then, to raise the pressure, the test got harder and the reward got higher. an initial image would be displayed, then the screen would go blue and be blank for a full five seconds. if they got this one right, they’d be rewarded with three pellets. (“although it might seem a small difference in reward quantity, we have evidence that this population of capuchins is sensitive to the number of reward pellets received and changes their behaviour accordingly,” the study noted.)
more stress means worse performance
researchers used non-invasive fecal tests to determine the monkeys’ levels of cortisol, a primary stress hormone. they found that higher cortisol levels were associated with a lower ability to successfully complete the high-pressure trials — essentially, the monkeys who were most stressed were least likely to perform well under pressure. this part of the research “provid[ed] evidence that an individual’s long-term stress state might be related to cognitive performance,” the study found. “ongoing exposure to stress is related to the ability of an individual to cope with an acutely stressful situation and, therefore, the individual differences we see in ‘choking.'”
but there wasn’t one unified reaction to higher stress levels: a lot depended on an individual monkey’s reactions. “our results suggest that, like humans, there is individual variation in how capuchins perform on a cognitive task during high-pressure situations, with some monkeys tending to ‘choke’ and others to thrive,” the study found.
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