Nathalie Guyader

Dr. Nathalie Guyader


Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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26 June 2014 in Journal of Vision
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ACAntoine Coutrot
Antoine Coutrot
NGNathalie Guyader
Nathalie Guyader
Conversation scenes are a typical example in which classical models of visual attention dramatically fail to predict eye positions. Indeed, these models rarely consider faces as particular gaze attractors and never take into account the important auditory information that always accompanies dynamic social scenes. We recorded the eye movements of participants viewing dynamic conversations taking place in various contexts. Conversations were seen either with their original soundtracks or with unrelated soundtracks (unrelated speech and abrupt or continuous natural sounds). First, we analyze how auditory conditions influence the eye movement parameters of participants. Then, we model the probability distribution of eye positions across each video frame with a statistical method (Expectation-Maximization), allowing the relative contribution of different visual features such as static low-level visual saliency (based on luminance contrast), dynamic low-level visual saliency (based on motion amplitude), faces, and center bias to be quantified. Through experimental and modeling results, we show that regardless of the auditory condition, participants look more at faces, and especially at talking faces. Hearing the original soundtrack makes participants follow the speech turn-taking more closely. However, we do not find any difference between the different types of unrelated soundtracks. These eye-tracking results are confirmed by our model that shows that faces, and particularly talking faces, are the features that best explain the gazes recorded, especially in the original soundtrack condition. Low-level saliency is not a relevant feature to explain eye positions made on social scenes, even dynamic ones. Finally, we propose groundwork for an audiovisual saliency model.

1 September 2015 in Journal of Vision
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HDHélène Devillez
Hélène Devillez
NGNathalie Guyader
Nathalie Guyader
AGAnne Guérin-Dugué
Anne Guérin-Dugué
The P300 event-related potential has been extensively studied in electroencephalography with classical paradigms that force observers to not move their eyes. This potential is classically used to infer whether a target or a task-relevant stimulus was presented. Few researches have studied this potential through more ecological paradigms where observers were able to move their eyes. In this study, we examined with an ecological paradigm and an adapted methodology the P300 potential using a visual search task that involves eye movements to actively explore natural scenes and during which eye movements and electroencephalographic activity were coregistered. Averaging the electroencephalography signal time-locked to fixation onsets, a P300 potential was observed for fixations onto the target object but not for other fixations recorded for the same visual search or for fixations recorded during the free viewing without any task. Our approach consists of using control experimental conditions with similar eye movements to ensure that the P300 potential was attributable to the fact that the observer gazed at the target rather than to other factors such as eye movement pattern (the size of the previous saccade) or the “overlap issue” between the potentials elicited by two successive fixations. We also proposed to model the time overlap issue of the potentials elicited by consecutive fixations with various durations. Our results show that the P300 potential can be studied in ecological situations without any constraint on the type of visual exploration, with some precautions in the interpretation of results due to the overlap issue.

1 June 2012 in Cognitive Computation
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SMSophie Marat
Sophie Marat
ARAnis Rahman
Anis Rahman
DPDenis Pellerin
Denis Pellerin
NGNathalie Guyader
Nathalie Guyader
DHDominique Houzet
Dominique Houzet

1 February 2012 in Journal of Vision
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THTien Ho-Phuoc
Tien Ho-Phuoc
NGNathalie Guyader
Nathalie Guyader
FLFrédéric Landragin
Frédéric Landragin
AGAnne Guérin-Dugué
Anne Guérin-Dugué
Since Treisman's theory, it has been generally accepted that color is an elementary feature that guides eye movements when looking at natural scenes. Hence, most computational models of visual attention predict eye movements using color as an important visual feature. In this paper, using experimental data, we show that color does not affect where observers look when viewing natural scene images. Neither colors nor abnormal colors modify observers' fixation locations when compared to the same scenes in grayscale. In the same way, we did not find any significant difference between the scanpaths under grayscale, color, or abnormal color viewing conditions. However, we observed a decrease in fixation duration for color and abnormal color, and this was particularly true at the beginning of scene exploration. Finally, we found that abnormal color modifies saccade amplitude distribution.

1 April 2017 in Vision Research
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Journal Article
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NGNathalie Guyader
Nathalie Guyader
ACAlan Chauvin
Alan Chauvin
MBMuriel Boucart
Muriel Boucart
CPCarole Peyrin
Carole Peyrin

27 June 2010 in Journal of Real-Time Image Processing
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ARAnis Rahman
Anis Rahman
DHD. Houzet
D. Houzet
DPD. Pellerin
D. Pellerin
SMS. Marat
S. Marat
NGNathalie Guyader
Nathalie Guyader