Matteo Treleani
email: matteo.treleani@univ-cotedazur.fr

Keywords: audiovisual archives, belief, digital heritage, digital media, disinformation, fake news, interfaces, objectivity, semiotics, YouTube

Interfaces have partially replaced editors. They now administer and have industrialized the processes of content circulation. Web platforms mediatize cultural memory and one example of this is that of online audiovisual archives which are a paradigmatic case involving interfaces mediating our image of the past. Therefore, their role as an enunciative framework is clearly worthy of thought and study. We will thus use a semiotic approach based on the starting hypothesis that digital interfaces shape our belief systems through a discursive framing of content to which they give access. By analyzing two case studies, we will argue that the transparency of interfaces appears to recall the notion of "mechanical objectivity" and thus refashion the reliability of the archives. However, a final counter-analysis of a document read in the framework of an on-site consultation invites us to reshape our considerations and enlarge the perspective from semiotic visual analysis to include the social processes linked to the publication of digital heritage.

Introduction

Digital interfaces are most often perceptible, in visual terms at least. YouTube, for instance, provides us with videos through a device managed by the user and we all understand the importance of the algorithms that hide or make content visible. Clearly there can be no doubt that mediation is there and is perceptible as such. If we take the practical elements of media such as the mouse or the keyboard into account rather than just the graphic elements, we can only assume that mediation is not disguised for the user. 1 The YouTube interface requires considerable effort as a space for practice and, although it can be quickly mastered by the user, it nevertheless remains a necessity for accessing audiovisual content. And yet, this mediation does not seem to take responsibility for the enunciative dimension of the content displayed. In other words, it is often perceived as neutral from the standpoint of meaning. A considerable gap seems to exist between the content displayed and the interface displaying it. The platform merely makes content accessible to us. It transmits rather than communicates, and does not seem to be part of the meaning of the broadcast content. The paratextual elements of a document published online, like the title and description, may be the only factors considered to be determinant in interpreting the document. Most of the literature in digital studies has examined the influence of the medium on cultural practices and the esthetic dimension of digitization: the notions of relocation and remediation are an example of these viewpoints [START_REF] Bolter | Remediation: Understanding new media[END_REF][START_REF] Casetti | The Lumière galaxy: Seven keywords for the cinema to come[END_REF]. From a semiotic perspective, these phenomena can be seen as examples of reframing and genuine discursive focalizations. We will thus attempt to determine the effects of the interface as an enunciative practice, or a re-enunciation of the content displayed (Colas-Blaise 2018). We will examine the issue of digitized audiovisual archives, and thus question historical documents published online. Archives have a social impact on cultural memories, and studying their mediatization helps us understand how complex cultural memories are built through digitization [START_REF] Hoskins | The mediatization of memory[END_REF]. There is an increasing amount of audiovisual archive material in media spaces [START_REF] Ernst | Digital memory and the archive[END_REF]. This phenomenon influences what Bernard Stiegler calls "collective protentions" and thus also the collective horizons for the future (Stiegler 2018). The role of interfaces has become of considerable importance since the "archival turn"the digitization and online publication of digital heritage (de Leeuw 2012; Doueihi 2011). These images make the past visible and archival documents thus have a special role to play as memorial inscriptions, which show a privileged link with the past. They keep traces of the past and their apparent authenticity is fundamental for consolidating our belief in it. Our projections are based on the past and are expectation horizons concerning the future [START_REF] Derrida | Le mal d'archive: Impressions freudiennes[END_REF]. Studying the semiotic role of interfaces as new mediations of cultural memory is therefore important if we are to understand how cultural identities are formed. We will first propose the hypothesis that interaction and meaning are linked since a way of interacting with content may constitute an interpretative mode. We will then analyze two case studies of audiovisual archives remediated on YouTube in which the interaction produces specific effects, like the anonymization of images and the confusion of genres. Next, we shall attempt to define the notion of digital objectivity as one possible semiotic result of interactive mediation through web platforms. Finally, a counter-analysisthe observation of how a digitized record is consulted through a platform in situ at France's National Audiovisual Institute (Ina)will invite us to adopt a complementary standpoint.

On interfaces and belief

This article explores the strange paradox between the enunciative camouflage of an element, in this case the interface, and the fact that this interface is actually visually and perceptibly present. This inconsistency seems to indicate a difference between perception and interpretation, or embodiment and narration. The seminal text "Remediation" by Richard Bolter and Jay David Grusin uses a fairly traditional dialectic of aesthetics studies namely the contrast between the visual presence of the representative regime and the transparency of representation. In the audiovisual field, we refer to a dichotomy between an editing practice that makes itself visible, reminding us of its role as a spectator by denouncing the artifice of fiction, and a transparent edit aimed at giving viewers the actions filmed without mediation, or, better still, which uses a rhetorical strategy aimed at remaining hidden so the spectator does not notice it. Bolter and Grusin apply these esthetic terms to the relationship to media and speak about the presence and transparency of interfaces. Their two paradigmstransparent immediacy and hypermediationare of course rhetorical strategies in which mediation is always ontologically present and is even the condition of viewing but is hidden in esthetic terms. They also explicitly speak of "visual styles" and insist on the perceptual dimension of this shaping. This dichotomy must be looked at through a heuristic lens to effectively understand media relations. Hypermediation and transparent immediacy make a good starting point to understanding how interfaces can disguise themselves. Consequently, we may refer to interfaces that are hidden through rhetorical and visual strategies to the extent that this camouflage may prevent the user from being aware of their editorial role. However, our main point here is that the kind of presence we want to understand is not just perceptive in nature. Most of the interfaces we use in the digital regime are hypermediations which are visible, present and not transparent however their semiotic role is not clearly evident for the user. The digital mediation's enunciative role is mostly disguised even if the user is aware of its presence. YouTube displays videos and the website, its algorithms or the way we access content have been thoroughly examined, but there has been less thought about the way it intervenes in the discursive dimension of video content. Interfaces are present and yet they are perceived as non-epistemically

The degree zero of digital interfaces importanta place of power for digital mediations (see the notion of "trivialité": Jeanneret 2014).

3 Regimes of interaction and regimes of belief Our hypothesis will be that the role of interfaces as a way of interacting with content may constitute a regime of belief that frames content and actualizes some interpretative paths.

Eric Landowski analyzed the interaction between a subject and the other (or another subject) from a semiotic point of view to theorize different regimes of interaction. As relational practices, these regimes may produce effects of meaning with meaning produced from the starting point of a practical relation. The idea that an interactive practice could generate an interpretative mode is similar to the notion of genre as an element which constitutes a horizon of expectation. The interaction may constitute a sort of genre, which frames content and directs interpretation in a certain way. Landowski considered four regimes of interaction: manipulationmaking another actor do something; programmingan interaction based on pre-established rules; chancewhere randomness prevails; and adjustmentbased on the mutual exchange between the interacting actors [START_REF] Landowski | Les interactions risquées[END_REF]. Manipulation means using the other actor like in the relationship between teacher and student, for instance; programming means following certain procedures which are independent from the specific interaction (the kind of interaction between subjects that we may find in a game, for example); chance is an unpredictable interaction (unexpectedly meeting another person); and adjustment is a shared interaction in which one actor does not prevail over the other (as in the case of a dance, for instance). This classification reflects ways of seeing an interactionheuristic modesand not a real typology, which means that we can find all these dimensions within a single interaction.

Each regime can be used to analyze the interaction a user has with the YouTube interface, for instance. Here the poles we consider are the user and the interface. We may use YouTube as an instrument to find what we are interested in (manipulation); however, our exchanges are programmed by the rules of the system (programming); serendipity may bring us to documents that we would have never found otherwise (chance); and the interface adapts to our profile through recommendation algorithms that follow our search and visualization history (adjustment; Cardon 2015). These four modalities will help us in our analysis of the two case studies. We will see that interaction leads to a regime of belief that seems to confer a status of objectivity to the proposed documents. We will argue that this is a form of digital or computational objectivity, based on the interface's potential to interact. Our study will be focused on two institutions specialized in the conservation and distribution of audiovisual archives, the French National Audiovisual Institute (Ina) and the Italian Istituto Luce, with their online platforms on YouTube. We will observe the role of the globalization and industrialization of a mediated memory in the framework of what has been called the "platform paradigm" [START_REF] Burgess | From "broadcast yourself" to "follow your interests": Making over social media[END_REF]. YouTube is a global platform, used by two different national archives, whose histories and ways of distributing archives online are similar and can be compared. These examples can be used, from a methodological point of view, as paradigmatic cases in the sense discussed by [START_REF] Agamben | The signature of all things: On method[END_REF]. Agamben interpreted Foucault's notion of paradigm and posited that a case can be used to interpret the problematic context that produced it. If a given context produced such a case then it can be used to shed light on that environment to better understand it. Our two case studies are thus symptomatic instances of this problematic topic. The final counter-example will help us to isolate patterns and define general tendencies.

A case of fake history

Istituto Luce operates a channel on YouTube called Cinecittà Luce. The channel shows an interesting playlist of newscasts from the 1930s called Cronache dall'Impero (Chronicles from the Empire). It is a series of propaganda movies from the fascist period about Italian colonies. An auto-ethnographic approach is useful for describing the viewing experience when visiting the channel. A video captured our attention on 17 April 2018 namely a report from 1936 entitled "Cronache dall'Impero da Mogadiscio."2 The 2-min report talks about an Italian governor (General Santini) arriving in Somalia. Typically of Luce reports, pompous music and a reporter's voice play over the shots of the governor parading before the troops at the airport with some institutional salutations exchanged between Ethiopian and Italian soldiers. However this short film shows the complexity of the mediations which we usually encounter when watching images from the past in some kind of a naturalized way. This footage was produced in 1936 by the Istituto Luce which was then the propaganda arm of the fascist regime. It was archived and digitized by an institution with the same name today but which does not have the same objectives and intentions. It went from being a producer and broadcaster to being a heritage institution. The Luce logo and time code are burned into the video. All Luce videos have this time code, which must have been added during the passage of the original film to Betacam. The YouTube platform also shows the name of the account that posted the video (Cinecittà Luce) and the publication date (June 15, 2012). Underneath the video there is also a title, commentary, and credits that were obviously absent from the original 1936 report. There is a multitude of layers of mediation namely the platform, the YouTube channel, the institution that digitizes and preserves the archives, and the producer of the original report. They are historical, professional, technical layers which are also authoritative in nature. The reliability of archival records is judged by the presence of some iconic elements from the institution that preserves these records. For example, the presence of the logo is seen as "trustworthy" and elicits a sense of confidence in the user. It is believed that these archives were not manipulated or modified by Istituto Luce.

However, similar videos suggested by YouTube's algorithms attracted our attention, particularly two videos in the right-hand column of the interface called "La Guerra d'Etiopia" ("The War of Ethiopia") and "Colonialismo: le verità nascoste" ("Colonialism: the hidden truths"). For information, this auto-ethnographic example is linked to a specific profile and date and we know that recommendation algorithms lead to the right column changing according to the IP address, YouTube profile, and so forth. The first film is a re-edit recounting the story of the fascist war in Ethiopia. It was shot as a documentary and does not seem to have any particularly political stance. During this visit to YouTube we did actually not notice straight away that we had left the official channel of Istituto Luce and passed to a content author's unverified account. More precisely, the author, "Studio del Bianco," based in the Italian town of Fano, seems to produce historical documentaries. His website offers an interview with an expert and "teacher" who studies the poet Ezra Pound. This poet's collusion with fascism is well known, especially in Italy, where his name is even used in an extreme right-wing movement (Casa Pound). It takes a rather detailed search to find the web page of this photographic studio. The fact that the video is suggested by the algorithm next to the Istituto Luce videos is somewhat concerning as we stumbled upon it as if it were a reliable document without realizing that the channel watched was no longer that the institute's. Even if viewers do notice the change, a logo appears on the screen from the archival document but of course the author is no longer the same. The least we can say is that the multitude of mediations blurs the enunciator's visibility. We do not know if the author has just uploaded an archival document taken from elsewhere or if the footage was manipulated before being posted, nor do we know the document's real origins. The fact that the difference between a verified video and an unverified one is not particularly clear is even more problematic for users who navigate these pages without paying close attention.

The second video, called "Colonialismo: le verità nascoste," announces straightaway its conspiracy theorist's standpoint. The author, "NeroItalico" (which makes reference to the paramilitary Blackshirts in fascist Italy) clearly displays his political orientation and the title claims there are "hidden truths" or secrets that need revealing as in most conspiracy theories. The user does not hide his leanings. Among his publications, we find a video entitled "Il fascismo è per sempre" ('fascism is forever'), which has been taken down by YouTube. The use of archives is very similar to the use of documents in most of what is usually called "fake news" today. This kind of content is often based on the use of authentic archival documents which have been manipulated or misinterpreted by the author. A recent European report on these issues avoids the term "fake news," stating that the real problem is disinformation, "which involves content that is not actually or completely 'fake' but fabricated information blended with facts, and practices that go well beyond anything resembling 'news' to include some forms of automated accounts used for astroturfing, networks or fake followers, fabricated or manipulated videos, targeted advertising, visual memes and more" (European Commission 2018). The question is more complex than a simple dichotomy between fake and real. Authentic documents are often used to misinterpret history, for instance.

These two examples show the subtle link between videos recommended on the platform and the tricky dimension of publishing archives online the authors of which have to be verified to judge the authenticity of the footage. Therefore, the issue of authenticity for digital archives has also to face the issue of how documents circulate as well as their mediatization online [START_REF] Duranti | Reliability and authenticity: The concepts and their implications[END_REF]. This issue is not just a traditional question that can be confronted, for instance, in archive based documentaries: the mediations create confusion regarding genre, author, and enunciative instances that become difficult to individuate.

Moving the Eiffel Tower

A second case study will help us better understand the issues involved in publishing audiovisual archives online. In 2014, we analyzed a very special case in which recontextualization prevented the right framework being adopted to interpret the contents of an archive video [START_REF] Treleani | Mémoires audiovisuelles[END_REF]. In 2009, Ina published on its website (Ina.fr) a report produced by the French national agency ORTF (Office de Radiodiffusion Télévision Française) from 1964 in which an engineer explains in an interview that the Eiffel Tower is to be moved a hundred meters to make room for a municipal stadium. The date was April 1, 1964 and this was indeed an April Fool's Day joke. The reception of this joke is interesting to study. At least two bloggers wondered whether the information was true or false. The statistical relevance of these two reactions is not the issue, but the mere fact that a person could actually think there was a project to move the Eiffel Tower invites us to investigate the contextual elements that make this information credible when its contents clearly are not. One blogger, Marion, says that she found "an Ina record" with an engineer's

The degree zero of digital interfaces interview3 and considers that the fact that it is from an archive means that it is proof of the past. That this record comes from Ina makes the content reliable and verifies its authenticity. This example effectively shows the importance of contextualization in archival practices of distribution, in which the institution becomes an editor rather than just a "gatekeeper of knowledge" [START_REF] Noordergraaf | Who knows television? Online access and the gatekeepers of knowledge[END_REF].

When the Ina discussed this case, the institution modified the descriptive notice and added an explanation referring to a "trick" as they realized the viewer needed clues to avoid misinterpreting the video. This is a summary of what happened in 2009 but the question remains valid today. A video called "Why the Eiffel Tower must be moved? Archive -Ina" was published by Ina on its official YouTube channel on 31 March 2016 (with April's Fool's Day in mind). 4 The descriptive note displays the French word trucage added by Ina to clarify the genre of the report. However, one of the three comments (an account named Daichi San) says "yet it has never moved, there is no stadium." This example shows that the joke is still effective. Even if the joke is clearly explained by the interface, some users still believe in the veracity of the report. We can list myriad reasons why users still believe in this joke (see [START_REF] Treleani | Mémoires audiovisuelles[END_REF], but there are two reasons in particular that seem interesting here. First, clearly the ORTF video becomes a record and, once published online, assumes the status of a media document that circulates alongside other documents in the digital environment at the rapidity of consultation typical of the web. This means that its status has changed from that of a report to a record and then from a record to digital content. So, the regime used to read these documents is fairly different from the one a user would adopt to read an archival document. Most Internet users do not watch videos all the way to the end, and 6 out of 10 Internet users share information without having read it [START_REF] Gabielkov | Social clicks: What and who gets read on Twitter?[END_REF]. Secondly, the multitude of layers that constitute the access to the document makes it difficult to understand the author of the video. The video is simply linked to the authority of the Ina, an institute that guarantees the content's reliability to the extent that users feel they do not have to question its trustworthiness. In any case, although the contextualization is necessary, it does not suffice to guarantee that users will understand the joke. Daichi San is unlikely to have read the notice or perhaps did not use it to interpret the video (the word trucage may not refer to the content of the video).

In these two casesthe Eiffel Tower being moved and the manipulated propaganda videos of the fascist colonial periodthe archival content seems to be considered as being objective in nature. We shall argue that this feeling of objectivity is a consequence of how the content is consulted.

Anonymized images

Drawing a parallel with certain narratological notions may be of interest here. The fictional pact is based on a particular form of belief: the je sais bien mais quand même ('I know that, but still') analyzed by Frédéric Lambert, in a parallel analysis of semiotic and anthropological questions [START_REF] Lambert | Je sais bien mais quand même[END_REF]. When you read a novel or watch a film, you know that it is only fiction but you want to believe it. The enunciative frameworkgenre, for examplehas some importance in this belief assumption. You need to know where the story ends and what its limits are in order to adhere to it. The perimeter of the narration and the context in which it intervenes are fundamental to understanding which interpretative mode to choose in order to read it. The genre defines the belief in the story's content: is it about the real world or is it fiction, for instance? [START_REF] Jost | Que signifie parler de « réalité » pour la télévision?[END_REF]. So, what happens with content displayed through a web platform? Frédéric Lambert points out that in our media regimes, images circulate between cultural industries, news media and art and this permeability of media creates confusion between fact and fiction (Lambert 2014: 116).

As a result, the issue of anonymity becomes particularly interesting. This confusion between genres and media involves questioning the author's role of a message, which becomes complex to identify. According to Lambert, cultural industries are factories of anonymous messages and "without an author, our images are authoritative" (Lambert 2014: 116). On YouTube, we see the name of the institution that preserves the archive (Istituto Luce or Ina). This contributes to distancing or dissociating the idea of an enunciator of the video from that of the online archive. This instance seems to lend authority to images that would not be referable to a clearly identifiable enunciative instance. They are "re-enunciated" instead of being simply enunciated by a subject, which means that the institution only shows something which has been shot by someone else, and this simply guarantees the reliability of the content, but does not explicitly "say it." Thus, although the institution intentionally published the video, the video was not intentionally meant to be seen by us (at least not today and not on the web). The platform just makes it accessible. The authority of the institution means we should be able to believe what is shown. On the one hand, once the images have been anonymized, they belong to the past, and thus become proof of it. On the other hand, the absence of a clear enunciator implies a lack of point of view on the narrated facts. These archives have been shot by someone, broadcast on TV, then archived, digitized, and redocumentarized by an institution [START_REF] Pédauque | La rédocumentarisation du monde[END_REF]. Some meta-data have been selected by the institution for the footage's online presence before it is published on a platform (YouTube) that provides access via its interface. These technical, semiotic, cultural, and even historical mediations are difficult to grasp in their complexity for a user.

If we apply Landowski's interaction regimes to these two examples, we will see how the technique is perceived as a purely instrumental element that does not participate in the enunciation of the displayed content. The regime of manipulation gives us a sense of power: the interface is used, it allows us to find data ourselves, independently from the tool that gives us access to it. The user is thus responsibilized and becomes the real enunciator of the document because s/he actually found it (Marion says: "J'ai trouvé une archive de l'Ina"). The multiple mediations can be seen as a large number of pre-programmed rules. These are fixed systems, but they overlap and eventually blur the lines between them, thereby hiding the sources and identity of the enunciating instances. We therefore have a regime in which we manipulate the interface, and the multitude of overlapping programs gives rise to a form of chance where we have a feeling of power, based on interaction. At the same time, there is a sense of incertitude of what will be displayed due to the algorithms. Chance and the responsibilization of viewers contribute to building a feeling of objectiveness, or, at least, not of intentionality (the lack of a clear subjective instance responsible for the document's content). More generally, the fact that technology is a non-human element seems to give a sentiment of objectivity to the instruments used to access content. The presentation is not experienced as a frame showing an enunciative intention but only presents it to us "logistically."

Degree zero contextualization

The enunciative dimension of interfaces is often hidden when talking about the online publication of content, and this issue is especially clear when talking about data. For example, the philosopher Michel Serres went so far as to defend the idea that knowledge would be available online without mediation or a need for mediation.5 Antoinette Rouvroy conceptualized this phenomenon, which she called the "regime of digital truth," based on Michel Foucault's regime of truth, as a mode for categorizing reality (Rouvroyand Stiegler 2015).The same kind of critique was put forward by Manovich (recalling that "Data does not just existit has to be generated, " Manovich 1999: 224) and as Lisa Gitelman also asserts, the very idea that raw data may exist is oxymoronic6 (Gitelman 2013: 12).

From a semiotic point of view, this kind of criticism is evocative of Roland Barthes' Writing Degree Zero, published in 1953. Thus we may speak about a degree zero contextualization in which this notion of contextualization refers to the intentional activity of a content manager that inscribes content within a specific digital context. Data visualization sites rely on rhetorical strategies that hide the enunciating instances but the online publication of audiovisual records seems to hide these instances without intentionality. In the case of interfaces which display data to us, mediation is always clearly present and is not disguised by a rhetorical technique but it still manages to appear insignificant. The issue has a social dimension as well as a rhetorical one. Julia [START_REF] Bonaccorsi | Le monde de l'Open data: Les jeux sémiotiques et esthétiques de la 'visualisation' comme rhétorique de la transparence[END_REF] has worked on the question of transparency regarding esthetic issues related to data visualization. She states that "on the one hand, the act of making data available is defined as evidence of informational or even political transparency … ; on the other hand, the calculation of data and the representation of their analysis are considered as indicators of public ownership by civil society and its representatives (experts, media, entrepreneurs, citizens)." The social dimension is thus important: the fact of showing a public ownership of data is a first step in creating value through data, which means that the social act of making data (or archives) visible is a first step to legitimating content through something that is socially perceived as an act of "revealing something." The logic of revelation is a singular notion that is linked to a legitimation of content which are discovered. 7 Here again the responsibilization of the user can be seen to be important to make the content reliable. We have to find it to believe in it. The fixation of belief is often the result of an inquiry that legitimates the results as is explained in Peircean philosophy ; see Borges and Gambarato 2019 for an application of Peircean approach to the circulation of fake news on Facebook). In other words, the regime of interaction may produce a sentiment of empowerment within the user who in turn becomes the enunciator of the visualized content. The content is raw so the viewer is responsible for what is shown and what is shown thus becomes objective. In a certain way, records become objective since they are anonymized and thus not intentionally enunciated. They do not give a clear context of genre which would affect their meaning and they were found through an interface that helps us discover them.

result of a research: " … during the eighteenth century, data changed connotation. It went from being reflexively associated with those things that are outside of any possible process of discovery to being the very paradigm of what one seeks through experiment and observation." (Rosenberg 2013: 36). 7 About the link between truth and secret, see Eco (2017: 328).

The degree zero of digital interfaces

Mechanical objectivity

This way of perceiving a document's objectiveness is coherent with certain notions of objectivity. In their history of the concept, Lorraine [START_REF] Daston | Objectivity[END_REF] underline the arrival around the mid-19th century of what they call a mechanical or non-interventionist objectivity, linked to the development of technical instruments used in observation and measurement. The principle of this form of objectivity, which then contributed to the conception of modern objectivity, is based on the delegation of observation to a technical instrument. The idea is to set aside any subjectivity of the observer, in order to guarantee the reliability of the observation. The delegation to another entityin this case an instrumentreduces the influence of subjectivity.

In this case, the concept moves away from an idea of objective vision as the closest representation of nature ("truth to nature"). For instance, the use of the daguerreotype in some medical discourses is not justified by a better adherence of the representation to the object, with more details, for example. Drawings by professional artists were used before the arrival of the daguerreotype and were much more detailed and useful for scientific description. The daguerreotype introduced viewing difficulties that did not exist before (problems of focus, the black-and-white, and so on). Even though these imperfections made viewing difficult, they did not lead to questioning of the objectivity of reproduction. On the contrary, they become a mark of objectivity, and their presence serves as a guarantee to the reproduction's authenticity and objectivity.

Delegating representation to a technical authority gives the reader the responsibility of interpreting what is presented to him. Since the observer only gives an image of reality that undergoes technicaland therefore non-subjectivemediation, the reader is the real interpreter and observer of data. There is therefore a shift, from the observer to the reader: mediation is perceived as non-intentional. This concept of objectivity seems well suited to describe how we feel about data visualizations and digital interfaces for audiovisual archives. The interface is indeed a technical mediation in which the tool is only mastered, and semiotically transparent. However, the specificities linked to digital culture can show another type of objectivity linked to mechanical objectivity, but with certain specificities that define it more effectively.

Digital objectivity

Published online content undergoes a process that has been called "editorialization" which is usually automatic. An editorial team can decide on a certain amount of paratextual elements (records, keywords, descriptions, titles, etc.) but algorithms usually shape the context in which the content is received (Vitali Rosati 2018). Automating the editorial process is a digital specificity that imparts a feeling of nonintentional or non-subjective contextualizationalthough not entirely a form of objectivity. 8 The automation of publication has to be coupled with the interaction and the active role of the user. Databases give us the possibility to search through indefinite catalogs. The interface can thus be seen as a dispositif, in a Foucauldian sense, in which the user is involved through a process of "subjectivation." The dispositif assigns a role to the subject who is able to act through the interface and does not merely have a passive role.

Where mechanical objectivity aims to confine the subjectivity of the observer in order to let the results of the inquiry speak for itself, thereby responsibilizing the viewer, we can thus affirm that digital objectivity exacerbates the position of the observer by empowering him. The observer becomes a user who searches for his archives, produces his own statistics, and therefore assumes the role of co-enunciator of the content. The interface is a technical mediationa black box in which the human being (an engineer or designer, for example) intervenes through processes that are multiple and too complex to find a clear and homogeneous intentionalitywhich actually reinforces this feeling.

Counter-analysis

We can list two effects of the recontextualization of videos on the YouTube platform: the anonymization of the images and the multiplication of mediations. These elements make it difficult to interpret certain features that determine an image's meaning, such as the enunciative instance (who says what) or an image's genre. As a result, these effects lead to a form of co-enunciation. We explained the reactions of the users of the footage about the Eiffel Tower moving through the responsibilization of the user who seems to be the co-enunciator of the records displayed. However, we performed a counter-analysis to confirm the relevant elements in the interface that contribute to creating this feeling. In linguistics, this would be some kind of "commutation test," to verify the validity of our results and understand the pertinent elements to consider for making meaning. Consequently, we analyzed the consultation of a document through the Ina interface on-site which can be done in the rooms of the Ina at the Bibliothèque National de France in Paris. Ina's workstations feature software called Hyperbase that provides a very deep consultation of the 8 Bruno Bachimont (2014) talks about the reification of cultural contents produced by digitization.

The degree zero of digital interfaces national base of French television, for example. This counter-analysis should validate our hypothesis made on the analysis on YouTube.

The first remark to be made concerns the situation. The consultation takes place using a specific workstation where one can only access the tools for consulting the Ina database. There is no web browser for instance although Internet can obviously be consulted using a laptop, but another device is thus required. Moreover, online archives are distributed to us as media objects whereas here we look for them which mean our attitude is very different and presupposes the critical questioning of sources. The user will therefore be very attentive, focused on the contents and its context. The archives consulted via Hyperbase are not mediatized in the industrial sense; they are not made accessible through a distribution that targets the greatest number of people and are instead given access in a paradigm closer to traditional archiving even though this can sometimes be done remotely (Ina's consultation centers are spread throughout France in municipal or university libraries). The question of authority does not arise as the video is not paired with other videos that do not come from archives or are not kept by the same institution. Our investigation is carried out within the Ina and everything else is clearly outside this significant context. The paradigm of access is therefore opposed to the paradigm of broadcasting. As a consequence, the status of the archive and its mediatization seem to be the most important factors to consider.

As regards the interface itself, the interaction involves a conscious manipulation of tools that are particularly complex to manage, less immediate, and which sometimes give unsatisfactory or uninteresting results. It is necessary to follow very precise rules and to have acquired a certain level of experience to use them effectively. A great deal of time is required to understand their procedures and yet chance remains a very important element in archival work. Many parameters have to be chosen and a period of adaptation is necessary in order to be able to use it effectively. There is a delay between a request for video content and being able to view it which also makes it less "accessible." It remains quite possible to come across misinterpretations due to a lack of context given by the interface, which is often reduced to the title and meta-data written by archivists who look to achieve some level of objectiveness, but it is still clear that any misinterpretation will be interpreted and questioned by users who finds themselves in a context and situation in which critically questioning the sources is their very purpose.

This counter-analysis would appear to encourage us to review the conclusions of the observations from a semiotic approach of interfaces and almost to invalidate them. Digital devices do involve a series of contextual interpretative problems but most seem to be due to a phenomenon that is more linked to the situation and a sociology of practices of heritage institutions than semiotic or media-based: the act of publication that constitutes the mediatization itself implies some semiotic consequences. In other words, the main issue seems to be linked to the cultural practices of publishing contents online, independently from their status (thus included historical content). An effect of meaning of objectivity still seems to be a valid analysis but it may be difficult to demonstrate the effective role of the interface. This has to be framed in a more general contemporary way of using web contents.

Final considerations

The comparison between the consultation of archives through the industrialized and standardized platform of YouTube and the on-site consultation shows the dichotomy between an interaction with archival documents based on distance and one that shows a tendency toward proximity. It could be argued that putting archives online after their digitization is a form of technical reproducibility of documents from the past aimed at "bringing things closer humanly and spatially" as Benjamin's put it, seeing this process already at work with photography and cinema [START_REF] Benjamin | The work of art at the age of its mechanical reproduction[END_REF][START_REF] Treleani | Qu'est-ce que le patrimoine numérique? Lormont: Le Bord de l'Eau[END_REF]). The mediatized interface of YouTube is a way to bring archives closer but on-site consultation keeps a high level of distance that creates a dynamic of critical awareness. Proximity ultimately blurs the semiotic references for interpreting a document: the identification of genres, enunciators and the status of the document becomes blurred and these phenomena can give rise to meaningful effects that may lead to feelings of objectivity by questioning the relationship of an archive's authenticity.

Finally, the notion of distance should be reintroduced, as should our consideration of the role it plays in user interactions with heritage documents. The philosopher Byung Chul Han, in analyzing the transparency society, states, "the society of transparency views all distance as negativity to be eliminated. Distance represents an obstacle to the acceleration of the flows of communication and capital. In keeping with its inner logic, the society of transparency eliminates every form of distance" (Han 2015: 15). Faced with the radically generalized accessibilitywhether immediate or remoteof any form of cultural product, what seems desirable for our highly mediated society in terms of its relationships with the past is a rehabilitation of the importance of distance as an identity and interpretative factor: "Given the pathos for transparency that has laid hold of contemporary society, it seems necessary to gain practical familiarity with the pathos of distance" (Han 2015: 4).

The degree zero of digital interfaces

"The computer instantiates a practice not a presence, an effect not an object. In other words, if cinema is, in general, an ontology, the computer is, in general, an ethic" (Galloway

2012: 22).

Treleani

https://www.youtube.com/watch?v=9Ki973DicCo.The degree zero of digital interfaces

http://www.parcoursnumeriques-pum.ca/introduction-39.

https://www.youtube.com/watch?v=g_HZWPN6XZc.

The degree zero of digital interfaces

"Que transmettre ? Le savoir ? Le voilà, partout sur la Toile, disponible, objectivé. Le transmettre à tous ? Désormais tout le savoir est accessible à tous. Comment le transmettre ? Voilà, c'est fait"(Serres 2012: 19).

Daniel Rosenberg analyzes the evolution in the use of the term "data" and he observes the semantic shift from something that is used rhetorically in order to support an argumentation to the


Marc Castella
email: marc.castella@int-evry.fr

Pierre Comon
email: pcomon@i3s.unice.fr

Blind Separation of Instantaneous Mixtures of Dependent Sources

  L'archive ouverte pluridisciplinaire

Introduction

Independent Component Analysis is now a well recognized concept, which has fruitfully spread out to a wide panel of scientific areas and applications. Contrary to other frameworks where techniques take advantage of a strong information on the diversity, for instance through the knowledge of the array manifold in antenna array processing, the core assumption is much milder and reduces to the statistical mutual independence between the inputs.

However, this assumption is not mandatory in Blind Source Separation. For instance, in the case of static mixtures, sources can be separated if they are only decorrelated when their nonstationarity or their color can be exploited. Other properties such as the fact that sources belong to a finite alphabet can alternatively be utilized [START_REF] Li | Finite-alphabet information and multivariate blind deconvolution and identification of linear systems[END_REF][START_REF] Comon | Contrasts, independent component analysis, and blind deconvolution[END_REF] and do not require statistical independence.

Inspired from [START_REF] Comon | Blind identification and source separation in 2 × 3 under-determined mixtures[END_REF][START_REF] Comon | Non-linear inversion of underdetermined mixtures[END_REF], we investigate the case of dependent sources, without assuming nonstationarity nor color. To our knowledge, only few references have tackled this issue [START_REF] Hyvärinen | A quasi-stochastic gradient algorithm for variancedependent component analysis[END_REF][START_REF] Cardoso | Multidimensional independent component analysis[END_REF].

Mixture model and notations

We consider a set of N source signals (s i (n)) n∈Z , i = 1, . . . , N . The dependence on time of the signals will not be made explicit in the paper. The sources are mixed, yielding a P -dimensional observation vector x = (x(n)) n∈Z according to the model:

x = As (1)
where s = (s 1 , . . . , s N ) T , x = (x 1 , . . . , x P ) T and A is a P × N matrix called the mixing matrix. We assume that A is left-invertible. Source separation consists of finding a P ×N separating matrix B such that its output y = Bx corresponds to the original sources. When only the observations are used for this, the problem is referred to as the blind source separation (BSS) problem. Introducing the N × N global matrix G BA, the BSS is problem is solved if G is a so-called trivial matrix, i.e. the product of a diagonal matrix with a permutation: these are well known ambiguities of BSS.

In this paper, we will study separation criteria as functions of G. Source separation sometimes proceeds iteratively, extracting one source at a time (e.g. deflation approach). In this case, we will write y = bx = gs where b and g = bA respectively correspond to a row of B and G and y denotes the only output of the separating algorithm. In this case, the separation criteria are considered as functions of g. Finally, we denote by E {.} the expectation operator and by Cum {.} the cumulant of a set of random variables. Cum 4 {y} is equivalent to Cum {y, y, y, y} and, for complex variables, Cum 2,2 {y} stands for Cum {y, y, y * , y * }.

Examples and properties of dependent sources

We introduce in this section different cases of vector sources that are dependent and that will be considered in this paper.

Three dependent sources

Binary phase shift keying (BPSK) signals have specificities that will allow us to obtain source vectors with desired properties. By definition, BPSK sources take values s = +1 or s = -1 with equal probability 1/2. We define the following source vector: A1. s (s 1 , s 2 , s 3 ) T where s 1 is BPSK; s 2 is real-valued non Gaussian, independent of s 1 and satisfies E {s 2 } = E s 3 2 = 0 and s 3 = s 1 s 2 . Interestingly, the following lemma holds true: Lemma 1. The sources s 1 , s 2 , s 3 defined by A1 are obviously mutually dependent. Nevertheless they are decorrelated and their fourth-order cross-cumulants vanish, that is:

Cum {s i , s j } = 0 except if i = j, (2) Cum {s i , s j , s k , s l } = 0 except if i = j = k = l. (3)
Proof. Using the definition of s 1 , s 2 and their independence, one can easily check that E {s 1 } = E {s 2 } = E {s 3 } = 0. For these centered random variables, it is known that cumulants can be expressed in terms of moments:

Cum {s i , s j } = E {s i s j } (4)
Cum

{s i , s j , s k , s l } = E {s i s j s k s l } -E {s i s j } E {s k s l } -E {s i s k } E {s j s l } -E {s i s l } E {s j s k } (5)
Using again the definition of s 1 , s 2 and their independence, it is then easy to check all cases of equations ( 4) and ( 5) and to verify that these 4th order cross-cumulants are indeed null. On the other hand, the third order cross-cumulant reads:

Cum {s 1 , s 2 , s 3 } = E {s 1 s 2 s 3 } = E s 2 1 s 2 2 = E s 2 1 E s 2 2 > 0 (6)
and this proves that s 1 , s 2 , s 3 are mutually dependent.

⊓ ⊔

Depending on s 2 , more can be proved about the source vector defined by A1. For example, if the probability density function of s 2 is symmetric, then s 1 and s 3 are independent. On the contrary s 2 and s 3 are generally not independent. An even more specific case is obtained when s 2 is itself BPSK. In this case, one can check that the sources (s 1 , s 2 , s 3 ) are pairwise independent, although not mutually independent.

Pairwise independent sources

We now investigate further the case of pairwise independent sources and introduce the following source vector:

A2. s = (s 1 , s 2 , s 3 , s 4 ) T where s 1 , s 2 and s 3 are independent BPSK and s 4 = s 1 s 2 s 3 .

This case has been considered in [START_REF] Comon | Blind identification and source separation in 2 × 3 under-determined mixtures[END_REF], where it has been shown that

∀i ∈ {1, . . . , 4}, Cum {s i , s i , s i , s i } = -2 , Cum {s 1 , s 2 , s 3 , s 4 } = 1 (7)
and all other cross-cumulants vanish. The latter cumulant value shows that the sources are mutually dependent; although it can be shown that they are pairwise independent. It should be clear that pairwise independence is not equivalent to mutual independence but in an ICA context, it is relevant to recall the following proposition, which is a direct consequence of Darmois' theorem [7, p.294]:

Proposition 1. Let s be a random vector with mutually independent components, and x = Gs. Then the mutual independence of the entries of x is equivalent to their pairwise independence.

Based on this proposition, the ICA algorithm in [START_REF] Comon | Independent component analysis, a new concept[END_REF] searches for an output vector with pairwise independent component. Let us stress that this holds only if the source vector has mutually independent components: pairwise independence is indeed not sufficient to ensure identifiability as we will see in Section 4.2.

Complex valued sources

We consider quaternary phase shift keying (QPSK) sources which by definition take their values in {1, ı, -1, -ı} with equal probability 1/4 and we define the following source vector:

A3. s = (s 1 , s 2 , s 3 , s 4 ) T where s 1 , s 2 and s 3 are mutually independent QPSK and

s 4 = s 1 s 2 s 3 s 4 .
Based on the Equations ( 4) and ( 5) which hold for the above centered sources, one can check the following proposition:

Lemma 2. The sources in A3 are dependent and satisfy Cum {s 1 , s 2 , s 3 , s * 4 } = 1. However, they are second-order decorrelated and all their 4th order circular crosscumulants (i.e. with as many conjugates as non-conjugates) vanish, that is:

Cum s i , s * j = 0 and Cum {s i , s j } = 0 except if i = j, (8)
Cum

{s i , s j , s * k , s * l } = 0 except if i = j = k = l (9)
4 ICA algorithms and dependent sources

Independence is not necessarily required

The sources given by A1 provide us with a specific example of dependent sources that are sucessfully separated by several ICA methods:

Proposition 2. Let y = gs where the vector of sources is defined by A1. Then, the function

g → |Cum 4 {y}| α , α ≥ 1 ( 10
)
defines a MISO contrast function, that is, its maximization over the set of unit norm vectors ( g 2 = 1) leads to a vector g with only one non-zero component.

Proof. The above proposition follows straightforwardly from Lemma 1 since the proof of the validity of the above contrast functions only relies on the property in Equation ( 3).

⊓ ⊔

Considering again the argument in the proof, one should easily notice that the above proposition can be generalized to the case of sources which satisfy:

A4. s = (s 1 , . . . , s 3K ) where: ∀i ∈ {0, . . . , K -1}, s 3i+1 is BPSK; s 3i+2 is non Gaussian and satisfies E {s 3i+2 } = E s 3 3i+2 = 0; s 3i+3 = s 3i+1 s 3i+2 ; and the random variables {s 3i+1 , s 3i+2 ; i = 0, . . . , K -1} are mutually independent.

In addition, the above result can be generalized to MIMO (multiple input/multiple output) contrast functions as defined in [START_REF] Comon | Independent component analysis, a new concept[END_REF] [2]: Proposition 3. Let y = Gs where the vector of sources is defined by A1. Then the function:

G → N i=1 |Cum 4 {y i }| α , α ≥ 1 (11)
is a MIMO contrast, that is, its maximization over the group of orthogonal matrices leads to a solution G which is a trivial matrix (permutation, scaling).

Many classical algorithms for BSS or ICA first whiten the data: it is known that when doing so, they constrain matrix G to be orthogonal. In particular so does the algorithm proposed in [START_REF] Comon | Independent component analysis, a new concept[END_REF], which relies on the contrast function in (11). It justifies that this algorithm successfully separates the sources A1. Actually, any algorithm relying on a prewhitening and associated with a contrast function based on the vanishing of the fourth-order cross cumulants (e.g. JADE) is able to separate sources such as A1.

Pairwise independence is not sufficient

We now consider the pairwise independent sources given by A2 and show that pairwise independence is not sufficient to ensure identifiability of the ICA model. We first have the following preliminary result:

Lemma 3. Let y = gs where the vector of sources is defined by A2. Assume that the vector (s 1 , s 2 , s 3 ) takes all 2 3 possible values. If the signal y has values in {-1, +1}, then g = (g 1 , g 2 , g 3 , g 4 ) is either one of solutions below:

∃i ∈ {1, . . . , 4} g i = ±1, and: ∀j = i, g j = 0 ∃i ∈ {1, . . . , 4} g i = ±1/2, and: ∀j = i, g j = -g i (12)

Proof. If y = gs, using the fact that s 2 i = 1 for i = 1, . . . , 4, we have with the particular sources given by A2:

y 2 = g 2 1 +g 2 2 +g 2 3 +g 2 4 +2 g 1 g 2 +g 3 g 4 s 1 s 2 + g 1 g 3 +g 2 g 4 s 1 s 3 + g 2 g 3 +g 1 g 4 s 2 s 3
Since (s 1 , s 2 , s 3 ) take all possible values in {-1, 1} 3 , we deduce from y 2 = 1 that the following equations necessarily hold:

g 2 1 + g 2 2 + g 2 3 + g 2 4 = 1 g 1 g 2 + g 3 g 4 = g 1 g 3 + g 2 g 4 = g 2 g 3 + g 1 g 4 = 0 (13)
First observe that values given in (12) indeed satisfy ( 13). Yet, if a polynomial system of N equations of degree d in N variables admits a finite number of solutions 3 , then there can be at most d N distinct solutions. Hence, we have found them all in (12), since (12) provides us with 16 solutions for (g 1 , g 2 , g 3 , g 4 ).

⊓ ⊔

Using the above result, we are now able to specify the output of classical ICA algorithms when applied to a mixture of sources which satisfy A2.

Constant modulus and contrasts based on fourth order cumulants The constant modulus (CM) criterion is one of the most known criteria for Blind Source Separation. In the real valued case, it simplifies to:

J CM (g) E y 2 -1 2
with: y = gs (14) Proposition 4. For the sources given by A2, the minimization of the constant modulus criterion with respect to g leads to either one of the solutions given by Equation (12).

Proof. We know that the minimum value of the constant modulus criterion is zero and that this value can be reached (for g having one entry being ±1 and other entries zero). Moreover, the vanishing of the constant modulus criterion implies that y 2 -1 = 0 almost surely and one can then apply Lemma 3.

⊓ ⊔

3 One can show that the number of solutions of (13) is indeed finite.

A connection can now be established with the fourth-order autocumulant if we impose the following constraint:

E y 2 = 1 (or equivalently g = 1 since y = gs) (15)
Because of the scaling ambiguity of Blind Source Separation, the above normalization can be freely imposed. Under (15), we have Cum

4 {y} = E y 2 -1 2 -2
and minimizing J CM (g) thus amounts to maximizing -Cum 4 {y}. Unfortunately, since Cum 4 {y} may be positive or negative, no simple relation between |Cum 4 {y}| and J CM (g) can be deduced from the above equation. However, we have the following proposition:

Proposition 5. Let y = gs where the vector of sources is defined by A2. Then, under the constraint (15) ( g = 1), we have:

(i) The maximization of g → -Cum 4 {y} leads to either one of the solutions given by Equation (12). (ii) |Cum 4 {y}| ≤ 2 and the equality |Cum 4 {y}| = 2 holds true if and only if g is one of the solutions given in Equation (12).

Proof. Part (i) follows from the arguments given above. In addition, using multilinearity of the cumulants and ( 7), we have for y = gs:

Cum 4 {y} = -2 g 4 1 + g 4 2 + g 4 3 + g 4 4 + 24 (g 1 g 2 g 3 g 4 ) (16)
The result then follows straightfowardly from the study of the polynomial function in Equation ( 16). Indeed, optimizing (16) leads to the following Lagrangian:

L = -2 4 i=1 g 4 i + 24 4 i=1 g i -λ 4 i=1 g 2 i -1 (17)
After solving the polynomial system which cancels the Jacobian of the above expresssion, one can check that all solutions are such that |Cum 4 {y}| ≤ 2. Details are omitted for reasons of space. Part (ii) of the proposition easily follows.

⊓ ⊔

Similarly to the previous section, the above proposition can be generalized to MIMO contrast functions. In particular, this explains why, for a particular set of mixing matrices such as that studied in [START_REF] Comon | Blind identification and source separation in 2 × 3 under-determined mixtures[END_REF], the pairwise maximization algorithm of [START_REF] Comon | Independent component analysis, a new concept[END_REF] still succeeded: a separation has luckily been obtained for the considered mixing matrices and initialization point of the algorithm, but it actually would not succeed in separating BPSK dependent sources for general mixing matrices.

Let us stress also that the results in this section are specific to the contrast functions given by (10) or (11). In particular, these results do no apply to algorithms based on other contrast functions such as JADE, contrary to the results in Sections 4.1 and 4.3.

Complex case

The output given by separation algorithms in case of complex valued signals may differ from the previous results which have been proved for real valued signals only. Indeed, complex valued Blind Source Separation does not always sum up to an obvious generalization of the real valued case [START_REF] Eriksson | Complex random vectors and ICA models: Identifiability, uniqueness and separability[END_REF]. We illustrate it in our context and show that, quite surprisingly, blind separation of the sources given by A3 can be achieved up to classical inderterminations of ICA. This is in contrast with the result in Equation ( 12) where additionnal indeterminacies appeared. First, we have: Lemma 4. Let y = gs where the vector of sources is defined by A3. Assume that the vector (s 1 , s 2 , s 3 ) takes all 4 3 possible values. If the signal y is such that its values satisfy |y| 2 = 1, then g = (g 1 , g 2 , g 3 , g 4 ) satisfies: ∃i ∈ {1, . . . , 4} |g i | = 1, and: ∀j = i, g j = 0

(18)

Proof. If y = gs, using the fact that |s i | 2 = 1 for i = 1, . . . , 4, we have with the particular sources given by A3:

|y| 2 = 4 i=1 |g i | 2 + i =j g i g * j s i s * j (19)
Since (s 1 , s 2 , s 3 ) take all possible values in {1, ı, -1, -ı} 3 , we deduce from |y| 2 = 1 that the following equations necessarily hold: are contrast functions, that is, their maximization leads to g satisfying (18).

|g 1 | 2 + |g 2 | 2 + |g 3 | 2 + |g 4 | 2 = 1 g 1 g * 2 = g 1 g * 3 = g 1 g * 4 = g 2 g * 3 = g 2 g 4 * = g 3 g * 4 = 0 (
Proof. The validity of the first contrast function is obtained with the same arguments as in the proof of Proposition 4: we have |y| 2 m.s. = 0, which yields (20) via (19). In the case of independent sources, the proof of the validity of the second contrast involves only cumulants with equal number of conjugate and non conjugate variables: invoking Lemma 2, one can see that the same proof still holds here.

⊓ ⊔

Note that the same arguments can be applied to ICA methods such as the pairwise algorithm in [START_REF] Comon | Contrasts, independent component analysis, and blind deconvolution[END_REF] or JADE [START_REF] Cardoso | Blind beamforming for non gaussian signals[END_REF]. Figure 1 illustrates our result.

Proposition 6 .

 6 20) Solving for the polynomial system in the variables |g 1 |, |g 2 |, |g 3 | and |g 4 |, we obtain that the solutions are the ones given in Equation (18). ⊓ ⊔ Constant modulus and fourth-order cumulant based contrasts In contrast with Propositions 4 and 5 we have the following result: Let y = gs where the sources satisfy A3. Then, the functions: g → -E |y| 2 -1 2 and: (21) g → |Cum 2,2 {y}| under constraint E |y| 2 = 1 (22)

Fig. 1 .

 1 Fig. 1. Typical observed separation result of the sources A3 with the algorithm JADE (left: sensors, right: separation result)


J L Nandrino
email: nandrino@univ-lille3.fr

Keywords: Tracas quotidiens, névrosisme, personnalité, santé des étudiants, NEO-PI-R daily hassles, neuroticism, personality, health of students. NEO-PI-R

L'objectif de cette recherche est d'étudier le lien entre la personnalité, évaluée avec le NEO PI-R, et les tracas quotidiens (stresseurs mineurs) des étudiants, évalués au moyen d'une échelle validée et spécifique à cette population de jeunes adultes. A partir des réponses de 165 étudiants (âge moyen = 21.2 ans), cette recherche montre une corrélation significative entre le tracas des étudiants et le facteur Névrosisme qui correspond à l'anxiété, au manque d'estime de soi et à la nervosité (p<0.001).

L'étude met également en évidence l'existence d'un profil de personnalité en fonction du niveau faible ou élevé de tracas perçu. Les étudiants sensibles aux stress mineurs par rapport aux étudiants « non sensibles » se différencient au niveau de 7 facettes de personnalité du NEO PI-R (anxiété, colère-hostilité, dépression, timidité sociale, impulsivité, vulnérabilité, autodiscipline,). Cette étude permet de montrer le lien complexe entre la perception d'éléments stressants et la personnalité.

Elle représente prés de 4 % de la population totale (2.3 millions de personnes en 1997). La croissance des effectifs devenant de plus en plus importante au sein des facultés [START_REF] Grignon | Les conditions de vie des étudiants[END_REF] ; l'étudiant d'aujourd'hui est, de ce fait, un étudiant de « masse » [START_REF] Lapeyronnie | Campus Blues : Les étudiants face à leurs études[END_REF]. Cette caractéristique du monde universitaire semble contribuer à un mécanisme de désocialisation venant amplifier les sentiments de solitude et d'anonymat chez l'étudiant. Ainsi, les troubles de l'humeur et les troubles anxieux constituent les principaux problèmes de santé des jeunes (Albarello,1997 ;Chatelain,1997 ;[START_REF] Coulon | Le métier d'étudiant -L'entrée dans la vie universitaire[END_REF] Haut Comité de Santé Publique (HCSP), 1997).

Les étudiants sont exposés à de nombreux agents stressants parmi lesquels les tracas quotidiens (« daily hassles ») ou stresseurs mineurs qui correspondent à « des expériences et conditions de vie quotidienne estimées comme frappantes, saillantes, nocives ou comme menaçantes vis-à-vis du bien-être" constituent des agents importants d'installation de troubles du comportement ou de troubles mentaux [START_REF]Puzzles in the Study of Daily Hassles[END_REF].

L'intérêt croissant porté à l'étude des tracas quotidiens vient du fait qu'ils apparaissent être de meilleurs prédicteurs de la santé physique et mentale des individus que les événements de vie et ce, quel que soit l'âge des personnes confrontées à ses stresseurs mineurs [START_REF] Kanner | Comparaison of two modes of stress measurement: Daily Hassles and Uplifts versus Major Life Envents[END_REF]Plancherel & al.,1997 ). Il semble en effet, que les événements de vie aient un impact sur la santé par l'intermédiaire des tracas quotidiens (Plancherel et al 1997).

En ce qui concerne l'étude du lien entre les tracas et la santé mentale des étudiants, quelques rares études existent à ce jour. Chez les jeunes canadiens, scolarisés du collège à l'université, le fait d'avoir trop de choses à faire, trop de responsabilité et pas assez de temps libre, sont les principales sources de tracas [START_REF] Kohn | The Inventory of High-School Students'Recent Life Experiences : a decontaminated measure of adolescents' hassles[END_REF]. Aux Etats-Unis, chez des étudiants en médecine, les principaux tracas repérés sont de type académique et liés aux relations sociales. Ils s'intensifient en cours d'année et sont corrélés positivement aux problèmes de santé mentale (en particulier l'anxiété et la dépression) (Wolf & al., 1991). Chez les étudiants Français, les tracas les plus gênants sont spécifiques au monde étudiant (la peur du chômage, le manque d'indépendance matérielle et financière, ne pas avoir les capacités nécessaires pour réussir ses études). Les préoccupations envers les proches, le manque de temps et certains faits de société sont également des sources de tracas aux yeux de ces étudiants (Réveillère & al., 2001).

Les tracas quotidiens trouvent leur origine dans "le style caractéristique des personnes, leur environnement routinier et leur interaction" [START_REF] Kanner | Comparaison of two modes of stress measurement: Daily Hassles and Uplifts versus Major Life Envents[END_REF]. Ils dépendent des mécanismes d'évaluation primaire et secondaire et des stratégies de coping.

Ils sont donc influencés par des facteurs personnels et contextuels. Plusieurs études [START_REF] Kanner | Comparaison of two modes of stress measurement: Daily Hassles and Uplifts versus Major Life Envents[END_REF]Plancherel & al., 1997) ont montré des effets de l'âge et de l'activité sur l'évaluation des tracas quotidiens. En ce qui concerne le facteur sexe, il semble que son influence soit plus importante chez les enfants, les adolescents et les jeunes adultes [START_REF] Kanner | Comparaison of two modes of stress measurement: Daily Hassles and Uplifts versus Major Life Envents[END_REF]Seiffge-Krenke, 1994).

Face au stress imposé par le système universitaire, la personnalité de l'étudiant va transparaître dans les jugements et les modes de réactions. Certaines études ont mis en évidence que des traits de personnalité, comme l'anxiété ou le névrosisme, prédisposent ces jeunes adultes à être plus particulièrement sensibles aux stresseurs mineurs [START_REF] Kohn | Hassles, health and personality[END_REF]Hudiburg & al., 1997 ;[START_REF] Gershuny | The relation between personality and anxiety : findings from a 3-year prospective study[END_REF]. D'autres, en revanche, vont dans le sens d'une correspondance entre l'Ouverture à l'expérience et les tracas quotidiens (Hudiburg & al., 1997 ). Ces résultats mettent donc en évidence la complexité de cette interaction entre la personnalité et le stress. & al, 2001). C'est un auto-questionnaire de type " papier-crayon ", dont le temps de passation varie de 10 à 15 minutes selon les sujets.

Il comprend 65 items répartis de manière aléatoire dans 10 domaines différents : santé, travail, relations interpersonnelles, argent, matériel, transport, société, temps, estime de soi et divers.

L'échelle de tracas quotidiens donne deux scores. L'un correspond à la gêne ressentie, l'autre à la fréquence d'apparition sur une échelle de quatre degrés allant de 0 à 3.

Pour la gêne, 0 correspond à " pas du tout gêné " et 3 à " extrêmement gêné ". Pour la fréquence, 0 correspond à " jamais " et 3 à " souvent ". Le score en gêne (GEN) et le score en fréquence (FRE), variables numériques, ne peuvent donc pas dépasser 195 (65*3).

L'évaluation de la personnalité de notre population (165 étudiants) a été effectuée à partir du NEO PI-R (Inventaire de Personnalité Révisé), mis au point par [START_REF] Costa | Inventaire NEO PI-R[END_REF].

Le NEO PI-R est un instrument d'auto-évaluation dont l'objectif est de permettre au sujet de se décrire lui-même sur la base de 240 items répartis en cinq facteurs : le Névrosisme, l'Extraversion, l'Ouverture, l'Agréabilité et la Conscience.

* Présentation des cinq facteurs :

Leur étude va permettre d'appréhender de façon globale la personnalité du sujet.

Soulignons que chaque échelle du NEO PI-R ne doit pas être considérée comme une mesure de pathologie mentale, mais évalue une dimension de la personnalité normale.

-Névrosisme (N) : Ce domaine oppose l'adaptation (ou stabilité émotionnelle) à l'inadaptation Ce facteur identifié comme un facteur de risque de chronicité de la dépression (Scott et al 1992 ;1995), semble en plus être un facteur de vulnérabilité aux stresseurs mineurs repérable avant l'installation d'un trouble dépressif avéré. On peut ainsi penser que névrosisme, stresseurs mineurs et troubles de l'humeur soient intimement liés.

Les résultats soulignent l'existence de deux profils de personnalité correspondant aux niveaux faible et élevé de gêne à l'échelle de tracas quotidiens.

En effet, les étudiants stressés, en comparaison des étudiants peu stressés, se différencient de manière significative au niveau de dix facettes de personnalité du NEO PI-R. Les traits de personnalité qui entrent en jeu dans ce profil sont : l'anxiété, la colère/hostilité, la dépression, la timidité sociale, l'impulsivité, la vulnérabilité, la compliance, le sens du devoir, l'autodiscipline et la délibération.

A un niveau plus qualitatif, les profils de personnalité de nos sujets stressés vs non stressés présentent certaines caractéristiques :

-En règle générale, les sujets exprimant une gêne faible (GEN<42.1) ne présentent pas de vulnérabilité majeure au stress. Bien au contraire, ils se sentent capables de faire face aux difficultés.

Ils sont plutôt curieux et ont tendance à préférer la nouveauté aux choses familières.

Ils semblent davantage éprouver des émotions positives que négatives et manifestent une certaine satisfaction par rapport à la vie qu'ils mènent. Ils sont pour la plupart motivés et font preuve de ténacité lorsque la situation l'exige.

-Prés de 80% des sujets exprimant une gêne élevée (GEN >= 134.5) [ 11,3 ; 42,1 ] Gêne faible [ 42,1 ; 72,9 ] Gêne moyenne faible [ 72,9 ; 103,7 ] Gêne moyenne [ 103,7 ; 134,5 ] Gêne moyenne élevée [ 134,5 ; 165,3 ] Gêne



  Sensibilité aux tracas quotidiens et personnalité des étudiants : importance du facteur névrosisme Nandrino J.L. 1 , Réveillère C. 2 , Sailly F. 1 , Moreel V. 1 , Beaune D. 1 Université espace d'une quinzaine d'années, la population étudiante Française a doublé.

(

  ou névrosisme). Le sujet ayant un score élevé à N aura d'une part tendance à éprouver des affects négatifs (tristesse, culpabilité, peur,...), d'autre part à rencontrer des difficultés dans la gestion du stress et des tensions internes. A l'inverse, des notes basses à N seront synonymes de stabilité émotionnelle.-Extraversion (E) : L'extraversion caractérise davantage les personnes sociables, grégaires, actives, aimant la fête et se montrant plutôt optimistes. En ce qui concerne l'introversion, il s'agit de sujets réservés et indépendants. -Ouverture (O) : L'ouverture à l'expérience rassemble plusieurs qualités telles que la curiosité, l'imagination active et la tendance à vivre de manière plus intense les émotions (positives ou négatives). Les sujets obtenant un faible score à O sont plus conservateurs, préférant les situations familières à la nouveauté. -Agréabilité (A) : Cette dimension va de paire avec l'altruisme. L'individu agréable est sympathique, prêt à aider les autres. En revanche, le sujet ayant une note basse à A se montre égocentrique et préfère la compétition à la coopération. -Conscience (C) : La conscience renvoie à la volonté de réussir et à la détermination. Dans le meilleur des cas, une note élevée à C est à mettre en lien avec la réussite scolaire et professionnelle. Cependant, cela peut conduire l'individu à une fatigue excessive et à des exigences inadaptées. Chaque facteur se caractérise par 6 facettes spécifiques (Tableau I). Nous obtenons donc cinq scores globaux (N, E, O, A et C), ainsi que 30 sous-scores (correspondant aux 30 facettes). Le NEO PI -R a été utilisé conjointement à l'échelle de tracas quotidiens auprès de notre échantillon réunissant 165 étudiants. Les passations se sont déroulées de façon collective. Elles ont été standardisées pour tous les sujets. Le temps de passation était d'environ une heure, dont une dizaine de minutes pour l'échelle de tracas quotidiens. Résultats Les liens entre tracas quotidiens et les cinq dimensions de personnalité : L'étude du lien entre les tracas quotidiens et la personnalité s'appuie sur le calcul des coefficients de corrélation entre les variables de notre échelle (GEN et FRE), et celles caractérisant les cinq facteurs de personnalité du NEO PI-R (Névrosisme, Extraversion, Ouverture, Agréabilité et Conscience). Les résultats (cf tableau II) montrent que le score en gêne perçue et la note standard obtenue au facteur Névrosisme du NEO PI-R, sont corrélés positivement et significativement. Nous relevons un coefficient de corrélation de 0.417 (r²=0.174 ; p<0.001). En revanche, la variable « gêne » et les quatre autres facteurs du NEO PI-R ne sont pas corrélés de manière significative. Tracas quotidiens et les trente facettes du NEO PI-R De façon à étudier de manière plus approfondie le lien entre les tracas quotidiens et les traits de personnalité, deux groupes de sujets ont été constitués sur la base du score en gêne : les étudiants obtenant un score faible (GEN<42.1) et ceux ayant une note élevée (GEN >=134.5) (cf tableau IIII a, b). Dans un premier temps, les coefficients de corrélation entre la variable GEN de ces sujets et leurs scores aux facettes ont été calculés. Puis, les deux groupes de sujets ont été comparés au moyen du test non paramétrique de Mann-whitney. * Corrélations entre le score en gêne et les facettes du NEO PI -R Parmi les 30 facettes du NEO PI-R, 7 sont corrélées de manière significative avec le score en gêne perçue (cf tableau IV) et 3 présentent des tendances (C3 : p=.10 ; A4 : p=.05 ; C6 : p=.054) . Chacune des 6 facettes du Névrosisme, est corrélée positivement et significativement avec le score en gêne. Ces coefficients de corrélation sont compris entre 0.453 et 0.7. Une facette de l'Agréabilité et trois facettes de la Conscience sont corrélées négativement avec le score en gêne. Pour vérifier s'il existe des profils de personnalité en lien avec le niveau de stress perçu, nous avons procédé à une comparaison entre les groupes de sujets stressés (n=23) et les sujets non stressés (n=6). * Comparaison entre les 2 groupes d'étudiants stressés vs non stressés Les étudiants exprimant une gêne élevée et ceux faiblement gênés se différencient de manière significative selon dix facettes de personnalité du NEO PI-R. Ces dernières sont celles pour lesquelles nous avons obtenu des corrélations significatives avec la variable GEN (cf tableau V). Les étudiants ayant un score GEN élevé, ont des notes significativement supérieures à celles des étudiants peu stressés en ce qui concerne les six facettes du Névrosisme. En revanche, les étudiants stressés obtiennent des scores inférieurs en A4 (compliance), C3 (sens du devoir), C5 (autodiscipline) et C6 (délibération), en comparaison avec les étudiants peu tracassés. Discussion Les résultats de l'étude montrent la relation entre la sensibilité aux stresseurs mineurs et le type de personnalité des étudiants. En effet, le coefficient de corrélation entre le score en gêne perçue de l'échelle de tracas quotidiens et le facteur Névrosisme du NEO PI-R est significatif (r=0.417 ; p<0.001). Ainsi, l'étudiant présentant une personnalité empreinte d'anxiété, d'une faible estime de soi, d'émotions négatives (tristesse, culpabilité, ...) sera davantage perturbé par les soucis de tous les jours. Un lien entre la personnalité et la fréquence d'occurrence des stresseurs mineurs a également été relevé, en particulier concernant les facteurs Névrosisme (r=0.52 ; p<0.0001) et Extraversion (r=-0.181 ; p<0.05). Ce résultat renforce l'idée selon laquelle la personnalité de l'étudiant entre en jeu dans l'appréhension des tracas quotidiens. Ces données vont dans le sens des travaux de Gershuny & Sher (1998) qui montrent un lien significatif entre les tracas quotidiens et le Névrosisme. Il est intéressant de noter que ce facteur est d'ailleurs un facteur de risque de chronicité de la dépression. Les patients qui présentent un risque élevé de récidives sont justement ceux dont le score de névrosisme est élevé[START_REF] Akiskal | Chronic depressions. Part 1 : Clinical and familial chracteristics in 137 probands[END_REF][START_REF] Duggan | Does personnality predict long-term outcome in depression ?[END_REF] Scott et al 1992). L'étude déjà ancienne deWeismann et al (1976), qui rend compte du suivi sur quatre ans de 150 femmes dépressives montrent que deux facteurs prédisent la chronicité des symptômes dépressifs : la qualité de la compliance au traitement et l'existence d'un degré élevé de névrosisme.

  présentent une instabilité émotionnelle marquée. Plus précisément, la majorité d'entre eux semble exprimer un haut niveau d'anxiété et éprouve souvent des affects dépressifs. En outre, ils ressentent très facilement de la colère et peuvent ainsi paraître hostiles dans leurs réactions interpersonnelles. Notons également, qu'ils ont des difficultés à gérer les situations embarrassantes et qu'ils se découragent lorsque surviennent des complications. Environ un tiers de ces étudiants est néanmoins à l'aise en société et apprécie le contact et les échanges avec autrui. En revanche, 17% des sujets stressés semblent manquer d'assurance et avoir des difficultés à exprimer leurs opinions dans certaines situations. La répartition des étudiants au niveau des différents degrés de l'Ouverture montre qu'aucune catégorie ne prédomine. Parmi les sujets stressés certains sont ouverts sur le plan de l'expérience et d'autres sont plus conventionnels et conservateurs. La moitié Pour les Services Universitaires de Médecine Préventive et de la Prévention de la Santé, le repérage de ces traits de personnalité pourrait être effectué, dans une perspective de santé publique, auprès des étudiants consultants pour malaise psychique diffus, afin de pouvoir intervenir en amont de l'installation de troubles francs. PLANCHEREL, B., BETTSCHART W., BOLOGNINI M., DUMONT M., HALFON O. -Influence comparée des événements existentiels et des tracas quotidiens sur la santé psychique à la préadolescence, Neuropsychiatrie Enfance Adolescence, 43(3) :126-138, 1997.

				Tableau II
	Variables Névro	Extra	Ouver	Agréa	Consc	GEN	FRE
	Névro	--	-.247007*	.11136	-.042711	-.07882	.41713*	.520816*
	d'entre eux manifestent une certaine méfiance envers les intentions d'autrui et un manque p=.0017* p=.1541 p=.5862 p=.3148 p=.0007* p=.0000*
	de générosité et de volonté d'aider ceux qui en ont besoin. Ils sont pour la plupart peu consciencieux (57%) et semblent présenter une faible estime d'eux-mêmes et sont peu préparés à affronter la vie. En général, ils ont des difficultés à se motiver pour mener à bien leurs objectifs. Il semble que les caractéristiques individuelles de l'étudiant stressé (sentiment de colère, timidité sociale, agressivité, ...) peuvent représenter un obstacle à la mise en place de liens sociaux soutenants, contrairement à l'étudiant faiblement gêné qui apparaît plus conciliant et ouvert au dialogue. De même, en ce qui concerne les stratégies d'ajustement, nos résultats suggèrent que l'étudiant tracassé utilisera plus souvent des stratégies de retrait (évitement, attitude fataliste), tandis que le sujet faiblement gêné aura davantage recours aux stratégies actives (soutien social, recherche d'informations) et aux stratégies internes (analyse du problème et planification d'une solution). Le facteur névrosisme semble lié à une sensibilité exacerbée aux stresseurs mineurs. Sa présence conduit à développer des stratégies adaptatives spécifiques pouvant constituer un terrain de vulnérabilité pour le développement ultérieur de troubles anxieux ou de (2001).Etudes des tracas quotidiens des étudiants : liens avec la santé perçue, Annales Médico.Psychologiques (sous presse). SCOTT, J., ECCLESTON, D., BOYS, R. (1992). Can we predict the persistence of depression ? British Journal of Psychiatry, 161 : 633-637. SEIFGE-KRENKE, I. (1994) Les modes d'ajustement aux situations stressantes du développement : comparaison d'adolescents normaux et d'adolescents perturbés, L'orientation Scolaire et Professionnelle. 32 : 313-327,. WEISSMAN, M., KASL, M., KLERMAN, G.L. (1976) Follow-up of depressed women after maintenance treatment. American Journal of Psychiatry 133: 757-760. WOLF, T.M., KIDDLING, G. E., BURGESS, L. A (1991).Psychosocial changes during the Tableau I Névrosisme Extraversion Ouverture Agréabilité Conscience Anxiété Chaleur Rêveries Confiance Compétence Colère-Hostilité Grégarité Esthétique Droiture Ordre Dépression Assertivité Sentiments Altruisme Sens du devoir Timidité sociale Activité Actions Compliance Recherche de réussite Impulsivité Recherche de sensations Idées Modestie Autodiscilpline Vulnérabilité Emotions positives Valeurs Sensibilité Délibération Extra -.247007* p=.0017* --.317619* p=.0007* .198016* p=.0118* .224812* p=.0044* -.060785 p=.438 -.181349* p=.0201* Ouver .11136 p=.1541 .317619* p=.0007* --.067064 p=.3927 .045293 p=.5635 -.059958 p=.4449 .02451 p=.7554 Agréa -.042711 p=.5862 .198016* p=.0118* .067064 p=.3927 --.118355 p=.1308 -.028211 p=.7198 -.024828 p=.7524 Consc -.07882 p=.3148 .224812* p=.0044* .045293 p=.5635 .118355 p=.1308 ---.066663 p=.3956 -.144158 p=.0654 GEN .41713* p=.0007* -.060785 p=.438 -.059958 p=.4449 -.028211 p=.7198 -.066663 p=.3956 --.742897* p=.000* FRE .520816* -.181349* .02451 -.024828 -.144158 troubles de l'humeur. REVEILLERE , C., NANDRINO, J.L., SAILLY, F., MERCIER, C., MOREEL, V. p=.0000* p=.0201* p=.7554 p=.7524 p=.0654
	first year of medical school, Medical education, 25 :174-181,.

SCOTT, J., WILLIAMS, J.M.G.,

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