supported Hypothesis 4a and 4b.

Discussion

The purpose of this research was to uncover the relationship between performance pressure and employee work engagement. Integrating Lazare's theory of stress (1966) with the tenets of Mitchell et al.'s (2019) theorization, we hypothesized that performance pressure would yield both positive and negative consequences on employee work engagement. We found that performance pressure experience has both positive and negative outcomes. When performance pressure is perceived as a threat, it creates a taxing experience that lowers employee work engagement. In contrast, when the performance pressure is perceived as a challenge or opportunity, it promotes employee work engagement. Furthermore, we found emotional stability as an influential personality trait in this stress experience because it creates a lens through which employee filter the performance pressure. We found that employees with low emotional stability are more likely to appraise the performance pressure as threatening, thereby diminishing their work engagement, whereas employees with high The moderating role of emotional stability on performance pressurechallenge appraisal relationship levels of emotional stability are more likely to appraise the performance pressure as challenging, thereby enhancing their work engagement.

Theoretical implications

Our study has several theoretical implications. First, our study contributes to and advances the emerging literature on performance pressure, which has previously produced mixed results on outcomes of such pressure. Some research demonstrated that performance pressure enhances functional behavior (e.g. [START_REF] Tan | Workplace gossip prevalence on job performance: the mediating role of performance pressure[END_REF][START_REF] Zhang | Exploring the effects of job autonomy on engagement and creativity: the moderating role of performance pressure and learning goal orientation[END_REF], while others found performance pressure producing dysfunctional behavior (e.g. [START_REF] Byun | The trickle-down effect of empowering leadership: a boundary condition of performance pressure[END_REF][START_REF] Jensen | Predicting retail shrink from performance pressure, ethical leader behavior, and store-level incivility[END_REF], and some even reported both positive and negative outcomes [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF]. Based on tenets of Mitchell et al.'s (2019) theory, our primary contribution lies in investigating the paradoxical consequences of performance pressure on employee work engagement. Although it has been argued that performance pressure is appraised as either threat or challenge [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF], which in turn may leads to both positive and negative consequences [START_REF] Baethge | A matter of time? Challenging and hindering effects of time pressure on work engagement[END_REF], research explicitly investigating the consequences of such pressure on employee work engagement has largely been absent from the extant literature. Our results showed that performance pressure has both positive and negative consequences. Surprisingly, we found a positive indirect relationship between performance pressure and employee work engagement when the pressure was appraised as a challenge and an indirect negative relationship between performance pressure and work engagement when the pressure was appraised as a threat. The findings support Mitchell et al.'s (2019) theory which implies that performance pressure is a double-edge sword, either appraised as a threat or as a challenge. If appraised as a challenge, it may have positive outcomes, and if appraised as a threat, it may have negative outcomes. This finding presents the study's first theoretical contribution to the work engagement literature by providing evidence of the existence paradoxical outcomes between perceived performance pressure and work engagement. Namely, to date, only one study has investigated the relationship between performance pressure and engagement but only through the path of challenge appraisal [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF]. Second, we contribute to the personality literature by examining the moderating role of emotional stability targeted at the two types of appraisals, i.e. threat and challenge appraisals. We responded to Mitchell et al.'s (2019) call to examine the moderating role of different personality traits, especially emotional stability, on the stress process triggered by the performance pressure. We found that emotional stability strengthens the effects of performance pressure on challenge appraisal, whereas emotional stability mitigates the effects of performance pressure on threat appraisal. These results suggest that performance pressure benefits can be mixed for organizations unless employees have high emotional stability because emotional stability offers an optimistic lens through which employees appraise the pressure as beneficial and challenging rather than harmful or threatening. [START_REF] Rogers | Workplace intrusions and employee strain: the interactive effects of extraversion and emotional stability[END_REF] argued that emotional stability is characterized by stress tolerance and decreased negative affect. They also argued that emotional stability serves as a personal resource, such that emotionally stable employees may perceive fewer work pressures and experience less stress as a result of such pressures. Previous studies have found that employees scoring high on emotional stability are more likely to engage in response to stressors [START_REF] Alessandri | Job burnout: the contribution of emotional stability and emotional self efficacy beliefs[END_REF][START_REF] David | Emotions running high: examining the effects of supervisor and subordinate emotional stability on emotional exhaustion[END_REF][START_REF] Fornes-Vives | Longitudinal study predicting burnout in Spanish nurses: the role of neuroticism and emotional coping[END_REF][START_REF] Sosnowska | Relating neuroticism to emotional exhaustion: a dynamic approach to personality[END_REF].

Moreover, we contribute to the work engagement literature by examining how a single stressor (i.e. performance pressure) can motivate different reactions (i.e. threat and challenge appraisals), ultimately influencing employees' work engagement. We draw on [START_REF] Lazarus | Psychological Stress and the Coping Process[END_REF] theory of stress with the tenets of Mitchell et al.'s (2019) theory to examine the moderating role of emotional stability on the performance pressure and work engagement relationship. Our results indicated that employees with high emotional stability are more likely to appraise the pressure as beneficial and challenging rather than harmful and threatening, which promotes their work engagement. Employees with high emotional stability are more likely to experience positive emotions [START_REF] Li | Emotional stability: a new construct and its implications for individual behavior in organizations[END_REF] rather than a range of negative emotions such as depression, anxiety and stress than those with low emotional stability [START_REF] Alessandri | Job burnout: the contribution of emotional stability and emotional self efficacy beliefs[END_REF][START_REF] David | Emotions running high: examining the effects of supervisor and subordinate emotional stability on emotional exhaustion[END_REF]. In addition, employees with high emotional stability have strong desires to attain success and achieve high performance [START_REF] Wihler | Conscientiousness, extraversion, and field sales performance: combining narrow personality, social skill, emotional stability, and nonlinearity[END_REF] and, thus, develop a stronger sense of obligation to put efforts toward job [START_REF] Kleine | Thriving at work: a meta-analysis[END_REF]. As such, we demonstrated that employee stability could be both functional (when high) and dysfunctional (when low) in perceiving performance pressure. In doing so, we enrich the knowledge of the effects of performance pressure and emotional stability by identifying individuals who are more likely to be influenced by performance pressure.

Practical implications

Performance pressure at work is increasing [START_REF] Jensen | Predicting retail shrink from performance pressure, ethical leader behavior, and store-level incivility[END_REF], and there are no indicators of a trend in the opposite direction; therefore, managers are confronted with the challenge of how to motivate an employee to perform well, one of the most desirable behaviors in today's work environment [START_REF] Prouska | Rewarding employees in turbulent economies for improved organisational performance: exploring SMEs in the South-Eastern European region[END_REF]. Our study investigates this challenge, and the results offer some practical implications. First, findings suggest that performance pressure can be a double-edged sword, motivating both positive and negative outcomes. Employees appraising the performance pressure as a threat may be motivated toward dysfunctional behavior. However, employees appraising it as a challenge may increase functional behavior at work. Therefore, managers should be aware of how their employees appraise performance expectations. Managers should take care in how they communicate performance expectations to employees to diminish the likelihood that those expectations may be negatively appraised (i.e. threat appraisal). Instead, managers should be able to facilitate increased employee motivation by explaining the benefits and opportunities tied with meeting those expectations.

Second, our study proposed that performance pressure could be favorable to work engagement. Thus, if supervisors are interested in boosting employees' work engagement, they should identify how they appraise the pressure. If the pressure is appraised as a challenge, it may boost their energy [START_REF] Ohly | Work characteristics, challenge appraisal, creativity, and proactive behavior: a multi-level study[END_REF][START_REF] Prem | Thriving on challenge stressors? Exploring time pressure and learning demands as antecedents of thriving at work[END_REF] ultimately enhancing their work engagement. However, if the pressure is appraised as a threat, employees may lose hope and feel demotivated [START_REF] Mitchell | Cheating under pressure: a self-protection model of workplace cheating behavior[END_REF] ultimately lowering their work engagement. It is important to note that frequent and continuous high-performance pressure may lead to incivility and other negative consequences [START_REF] Mitchell | Can you handle the pressure? The effect of performance pressure on stress appraisals, self-regulation, and behavior[END_REF]. Thus, it is important that managers with higher performance expectations should provide employees with full support to stimulate their work engagement. Besides this, managers need to ensure that long-term exposure to high-performance pressure should be avoided [START_REF] Baethge | A matter of time? Challenging and hindering effects of time pressure on work engagement[END_REF].

Finally, our findings suggest that performance pressure may be both harmful and helpful; however, it depends on the person experiencing the performance pressure. We found that employees with high emotional stability paid attention to challenging aspects of performance pressure while seemingly ignoring threatening aspects of the pressure. They were found to have greater work engagement due to performance pressure. On the other hand, employees with low emotional stability were more likely to appraise performance pressure as threatening, ultimately lowering their work engagement. Therefore, organizations should use personality measures to assess important personality traits during hiring and screening processes because certain traits influence positive motivational states and behaviors [START_REF] Zeigler-Hill | Integrating motivation into current conceptualizations of personality[END_REF]. Moreover, managers could choose employees with high emotional stability for the tasks that require high work demand and are challenging in nature. Last but not least, interventions such as enhancing employees' levels of mindfulness, creating resourceful work environment (e.g. redesigning jobs and providing social support), and provision of training, counseling and mentoring can prove to be effective in enhancing employees' emotional stability [START_REF] Bakker | Job demands-resources theory: taking stock and looking forward[END_REF][START_REF] Bajaj | Emotional stability and self-esteem as mediators between mindfulness and happiness[END_REF].

Limitations and future research directions

There are several limitations to this study. First, all variables in our study were assessed with self-report scales which may raise concerns about common method bias [START_REF] Podsakoff | Sources of method bias in social science research and recommendations on how to control it[END_REF]. Yet, collecting sensitive behaviors from the focal source has been demonstrated by meta-analysis to be more accurate than reports from others [START_REF] Carpenter | Are supervisors and coworkers likely to witness employee counterproductive work behavior? An investigation of observability and self-observer convergence[END_REF]. We addressed the possibility of CMV in our surveys by (1) using three-wave data collection procedure, (2) conducting CFA marker variable analyses which suggested that common method bias was unlikely to be a problem and (3) included a moderator variable in our model which scholars have demonstrated cannot be inflated by CMV (e.g. [START_REF] Podsakoff | Sources of method bias in social science research and recommendations on how to control it[END_REF][START_REF] Siemsen | Common method bias in regression models with linear, quadratic, and interaction effects[END_REF]. We found significant interaction effects of emotional stability, and the indirect effect of performance pressure on work engagement (through threat and challenge appraisals) was also significant. Therefore, it is unlikely CMV presented a bias and, based on Podsakoff et al.'s (2012) arguments, if CMV were present, the interactions would have been deflated by CMV. However, future research should attempt to replicate our results by using alternative research designs, such as experimental or longitudinal studies, that strengthen assumptions of causality and mitigate common method bias.

Second limitation concerns generalizing our study's findings to other cultures and regions as the sample is exclusively from France. Future research may benefit from examining our model within other relevant contexts across a range of countries and cultures. Third, although we have involved age, gender and organizational tenure as the control variables, other factors may influence work engagement. For instance, previous research has shown that work engagement is highly determined by job resources [START_REF] Bakker | Job demands-resources theory: taking stock and looking forward[END_REF], which longitudinally show reciprocal relationships with personal resources and work engagement [START_REF] Xanthopoulou | Reciprocal relationships between job resources, personal resources, and work engagement[END_REF]. Thus, future research, when attempting to replicate our study's results, consider additional control variables.

Finally, our study has highlighted an important role of emotional stability on weakening the negative effects (i.e. threat appraisal) of performance pressure. Future research can explore the effect of other personality traits (e.g. promotion-focused, perfectionism and proactive personality) which may enhance or dull the salience of stressors. Future research might also explore the moderating role of contextual factors (e.g. instrumental, personal or supervisor support received at work) with respect to our model.

Conclusion

Our study has shown that performance pressure can have differential effects on employees' work engagement. Performance pressure appraised as a threat diminishes employees' work engagement, whereas performance pressure appraised as a challenge promotes employees' work engagement. Emotional stability influences the performance pressure stress experience such that higher emotional stability enhances employee ability to handle the pressure due to being more likely to view it as challenge, which heightens engagement behaviors at work. Finally, we want to add and emphasize that research on performance pressure has documented its health-impairing effects [START_REF] Mitchell | Cheating under pressure: a self-protection model of workplace cheating behavior[END_REF]. Because previous evidence indicates that stress arising from high work demands tends to increase over time [START_REF] De Lange | A hard day's night: a longitudinal study on the relationships among job demands and job control, sleep quality and fatigue[END_REF], practitioners should keep the potential for both the beneficial and healthimpairing effects of performance pressure in mind. Keeping an eye on contextual features, as well as the availability of resources, will become increasingly important for organizations to maintain a high performing and engaging workforce in turbulent economic times.

  Figure 1. Research model

-

  Note(s): N 5 247; *p < 0.05, **p < 0.01; SD 5 standard deviation, AVE 5 average variance extracted, ASV 5 average shared variance, CR 5 composite reliability

  Figure 3. The moderating role of emotional stability on performance pressurethreat appraisal relationship

  Figure 4. The moderating role of emotional stability on performance pressurechallenge appraisal relationship

  PP 5 performance pressure, ES 5 emotional stability; x 2 5 chi-square, df 5 degree of freedom, RMSEA 5 Root mean square error of approximation, CFI 5 comparative fit index, TLI 5 Tucker-Lewis index, SRMR 5 Standardized root mean square residual

		Model	x 2	df	Δx 2	CFI TLI RMSEA SRMR
		Model I (hypothesized five-factor model)	247.93 123	-	0.96 0.95	0.06	0.05
		Model II (four-factor model: combines PP and	546.93 128	298**	0.85 0.82	0.12	0.13
		ES)
		Model III (four-factor model: combines threat	787.47 127	539.5** 0.77 0.72	0.15	0.15
		and challenge appraisals)
	Table 2.	Model IV (one-factor model)	1789.28 133 1541.4** 0.43 0.34	0.23	0.24
	Results of confirmatory factor analysis	Note(s): *p < 0.05, **p < 0.01; 0.19*		Threat Appraisal	-0.16*
		Performance Pressure		0.03 ns			Work Engagement
	Figure 2. The results of structural model with	0.46**		Challenge Appraisal	0.41**
	standardized
	coefficients. N 5 247;
	dotted lines represent direct path; are estimated;	Indirect paths			β	Bootstrapping 95% CI LLCI ULCI
	*p < 0.05, **p < 0.01	Performance pressure → Threat appraisal → Work engagement	-0.042*		-0.103	-0.001
		Performance pressure → Challenge appraisal → Work engagement	0.275**	0.128	0.489