Visual preferences for direct-gaze faces in infant macaques (Macaca mulatta) with limited face exposure

Abstract

From birth, human and nonhuman primates attend more to faces with direct gaze compared with averted gaze, and previous studies report that attention to the eyes is linked to the emergence of later social skills. Here, we explored whether early experiences influence attraction to eye contact in infant macaques by examining their attention to face pairs varying in their gaze direction across the first 13 weeks of life. Infants raised by human caretakers had limited conspecific interactions (nursery-reared; N = 16) and were compared to infants raised in rich social environments (mother-reared; N = 20). Both groups looked longer to faces and the eyes of direct compared to averted-gaze faces. Looking to all faces and eyes also increased with age. Nursery-reared infants did not display age-associated increases in attention to direct-gaze faces specifically, suggesting that, while there may be an initial preference for direct-gaze faces from birth, social experiences may support its early development.

Keywords: attention; infant development; mutual gaze; primate; social attention; vision.

Figure 1.

Direct gaze (top left) and averted gaze (top right) sample stimuli. Areas of interest (AOI) are shown around the head and eye zone regions (bottom).

Figure 2.

Overall fixation proportion collapsed across age in nursery-reared infants. Infants looked for a greater proportion of time to the direct (dark blue) compared to averted (light blue) gaze faces, for both the face region (left plot) and eye region (right plot), ps < .05. Solid horizontal lines indicate medians, the bottom and top of the boxes indicate 25th and 75th percentiles, respectively, and whiskers indicate the most extreme data point that is no more than 1.5 × interquartile range (IQR) below the lower quartile and above the upper quartile. Dots indicate outliers, more than 1.5 × IQR.

Figure 3.

Fixation proportion across development (in weeks) in mother-reared (left graphs) and nursery-reared (right graphs) infants. Infants displayed increases in their proportions of time looking to the areas of interest (AOI) in the zones around the face (top graphs) and eyes (bottom graphs) with age, ps < .05. Direct-gaze faces are represented with dark blue and averted-gaze faces are represented with light blue. Points reflect means and error bars reflect standard errors of the means.

Figure 4.

Mean fixation proportion collapsed across age in mother-reared (left graph) and nursery-reared (right graph) infants, for the areas of interest (AOI) in the zones around the face and eyes, for direct-gaze (dark blue) and averted-gaze (light blue) faces. There was a stimulus type × rearing interaction for the face looking time proportion, ps < .05, indicating that mother-reared infants displayed a larger difference in attention between direct and averted gaze faces compared to nursery-reared infants. Error bars reflect standard error of the mean.