Upper and lower visual field differences : an investigation of the gaze cascade effect

The purpose of the current thesis was to investigate the role of gaze direction, when making preference decisions. Previous research has reported a progressive gaze bias towards the preferred stimuli as participants near a decision, termed the gaze cascade effect (Shimojo, Simion, Shimojo & Scheir, 2003). The gaze cascade effect is strongest during the final 1500 msec prior to decision (Shimojo et al.). Previous eye-tracking research has displayed natural viewing biases towards the upper visual field. However, previous investigations have not investigated the impact of image placement on the gaze cascade effect. Study 1 investigated the impact of presenting stimuli vertically on the gaze cascade effect. Results indicated that natural scanning biases towards the upper visual field impacted the gaze cascade effect. The gaze cascade effect was reliably seen only when the preferred image was presented in the upper visual field. Using vertically paired stimuli study 2 investigated the impact of choice difficulty on the gaze cascade effect. Similar to study 1 the gaze cascade effect was only reliably seen when the preferred image was presented in the upper visual field. Additionally choice difficulty impacted the gaze cascade effect where easy decisions displayed a larger gaze cascade effect than hard decisions. Study 3 investigated if the gaze cascade effect is unique to preference decisions or present during all visual decisions. Judgments of concavity using perceptually ambiguous spheres were used and no gaze cascade effect was observed. Study 3 indicated that the gaze cascade effect is unique to preference decisions. Results of the current experiments indicate the gaze cascade effect is qualified by the spatial layout of the stimuli and choice difficulty. Results of the current experiments are consistent with previous eye-tracking research demonstrating biases towards the upper visual field and offering support for Previc’s theory on how we interact in visual space

Fertility affects asymmetry detection not symmetry preference in assessments of 3D facial attractiveness

Consistent with theories from evolutionary psychology, facial symmetry correlates with attractiveness. Further, the preference for symmetrical faces appears to be affected by fertility in women. One limitation of previous research is that faces are often symmetrically lit frontviews and so symmetry can be assessed using 2D pictorial information. Another limitation is that two-alternative-forced-choice (2afc) tasks are often used to assess symmetry preference and these cannot distinguish between differences in preference for symmetry and differences in ability of asymmetry detection. The current study used three tasks to assess the effects of facial symmetry: attractiveness ratings, 2afc preference and asymmetry detection. To break the link between 2D pictorial symmetry and facial symmetry, 3D computer generated heads were used with asymmetrical lighting and yaw rotation. Facial symmetry correlated with attractiveness even under more naturalistic viewing conditions. Path analysis indicates that the link between fertility and 2afc symmetry preference is mediated by asymmetry detection not increased preference for symmetry. The existing literature on symmetry preference and attractiveness is reinterpreted in terms of differences in asymmetry detection

Attention and Decision-making: How allocation of attention to decision alternatives influences the final choice

Research in the area of decision-making has acknowledged the role of attention in arriving to the final choice. The gaze cascade model suggests a bidirectional relationship between attention and preference – as we begin to orient towards the preferred option, such orienting further increases preference. The attentional drift diffusion model suggests that attention can amplify evidence; however, attention varies randomly between the options. This thesis aims to investigate the role of attention in decision-making from two perspectives: the decision-making models that suggest that attention can bias evidence, and the perceptual learning literature, which has investigated how exposure can affect discrimination between similar stimuli. Chapter 1 investigates whether attention can bias preference. We used a design in which some of the decision options are paired with reward-related stimuli. As we expected such stimuli to capture attention, we aimed to investigate whether such attentional capture can bias the choice. Our results showed a choice bias over short exposure times but not with self-paced decisions. Chapter 2 investigates whether attention is biased towards the eventually chosen option. Using a perceptual decision task, results showed that participants spend longer attending to the chosen option; however, the result did not replicate when the task required participants to press a key to inspect each option. Chapters 3 and 4 investigate the intermixed-blocked exposure effect, a finding that shows how the manner of exposure to stimuli can affect the ease of discrimination between them. Specifically, alternating exposure to two stimuli facilitates discrimination relative to a case in which all exposures to one precede all exposures to the other. Chapter 3 investigates the inhibitory relationships account, which suggests that alternating exposure to stimuli allows for inhibitory relationships to form between their unique features, such that the presence of one signals the absence of the other. However, our experiments showed no evidence for this account. Chapter 4 investigates a memory account of the intermixed-blocked exposure effect - the account suggests that alternating exposure between two stimuli means that the unique feature of each, shown at every other exposure, requires more processing than the rest of the stimulus. However, our results showed that increasing the delay between exposures to the unique features had no effect on discrimination accuracy

Effet du son dans les vidéos sur la direction du regard (contribution à la modélisation de la saillance audiovisuelle)

Les humains reçoivent grande quantité d'informations de l'environnement avec vue et l'ouïe . Pour nous aider à réagir rapidement et correctement, il existe des mécanismes dans le cerveau à l'attention de polarisation vers des régions particulières , à savoir les régions saillants . Ce biais attentionnel n'est pas seulement influencée par la vision , mais aussi influencée par l'interaction audio - visuelle . Selon la littérature existante , l'attention visuelle peut être étudié à mouvements oculaires , mais l'effet sonore sur le mouvement des yeux dans les vidéos est peu connue . L'objectif de cette thèse est d'étudier l'influence du son dans les vidéos sur le mouvement des yeux et de proposer un modèle de saillance audio - visuel pour prédire les régions saillants dans les vidéos avec plus de précision . A cet effet, nous avons conçu une première expérience audio - visuelle de poursuite oculaire . Nous avons créé une base de données d'extraits vidéo courts choisis dans divers films . Ces extraits ont été consultés par les participants , soit avec leur bande originale (condition AV ) , ou sans bande sonore ( état V) . Nous avons analysé la différence de positions de l'oeil entre les participants des conditions de AV et V . Les résultats montrent qu'il n'existe un effet du bruit sur le mouvement des yeux et l'effet est plus important pour la classe de la parole à l'écran . Ensuite , nous avons conçu une deuxième expérience audiovisuelle avec treize classes de sons. En comparant la différence de positions de l'oeil entre les participants des conditions de AV et V , nous concluons que l'effet du son est différente selon le type de son , et les classes avec la voix humaine ( c'est à dire les classes parole , chanteur , bruit humain et chanteurs ) ont le plus grand effet . Plus précisément , la source sonore a attiré considérablement la position des yeux uniquement lorsque le son a été la voix humaine . En outre , les participants atteints de la maladie de AV avaient une durée moyenne plus courte de fixation que de l'état de V . Enfin , nous avons proposé un modèle de saillance audio- visuel préliminaire sur la base des résultats des expériences ci-dessus . Dans ce modèle , deux stratégies de fusion de l'information audio et visuelle ont été décrits: l'un pour la classe de son discours , et l'autre pour la musique classe de son instrument . Les stratégies de fusion audio - visuelle définies dans le modèle améliore la prévisibilité à la condition AVHumans receive large quantity of information from the environment with sight and hearing. To help us to react rapidly and properly, there exist mechanisms in the brain to bias attention towards particular regions, namely the salient regions. This attentional bias is not only influenced by vision, but also influenced by audio-visual interaction. According to existing literature, the visual attention can be studied towards eye movements, however the sound effect on eye movement in videos is little known. The aim of this thesis is to investigate the influence of sound in videos on eye movement and to propose an audio-visual saliency model to predict salient regions in videos more accurately. For this purpose, we designed a first audio-visual experiment of eye tracking. We created a database of short video excerpts selected from various films. These excerpts were viewed by participants either with their original soundtrack (AV condition), or without soundtrack (V condition). We analyzed the difference of eye positions between participants with AV and V conditions. The results show that there does exist an effect of sound on eye movement and the effect is greater for the on-screen speech class. Then, we designed a second audio-visual experiment with thirteen classes of sound. Through comparing the difference of eye positions between participants with AV and V conditions, we conclude that the effect of sound is different depending on the type of sound, and the classes with human voice (i.e. speech, singer, human noise and singers classes) have the greatest effect. More precisely, sound source significantly attracted eye position only when the sound was human voice. Moreover, participants with AV condition had a shorter average duration of fixation than with V condition. Finally, we proposed a preliminary audio-visual saliency model based on the findings of the above experiments. In this model, two fusion strategies of audio and visual information were described: one for speech sound class, and one for musical instrument sound class. The audio-visual fusion strategies defined in the model improves its predictability with AV condition.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Perception of facial asymmetries in two and three dimensions

Gesichter mit ausgeprägten Asymmetrien werden häufig als unattraktiv empfunden, allerdings können geringe Asymmetrien die Attraktivität eines Gesichtes auch steigern. Ziel der vorliegenden Untersuchung war es, zu quantifizieren ab wann Abweichungen auffallen und als unattraktiv empfunden werden. Dazu wurden die mit einem optischen 3D-Sensor erhobenen Gesichtdaten eines symmetrischen Patienten im Bereich von Nase, Lippen und Kinn graduell (in 2mm-Schritten) verändert. Die Beurteilung der Gesichter wurde durch jeweils 30 Kieferorthopäden, Mund-, Kiefer- und Gesichtschirurgen und Laien vorgenommen. Im ersten Teil wurde anhand von sechsstufigen Skalen die Symmetrie bewertet, im zweiten Teil anhand von Paarvergleichen die Attraktivität. Hierzu wurden die Gesichter zum Einen als Enface-Bild und zum Anderen bewegt als Video präsentiert. Es konnten sowohl Asymmetrieformen identifiziert werden, die als besonders unattraktiv empfunden wurden, als auch Schwellenwerte für die individuelle Wahrnehmung der verschiedenen Asymmetrien bei den jeweiligen Probandengruppen. Diese Untersuchung liefert somit Zusatzinformationen für die Beurteilung von Gesichtsasymmetrien.Faces with distingtive asymmetries are often seen as unattractive. However minor asymmetries can enhance facial attractiveness. The purpose of this study was to quantify when abnormalities of facial symmetry are in evidence and are seen as unattractive. For this purpose facial data of a symmetric adult male patient were aquired with an optical 3D sensor. Virtual faces were created through gradual alteration of the nose, the lips and the philtrum. The virtual faces were evaluated in groups of 30 orthodontists, 30 craniofacial surgeons and 30 lay people. In the first part of this study the symmetry of the faces were evaluated based on a rating scale (1 to 6). In the second part of this study the evaluators compaired pairs and decided which face is more attractive. In both parts the faces were shown both in a two and three dimensional presentation. The results showed that there are facial asymmetries that are classified as more unattractive than others and that the extent of asymmetry also is very important in the ranking of facial attractiveness. This study shows a lot of information for the evaluation of facial asymmetries