Monkey See, Monkey Feel: How Stress Shapes Decision-Making

Have you ever wondered how our emotions and body responses are connected and if other animals respond in the same way? A fascinating new study from Kyoto University, published in Proceedings of the Royal Society B, explores this link in Japanese macaques. The researchers discovered that bodily responses—like self-scratching, a behavior tied to anxiety—can predict pessimistic decision-making in monkeys. However, the reverse isn’t true (i.e., cognitive pessimism doesn’t seem to trigger bodily responses). 

This finding sheds light on the evolutionary roots of emotion and cognition.Using a clever setup, the researchers presented six macaques with buttons representing positive, negative, and ambiguous outcomes. They paired this with video analysis of self-scratching behavior. Monkeys were more likely to avoid the ambiguous button (a sign of pessimism) right after scratching themselves. Interestingly, this contrasts with humans, where negative thinking can often lead to physical signs of stress. This suggests that in macaques, bodily responses may drive cognitive shifts rather than the other way around.

So why is this observation important to us? For one, it helps us understand how emotions evolved. The study hints that emotional bodily responses might have been an ancient survival mechanism—helping animals respond quickly to threats before engaging in complex thought. This could explain why such mechanisms are conserved across species. Moreover, it raises intriguing questions about how human emotional systems diverged from that of other primates due to the emergence of our unique language and introspection abilities.

This line of research also has some interesting implications for understanding mental health in a cross species perspective. For instance, by studying how bodily responses influence cognition in animals, we can uncover new ways to address anxiety and mood disorders in humans but the promise of this work really lies in the ability to expand these observations to other species. For instance, in humans we have developed a comprehensive guide with standardized criteria for diagnosing mental health conditions (aka. DSM- the Diagnostic and Statistical Manual of Mental Disorders). Unfortunately, we don't have a DSM for other species, but we know that other species (especially those observed in captivity) show signs of anxiety and repetitive behaviours. Observations like these in this study, provide valuable insight into how we could use the different bodily behaviors of animals to predict cognitive changes and help diagnose and address the mental health of captive species. These type of studies, help us deepen our understanding of the mind-body connection across species and I'm excited for what implications this might have for animal welfare as well. As caretakers of the planet (whether willing or reluctant), we owe it to the planet to understand how we might lessen suffering not only in our own species but also in other species with whom we share this panet. I believe that the insight gained through this, will help us better address our own responsibilities to the planet, deepen our connection with all of life and deal with our own uniqueness as the neurotic, paedomorphic bipedal ape which we are...

To read more about this study, check out the original paper: Affective bodily responses in monkeys predict subsequent pessimism, but not vice versa (link here). You can also learn more about the lead author, Dr. Sakumi Iki, on their faculty page.