Table 2.

Definitions of eye-tracking variables

Variable	Variable definition
Standard gaze variables
(1) Dwell time*	Percentage of looking time (sec) toward an AOI was derived by summing the fixation duration of each AOI and dividing it by the total duration of looking, multiplied by 100
(2) Fixation count*	Percentage of the number of fixations was captured by summing the total number of fixations toward an AOI out of the total number of fixations across the duration of stimulus presentation, multiplied by 100
Temporal dynamics
(3) Percentage of fixations over time	Growth curve analyses (GCA) were employed to investigate change in looking patterns (percentage of fixations) over the course of the stimulus towards social versus non-social AOIs. To account for track loss at the beginning and end of the stimulus presentation, 7 s of the 8 s image were examined (500 ms removed from the beginning and end of the stimuli), using 1 s time bins. Follow-up analyses examined the divergence between groups of social versus non-social looking using t-tests with 300 ms time bins
Fixation patterns
(4) Perseverative fixations*	Percentage of perseverative fixations were derived by summing fixations that occurred in succession toward the same AOI, divided by the total number of fixations, multiplied by 100
(5) Regressive fixations*	Percentage of regressive fixations was captured as the percentage of times a participant returned their gaze to a specific AOI that had already been previously explored, by summing the number of fixations that occurred towards an AOI previously fixated (not including successive fixations/perseverative fixations), divided by the total number of fixations, multiplied by 100
(6) Fixation transition analysis*	Transitions between social and non-social information were explored in four ways: (i) social to social AOI transitions, (ii) non-social to non-social AOI transitions, (iii) social to non-social AOI transitions, (iv) non-social to social AOI transitions, and (v) total transitions between social and non-social AOIs. Percentages based on the total number of transitions information were calculated for (i)–iv)
First fixations
(7) First fixation AOI	The percentage of first fixations toward social or non-social information was measured by summing the total number of first fixations that was social or non-social and dividing it by the total number of first fixations, multiplied by 100
(8) First fixation duration*	The first fixation duration was derived by measuring the time (in sec) spent examining any AOI during the first fixation (i.e., the first fixation that occurs after the stimulus appears) before making a fixation transition
Distribution patterns
(9) Fixation rate (exploration)*	The total number of fixations per participant was divided by the total time spent examining the scene, to produce the number of fixations that occurred per second of track time regardless of AOI
(10) Fixation rate (exploration) AOI*	The number of fixations per track time (in sec) toward social or non-social information was calculated
(11) Fixation spatial distribution/coverage*	First, a 5 × 4 matrix of 20 large areas (256 × 256 pixels / 6.45° × 6.45°) and a 10 × 8 matrix of 80 small areas (128 × 128 pixels / 3.2° × 3.2°) were generated. Each fixation point’s location was categorized into one of these 20 or 80 “boxes”, respectively. To account for the different number of fixations per participant, the percentage of mini areas explored was computed per participant by taking the number of areas explored and dividing it by the total number of fixations for that participant, which was then multiplied by 100. This final percent coverage was included in subsequent analyses for larger (5 × 4 matrix) and smaller (10 × 8 matrix) areas

*Variables included in the principal component analysis