Intranasal oxytocin does not alter initial perceptions of facial trustworthiness in younger or older adults

Background: Oxytocin is a neuropeptide involved in a range of social processes, and prior research has shown that intranasal oxytocin (iOT) may enhance trusting behaviors. However, it is unclear whether iOT influences perceptions of whether a face is trustworthy. In addition, no studies in this literature have investigated whether the participant's age may play a moderating role in the effects of iOT on trust. Aims: We aimed to examine for the first time whether iOT influences perceptions of facial trustworthiness and eye-gaze patterns and, if so, whether age moderates these iOT effects. Methods: One hundred and eighteen participants took part in a randomized, double-blind, placebo-controlled, within-groups study. Participants made judgments about the perceived trustworthiness of a series of faces while their eye movements were monitored. Results: Younger and older adults differed in their judgments of facial trustworthiness. However, most critically, iOT had no effect on these judgments for either age group. For the eye-tracking data, prior age effects in attending to the stimuli were replicated, with older adults gazing less at the eye region and more at the mouth region relative to younger adults. However, iOT had no effect on eye gaze. Conclusions: These findings are discussed in relation to the growing body of literature that suggests that the effect of iOT on social processing is complex and may not be as robust as first thought.