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 (Macaca fuscata). 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.