Development of ambiguity processing is explained by an inverted U-shaped curve

Background: Understanding the developmental trajectories for recognizing facial expressions is important for a better understanding of psychopathology development. In this study, we examined the recognition of emotional and neutral facial expressions in typically developing adolescents and adults.Methods: We used the Emotion Intensity Rating task to examine recognition of facial expressions in 93 individuals (35 adolescents (12-18 years old), 58 adults (18-45 years old) without a history of psychiatric or systemic disorders. Participants rated the intensity of emotional expression in happy, neutral, and sad faces on a scale of 1 to 9 with a score ‘5’ assigned to neutral faces, scores between ‘6’ (slightly happy) and ‘9’ (very happy) assigned to happy faces, and scores between ‘4’ (slightly sad) and ‘1’ (very sad) assigned to sad faces. Mixed effects models examined the effects of age and emotions on recognition accuracy, reaction time (RT), and emotion intensity. Results: Participants tended to misjudge neutral faces as sad. Recognition of happy and sad faces was similar in adolescents and adults. Adolescents were less accurate than adults for neutral face recognition (p<0.01). There was a significant quadratic effect of age on accuracy and RT with most accurate and fastest performance observed in 25-35 year-olds. Conclusion: The ability to recognize ambiguous neutral facial expressions develops during adolescence, follows an inverted U-shaped trajectory, and peaks in early adulthood. This trajectory may be associated with the prefrontal cortex maturation that provides top-down control over the heightened amygdala response to ambiguity that may be misinterpreted as emotional content.