Eye contact with neutral and smiling faces: effects on autonomic responses and frontal EEG asymmetry

Abstract

In our previous studies we have shown that seeing another person "live" with a direct vs. averted gaze results in enhanced skin conductance responses (SCRs) indicating autonomic arousal and in greater relative left-sided frontal activity in the electroencephalography (asymmetry in the alpha-band power), associated with approach motivation. In our studies, however, the stimulus persons had a neutral expression. In real-life social interaction, eye contact is often associated with a smile, which is another signal of the sender's approach-related motivation. A smile could, therefore, enhance the affective-motivational responses to eye contact. In the present study, we investigated whether the facial expression (neutral vs. social smile) would modulate autonomic arousal and frontal EEG alpha-band asymmetry to seeing a direct vs. an averted gaze in faces presented "live" through a liquid crystal (LC) shutter. The results showed that the SCRs were greater for the direct than the averted gaze and that the effect of gaze direction was more pronounced for a smiling than a neutral face. However, in this study, gaze direction and facial expression did not affect the frontal EEG asymmetry, although, for gaze direction, we found a marginally significant correlation between the degree of an overall bias for asymmetric frontal activity and the degree to which direct gaze elicited stronger left-sided frontal activity than did averted gaze.

Keywords: electroencephalography; facial expression; gaze direction; motivation; skin conductance response; social cognition.

Figure 1

A stimulus model with direct and averted gaze having a smiling (above) and a neutral expression (below).

Figure 2

Mean skin conductance responses (square root-transformed SCRs in μMho) as a function facial expression and gaze direction.

Figure 3

A scatter plot with a linear fit curve for the participant's overall asymmetry score in the EEG alpha power (in ln-transformed μV²/Hz between electrodes F4 and F3) averaged across all experimental conditions (X-axis; asyscore_overall,) vs. the difference in asymmetry scores for direct and averted gaze (Y-axis; asyscore_direct – asyscore_averted). For X-axis scores, negative values indicate right-sided asymmetry (associated with avoidance) and positive values indicate left-sided asymmetry (associated with approach). For Y-axis scores, negative values indicate stronger avoidance-related brain activity for direct vs. averted gaze, whereas positive values indicate stronger approach-related brain activity for direct vs. averted gaze.