Relative area normed fixation density of the first three fixations after stimulus onset (before response) on the different regions of interest for all tasks separately.

<p>Top row: first fixations for social stimuli on four regions of interest (head, body, areas of low saliency and high saliency), bottom row: first fixations for non-social stimuli on two regions of interest (areas of low and high saliency). Error bars indicate standard errors of the mean.</p

Direct comparison of relative area normed fixation density for social (above) and non-social stimuli (below) on different regions of interest for two different time windows (before and after a given response) as a function of task.

<p>The time window before the mouse click is referred to as “task relevant” (left panels), as it reflects possible top-down strategies on viewing behavior that were induced by the explicit tasks. The time window after completing the task is termed “task irrelevant” (right panels), as attentional allocation in this period should be less governed by task instructions. As there was no postulated task for the free-viewing condition, the task irrelevant time window does not contain any data for this modality. Viewing behavior for non-social stimuli was analyzed without social regions of interest, but allowed for comparing relative area normed fixation densities for areas of low and high saliency. Error bars indicate standard errors of the mean.</p

The graph depicts the mean saliency values for the different regions of interest (head, body, areas of low and high saliency) for all social images according to the graph-based visual saliency algorithm [4].

<p>The values depicted within the bars describe the mean number of ROIs per category and image across all social stimuli. Error bars represent standard errors of the mean.</p

Saccade proportions.

<p>(A) Proportion of successful saccades (terminating in the quadrant in which social features were displayed). Here, proportions were calculated for all trials in which social features appeared in one of the four quadrants (LL = lower left, UL = upper left, LR = lower right, UR = upper right). Each circled dot represents one participant. Dark red dots denote the mean proportion of all participants and error bars depict the standard error of the mean. (B) Proportion of saccades terminating in one of the four quadrants (LL = lower left, UL = upper left, LR = lower right, UR = upper right) for all social scenes.</p

Heat maps illustrating the normalized fixation time on different face regions for the long presentation time of Experiment 1 (A) and the normalized distribution of saliency (B) as derived from a computational model of bottom-up visual attention [<b>13</b>], [<b>14</b>] for fearful, happy and neutral facial expressions.

<p>Heat maps illustrating the normalized fixation time on different face regions for the long presentation time of Experiment 1 (A) and the normalized distribution of saliency (B) as derived from a computational model of bottom-up visual attention <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041792#pone.0041792-Itti1" target="_blank">[<b>13</b>]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041792#pone.0041792-Itti2" target="_blank">[<b>14</b>]</a> for fearful, happy and neutral facial expressions.</p

Frequency histograms showing the distribution of saliency ratios (average saliency in the eye region divided by the average saliency in the mouth region) for fearful, happy and neutral facial expressions.

<p>Frequency histograms showing the distribution of saliency ratios (average saliency in the eye region divided by the average saliency in the mouth region) for fearful, happy and neutral facial expressions.</p

Proportion of time spent fixating either the eye or the mouth region in relation to the time subjects spent fixating the overall face (Experiment 2).

<p>Mean proportions for fixations on the eye or mouth region are shown as a function of the position in the visual field and the facial expression. Results are depicted separately for a stimulus set with a similar saliency ratio of the eye as compared to the mouth region across facial expressions (stimulus set 1) and for a stimulus set with a saliency ratio of approximately 1 (stimulus set 2). The regions of interest that were used to define fixations in the eye or mouth region, respectively, are shown on the right side. Error bars indicate standard errors of the mean.</p

Trial procedure and example stimuli.

<p>A) Trial procedure. B) Example image, not included in the original dataset but taken post-hoc, illustrating how stimuli were cropped and mirrored such that social features were being restricted to a different quadrant in each version. The individual depicted in this figure has given written informed consent (as outlined in PLOS consent form) to publish these case details.</p

Proportions of fixation changes towards the eye and the mouth region as a function of the position in the visual field and the facial expression (Experiment 2).

<p>Results are depicted separately for a stimulus set with a similar saliency ratio of the eye as compared to the mouth region across facial expressions (stimulus set 1) and for a stimulus set with a saliency ratio of approximately 1 (stimulus set 2). The regions of interest that were used to define whether saccades targeted the eye or mouth region, respectively, are shown on the right side. Error bars indicate standard errors of the mean.</p

Experiment 2: Proportions of correct responses in the emotion classification task as a function of vertical placement and emotional expression.

<p><i>Note</i>. Standard errors of the mean are printed in brackets.</p