Previous studies have documented atypicalities in processing facial expressions of emotion in children and adults with autism spectrum disorders (ASD). Because these atypicalities are seen in both affected and unaffected family members, they may be considered an endophenotype of ASD, reflecting a genetically-mediated risk factor for the disorder.
Objectives: To study the development of this potential endophenotypic marker, we investigated looking preferences to facial expressions of emotion in 8-month-old infant siblings of children with ASD (“High-Risk” infants) in comparison to infants from families without autism history (“Low-Risk” infants).
Methods: Data from 38 Low-Risk (15F, 23M) and 16 High-Risk (5F, 11M) infants contributed to this study. Forced-Choice Preferential Looking was used to measure infants’ preferences to black and white pictures of “Disgust”, “Happy” and “Neutral” faces (obtained from www.macbrain.org). Each infant was tested with three different pairings: 1) Disgust vs. Neutral, 2) Happy vs. Neutral, and 3) Happy vs. Disgust. On each trial, one of the three pairings was presented, with one emotion presented on the left, and one on the right, side of the video monitor. The left/right position and the emotional pairing were randomized across trials. After each trial, the experimenter (blind to the monitor) judged which side (left or right) the infant preferred to look at. Six different faces were employed, with the gender of the face (Face-Gender) being split (3 Female, 3 Male). Within a condition, values greater than 50% indicate a preference for one emotion over another. Two-factor ANOVAs (Subject Group x Face-Gender) allowed us to look for overall group differences, effects of Face-Gender of emotional preferences, and the interaction between the two.
Results: For Disgust vs. Neutral, both groups showed a preference for Disgust (Low-Risk: 56.1%, p = 0.0001, High-Risk: 59.3%, p = 0.001), but there was no group difference. There was, however, a significant interaction between Subject Group x Face-Gender (p = 0.04), which was driven by a significant Face-Gender effect in High-Risk infants (p = 0.01), but not in Low-Risk infants. Specifically, for High-Risk infants, the Disgust preference was significantly greater for Female faces (66.4%) than Male faces, (52.2%). And, for Female faces, the Disgust preference was significantly greater in High-Risk than Low-Risk infants (p = 0.01). Interestingly, for Happy vs. Neutral, both groups showed a preference for Happy, but only for Male faces (Low-Risk: 54.0%, p = 0.05, High-Risk: 59.4%, p = 0.03). Neither group showed significant preferences for Disgust vs. Happy, presumably because the two emotions are equally salient.
These preliminary behavioral data suggest larger Face-Gender effects on emotional face processing in High-Risk infants. Specifically, for Female faces, High-Risk infants exhibit an exaggerated preference for Disgust. This could arise either from fundamental differences in emotional processing (e.g., greater amygdala responses to negative emotions) or atypical experience with disgusted faces (e.g., perhaps disgusted female faces are more novel in their environment). Either way, such differences could provide a potential endophenotypic marker associated with ASD.