In four experiments we used eye-tracking to investigate biases in looking behaviour during visual decision making tasks. In Experiment 1, participants viewed arrays of images of photographic art and decided which image was preferred (from a set of either two or eight alternatives). To analyze gaze behaviour during the decision we identified dwells (where a dwell is a series of consecutive fixations on a decision alternative). This analysis revealed two forms of gaze bias in the period prior to the response. Replicating prior findings (Shimojo, Simion, Shimojo, & Scheier, 2003), just prior to the response we found an increase in the frequency of dwells on the chosen item. In addition, throughout the decision, dwells on the chosen item were longer than dwells on other items. This pattern of biases was extremely similar across preference and non-preference decision instructions, but overall the biases were more pronounced in eight alternative decisions than in two alternative decisions. In Experiment 2 we manipulated the number of decision alternatives while controlling for differences in the stimulus displays. Participants viewed displays containing six everyday items, and chose either which of two sets of three items was the most expensive (two alternative set selection task) or which of the six items was the most expensive (six alternative item selection task). Consistent with Experiment 1, participants exhibited greater selectivity in their processing of stimulus information in the six alternative decisions compared to the two alternative decisions. In Experiments 3 and 4 we manipulated stimulus exposure in order to test predictions derived from the Gaze Cascade model (Shimojo et al., 2003). In Experiment 3, participants performed an eight alternative decision in which four of the items had been pre-exposed prior to the decision. In Experiment 4, stimulus exposure was manipulated during the ongoing decision using a gaze-contingent methodology. While these manipulations of stimulus exposure had strong effects on gaze bias, the specific predictions of the model were not supported. Rather, we suggest an interpretation based on prior research, according to which the gaze bias reflects the selective processing of stimulus information according to its relevance to the decision task.

In four experiments we used eye-tracking to investigate biases in looking behaviour during visual decision making tasks. In Experiment 1, participants viewed arrays of images of photographic art and decided which image was preferred (from a set of either two or eight alternatives). To analyze gaze behaviour during the decision we identified dwells (where a dwell is a series of consecutive fixations on a decision alternative). This analysis revealed two forms of gaze bias in the period prior to the response. Replicating prior findings (Shimojo, Simion, Shimojo, & Scheier, 2003), just prior to the response we found an increase in the frequency of dwells on the chosen item. In addition, throughout the decision, dwells on the chosen item were longer than dwells on other items. This pattern of biases was extremely similar across preference and non-preference decision instructions, but overall the biases were more pronounced in eight alternative decisions than in two alternative decisions. In Experiment 2 we manipulated the number of decision alternatives while controlling for differences in the stimulus displays. Participants viewed displays containing six everyday items, and chose either which of two sets of three items was the most expensive (two alternative set selection task) or which of the six items was the most expensive (six alternative item selection task). Consistent with Experiment 1, participants exhibited greater selectivity in their processing of stimulus information in the six alternative decisions compared to the two alternative decisions. In Experiments 3 and 4 we manipulated stimulus exposure in order to test predictions derived from the Gaze Cascade model (Shimojo et al., 2003). In Experiment 3, participants performed an eight alternative decision in which four of the items had been pre-exposed prior to the decision. In Experiment 4, stimulus exposure was manipulated during the ongoing decision using a gaze-contingent methodology. While these manipulations of stimulus exposure had strong effects on gaze bias, the specific predictions of the model were not supported. Rather, we suggest an interpretation based on prior research, according to which the gaze bias reflects the selective processing of stimulus information according to its relevance to the decision task.

In order to attract the attention of users current online shopping environments often involve the use of dynamic display changes such as animation, flashing or rotating text, and pop-up boxes. While there is some experimental evidence that supports the effectiveness of such changes for the purpose of capturing attention, such changes might also distract the user and hinder task performance. Thus, a key usability challenge for the designers of such environments involves balancing the need to attract attention with the desire to minimize any interruption of the performance of users. To date there is very little systematic investigation of the influence of display changes on consumers¡¦ attention and decisions during the browsing of online shopping web sites. The main goal of the present experiments was to research factors that might be important in determining the influence of such display changes. To accomplish that experimental tasks were created that resembled some aspects of the visual decision process and dynamic changes that occur during online shopping. However, in order to permit greater experimental control, the information environment used in the present tasks was substantially simplified as compared to online environments. Specifically, in 3 experiments, participants¡¦ eye movements were monitored while they chose between 2 alternatives, each represented by a set of visual images, with one set placed on the top of the screen and the other on the bottom. Immediately prior to this decision participants performed one or more binary decisions based on subsets of these images. On some trials, images were spatially swapped in the display presented during the final decision as compared to a prior presentation. Across experiments, we manipulated the relevance of the change to task performance as well as the recency of the information that was modified. By analyzing behavioral and eye movement measures, we documented evidence that participants flexibly and effectively accommodated to a variety of display changes. However, there was cost associated with display changes in the form of longer viewing times. In addition, task relevant changes and changes to recently viewed information were generally more disruptive. We discuss the implications of the present findings for the design of online shopping web sites and for future research that would attempt to generalize the present findings to more complex and more realistic online environments.

De nombreuses études ont relevé un biais perceptif (BP) gauche, c’est-à-dire une tendance à utiliser préférentiellement les informations issues de l’hémi-visage gauche (du point de vue de l’observateur), lors du traitement des visages. Ce BP pourrait être lié à la dominance de l’hémisphère droit pour le traitement des visages. Par ailleurs, certaines études ont mis ce BP en lien avec un biais oculomoteur (BO) gauche : l’observateur effectue des fixations en nombre et/ou en durée supérieurs sur l’hémi-visage gauche (Butler et al., 2005 ; Megreya & Havard, 2011). Au cours du vieillissement, le BP gauche semble être toujours présent, mais d’apparition plus tardive, nécessitant un temps d’exposition aux visages plus long (Butler & Harvey, 2008 ; Coolican et al., 2008). Dans ce travail de thèse, nous avons étudié l’évolution de ces deux biais au cours du vieillissement au cours d’une tâche de jugement de genre, à l’aide de visages normaux et chimériques (composés de moitiés de visages d’homme et de femme) en manipulant le nombre de saccades permettant d’explorer le visage (aucune, 1, 2 et 3 saccades) et la position de présentation des visages (Haut, Bas, Centre, Gauche et Droite). Bien que dans l’ensemble, les personnes jeunes témoignent d’un BP gauche, cela n’est pas le cas des participants âgés. En outre, ce BP dépend de la position de présentation des visages (BP de proximité pour les positions latérales), mais également du nombre de saccades exécutées (BP gauche apparaissant à partir de la réalisation d’une saccade). En outre, une certaine variabilité interindividuelle est notée, certains participants présentant un BP droit et d’autre une absence de BP. Le BO dépend également de la position de présentation des visages et reste stable au cours du vieillissement. Il semble résulter d’une combinaison de l’effet du centre de gravité (Bindemann et al., 2009) et de l’effet de rang (Kapoula, 1985), la position d’arrivée se situant autour du centre du visage, orientée légèrement vers le point de fixation initial. Enfin, ce BO n’est pas affecté par le BP des participants, qu’ils soient jeunes ou âgés, l’exploration des visages étant la même qu’ils répondent en se basant sur la partie gauche ou droite des visages. Dans l’ensemble, ces résultats remettent en question l’explication jusqu’ici avancée pour ces deux biais, à savoir la dominance de l’HD pour le traitement des visages. / Previous studies demonstrated a left perceptual bias while looking at faces, observers using mainly information from the left side of a face (from the observer point of view) to make a judgment task. Such a bias is consistent with right hemisphere dominance for face processing and has been sometimes linked to a left gaze bias, i.e. more and longer fixations on the left side of the face (Butler et al., 2005; Megreya & Havard, 2011). In the course of aging, the left perceptual bias is still observed, but seems to require a longer exposure duration to faces (Butler & Harvey, 2008; Coolican et al., 2008). Here, in several experiments we recorded eye-movements during a gender judgment task, using normal and chimeric faces (made from two different half-faces of a male and a female) presented at the top, bottom, left or right relative to the central fixation point or at the center. Young and older participants performed the judgment task by remaining fixated on the fixation point or after executing one, two or three saccades. Even if young participants presented an overall left perceptual bias, it was not the case for older participants. Moreover, the perceptual bias depended on face position (a proximity bias was observed for lateral positions) and the number of allowed saccades (the perceptual bias was present when a saccade was executed). An important inter-individual variability was also observed. Indeed, some participants presented a left perceptual bias, while others presented a right perceptual bias or none at all. The gaze bias was also function of face position and is steady while growing older. This gaze bias seems to depend on the combination of two effects: the center-of-gravity effect (Bindemann et al., 2009) and the range effect (Kapoula, 1985). The saccade landing position was located around the center of the face, slightly oriented toward the initial fixation position. No apparent link between gaze and perceptual biases was found in any experiments, for both groups, meaning that a perceptual bias was not systematically coupled to saccades made toward the side of the face which was used to perform the gender judgment. Those results challenge the overall explanation put forward for those two biases that is the right hemisphere dominance for face processing.