Sex Differences in Affective Processing Taking a Comparative & Evolutionary Approach

No Thumbnail Available
Journal Title
Journal ISSN
Volume Title
Across domains ranging from clinical to evolutionary psychology, and well engrained in the public’s perception, is the idea that women are the more emotional sex in comparison to men. However, the extent to which perceived sex differences are real and rooted in biology (and therefore evolutionary processes) and not the result of social factors is not entirely clear. In order to investigate whether sex differences in affective processing are rooted in biology, we adopted an evolutionary and comparative approach and studied 7 male and 7 female rhesus macaques (Macaca mulatta) in 4 different experiments that used behavioral, physiological and attentional measures to quantify sex differences in affective processing. We did not observe sex differences in the majority of our experiments – including experiments that measured affective reactivity to threatening humans (Experiment 1) and live animal stimuli (Experiment 2) and an experiment that measured monkeys’ toy preference (Experiment 3). We did observe some sex differences in an experiment that measured autonomic nervous system activity and visual attention to passively viewed movies that varied in affective content (Experiment 4) – we observed that in comparison to females, males has significantly higher Respiratory Sinus Arrhythmia values, a measure that reflects parasympathetic nervous system activity, and attended movies that showed neutral affective content significantly more than females. We did not observe any sex differences in measures that reflected sympathetic nervous system activity (i.e., Dark-Adapted Pupil Diameter) or in measures that reflected mixed parasympathetic and sympathetic nervous system activity (i.e., heart rate and respiration rate). These results suggest that males overall were less engaged with the movie stimuli compared to females and were possibly less anxious compared to females. Our findings are not in line with results from human studies, which generally do not report sex differences physiological measures relating to affective processing. This could mean that human sex differences are largely the result of social and cultural processes and are not rooted in biology. However, to our knowledge we are the first ones to study sex differences in rhesus macaques across tasks using various measures for affective processing, and more research using a wider variety of animal models and translational tools is warranted.
Faculteit der Sociale Wetenschappen