Background: Accumulating studies document changes in the perception of and response to socially mediated information, such as facial expressions, with administration of oxytocin. Across studies, however, its effects on emotion perception have been inconsistent. Outside the laboratory, affective judgments about another person (e.g., Is that person angry at me?) involve interpretation of perceptual uncertainty (e.g., scowls do not always indicate anger) and assessment of behavioral risk (e.g., the costs of inferring anger when it does not exist differ from the costs of missing anger when it does exist). An account of these decision variables is missing from studies of the effects of oxytocin on emotion perception. To characterize oxytocin’s effects on emotion perception from a decision-making perspective, we utilized a task that combines perceptual uncertainty with behavioral economics in a signal detection framework. We used the probability of encountering angry faces and the cost of misidentifying them as not angry (risk) to create a biased (biased towards reporting anger when not sure) perceptual environment. We measured the effect of oxytocin on perceivers’ ability to achieve optimal bias in this environment. Based on prior data suggesting that oxytocin attenuates risk aversion, we hypothesized that receiving oxytocin would result in insufficient bias, due to under-estimating the probability of encountering angry faces and/or to under-valuing the cost of mistakes relative to placebo. Methods: Forty psychotropic-free healthy control participants (age: M=44.0 ± 10.32 [SD] years, 45% women) participated in a randomized double-blind administration of intranasal oxytocin or placebo prior to computer based tasks at the Center for Anxiety and Traumatic Stress Disorders (CATSD) at Massachusetts General Hospital. All were free of psychiatric disorders, per clinical interview with the Structured Clinical Interview for DSM-IV. Participants were given 30 IU of double-blind intranasal oxytocin (Syntocinon®, Novartis) or placebo (oxytocin: n=22, 9 women; placebo: n=18, 7 women) thirty minutes before the computer tasks. In this signal detection framework, faces that depicted expressions ranging from relaxed to strongly scowling comprised two categories: “angry” (targets) and “not angry” (foils). Uncertainty was implemented by creating distributions of targets and foils which shared exemplars (i.e., the distributions overlapped on the perceptual domain: targets were M = 60 ± 15% (1 SD) scowl intensity, foils were M = 40 ± 15% (1 SD) scowl intensity). Risk was created by earning or losing points for correct vs. incorrect categorization of targets and foils (i.e., categorizing a target as “not angry” cost more points than categorizing a foil as “angry”). Additionally, the base rate of targets was 0.6 (60% of trials were targets). The combination of relatively high missed detection cost and relatively frequent targets dictated a liberal optimal bias: a tendency to categorize faces as angry was required to maximize points earned. Over 230 trials, participants attempted to optimize their categorization of the faces, answering the on-screen prompt “Is this person angry?”. Participants received immediate on-screen feedback (“Yes – that was right” or “No – that was wrong”, points earned for the current trial, and cumulative points earned). Results: Controlling for baseline perceived stress (Perceived Stress Scale) and trait anxiety (State Trait Anxiety Index, Trait Total Score) in this non-psychiatrically ill sample, we found a significant interaction of drug and gender on response bias (ANCOVA, F(1,32)=4.1, p<0.049), without main effects. Men who received oxytocin exhibited a significantly less liberal (less optimal, based on experimental parameters) bias for perception of anger in faces than those who received placebo (follow-up ANCOVA among men, F(1,20)=5.0, p<0.037). In contrast, women's bias was not significantly affected by oxytocin (follow-up ANCOVA among women, F(1,12)=0.6, p>0.4). Discussion: Participants attempted to optimize their judgments about angriness depicted in facial expressions, in the context of experimenter-defined values of target-foil perceptual similarity, payoffs (points earned/lost), and “anger” base rate. Men given oxytocin appeared less able to calibrate their emotion perception to the signal detection parameters that cause bias (payoffs, base rate, or both). As a learning experiment, our results suggest that oxytocin may impair men’s ability to optimally adapt emotion perception (e.g., judgments of angriness from faces) to differences in risk and uncertainty that characterize different social contexts, while there was no effect of oxytocin for women. These data suggest that oxytocin might reduce (normalize) over-estimates of the base rate of threat or reduce (normalize) over-estimates of the magnitude of punishments that otherwise might contribute to excessive social withdrawal or reduced social approach behaviors. We cannot rule out, however, that by reducing the salience of risk, oxytocin treatment in men could potentially promote risk-prone decision-making in domains outside a patient’s core symptomatology. More research is needed to understand the potential role and possible side effects of oxytocin in interventions.
Simon, N. M., Lynn, S. K., Hoge, E. A., Fischer, L. E., and Barrett, L. F. 2012. Oxytocin influences response bias in men but not women in a signal detection emotion perception task. 51st Annual Meeting of the American College of Neuropsychopharacology, December 2-6, 2012, Hollywood Florida.
These data also presented at CNS 2013.
