Stress, arousal, and cognitive performance
From school exams to job interviews to business presentations: most people will have experienced the churning stomach and dry mouth that results from activation of the ‘fight or flight’ response. Driven by the sympathetic nervous system, this is a chemical cascade led by adrenaline and other hormones that is designed to release energy and prepare the body for strong physical exertion — such as running away from a tiger.
Whilst evolutionarily very helpful, when I’m on stage about to give a talk, it’s not exactly what I need. What I do need is an increased ability to think clearly, remember what I had intended to say, and deal calmly with any last minute technical hitches or difficult questions from the audience. So what effect do all these complex changes in my neural chemistry have on the performance metric that matters most in this situation: my cognitive function?
My subjective experience is that it can go two ways. Sometimes, the stress gives me an extra clarity of thought and I perform in a way that I rarely do during a quiet day in the office. But occasionally the pressure gets to me, my mind races and I stumble over material that I know well.
It turns out I have just rediscovered one of the earliest theories of arousal, the Yerkes-Dodson law. This states that moderate levels of arousal lead to optimal performance, while too little or too much pressure both impair it. Originally derived from experiments that studied the effects of electric shocks of varying intensities on learning in mice, it’s quite common to see the ‘inverted-U’ shape relationship between arousal and performance written as the gospel truth in psychology textbooks.
In the last hundred years, the Yerkes-Dodson law has since been criticised and improved on in a number of ways, but it remains popular — probably in part because it seems to fit our subjective experience so well.
When you think about it, it’s not completely clear that my physiological response to a business-critical situation should have much in common with a mouse’s response to electric shocks. And to understand both my physiological responses and the effect this has on performance, we’d need to study it in environments that more closely mimic my working life. One attempt to do just this measured levels of the stress hormone cortisol in 91 people who were randomised to prepare and deliver a speech in either a high- or low-stress situation. The high-stress participants were told to defend themselves against a (fictional) shoplifting charge, while those in the low-stress condition made a short video summarising a travel article they had just read.
As expected, those defending themselves against shoplifting showed higher cortisol levels and higher heart rates while speaking. However the two groups used the same number of words, and those in the low stress group actually used ‘non-fluencies’ like “umm” and “err” more frequently. People in the higher stress situation did tend to pause more during the speech, suggesting that the stress was reducing the cognitive resources available to the participants.
Now that wearable consumer devices like the Apple Watch and Microsoft Band contain a plethora of relevant sensors, we can start to study the relationships between arousal and performance in an even more realistic environment: real life. One Cognition Kit project we are running involves monitoring physiological traits such as galvanic skin response throughout the working day, and using changes in these markers to trigger a brief cognitive test. By triangulating people’s subjective experience, physiological arousal and cognitive performance we can understand how these relationships vary both between and within individuals. So next time I give a big talk and feel butterflies in my stomach, at least I know it will be contributing data to improving our algorithms!
