Affective bodily responses in monkeys predict subsequent pessimism, but not vice versa

Affect is a complex interplay of behaviour, physiology, cognition and subjective feelings. The James-Lange theory, which posits that affective bodily responses occur first and subsequently shape our affective experiences, has been extensively studied in humans but remains underexplored in non-human animals. This study employs a judgement bias test to explore the relationship between peripheral bodily responses, specifically self-scratching associated with negative affect, and shifts in cognitive information-processing modes (i.e. a 'pessimistic' judgement bias characterized by heightened anticipation of undesirable outcomes) in Japanese macaques (<i>Macaca fuscata</i>). Our findings support the hypothesis that bodily responses precede and influence changes in cognitive modes, demonstrating that self-scratching predicts subsequent pessimistic judgements, but not vice versa. This study provides comparative insights into the biological underpinnings of affect, highlighting that peripheral behaviours can shape cognitive processes in non-human primates. These results have broader implications for understanding the evolutionary continuity and adaptive significance of affective response systems across species.