The Eyes Are the Windows to Our Mistakes

We all make poor decisions from time to time. Researchers at the University of Arizona are working to better understand why, and they’re looking to the eyes for answers.

To study mistake making in humans, researchers performed an auditory test on 108 participants in a lab. Each participant listened to a series of 20 clicks, some in their left ear and some in their right, over the span of a single second. They then had to decide which ear received the most clicks. Each participant repeated the task 760 times, on average, with the patterns of clicks varying in each trial.

Due to the rapid nature of the task, mistakes in responses were common, with participants giving the wrong answer about 22 percent of the time. Throughout all the trials, researchers were interested in what was going on in participants’ eyes – specifically their pupils – when an error was made.

Their findings, published today in the journal Nature Human Behaviour, add to scientific understanding of how pupil size and reactivity may correlate with mistake making, and what that may tell us about what’s happening in the brain when we make the wrong choice.

“When we make decisions in real life, we don’t have all the information presented to us at once; we have to integrate the information over time to make a decision,” said lead author Waitsang Keung, a postdoctoral research associate in the UA Department of Psychology.

“Humans don’t make perfect decisions. They’re subjected to a lot of cognitive biases, so one question is what kind of biases are they subjected to in this process of integrating evidence over time?” Keung said.

Four sources of suboptimal decision making

Using the data they collected, Keung and her collaborators examined four main sources believed to contribute to mistake making in simple perceptual decisions. They found that all four sources were at play in the mistakes made by study participants, and pupil reactivity was correlated with two of those sources.

One reason that humans make imperfect decisions is because we unequally weigh evidence we receive over time. In a perfect world, we would weigh all evidence we receive equally – in a flat line, essentially. In reality, we tend to weigh information much more unevenly.

For example, when listening to a lecture, some people might give a great deal of weight to a speaker’s opening remarks; this is known as a “primacy effect.” Others might be more heavily influenced by the concluding comments, or the things they hear last; this is known as a recency effect. Researchers refer to the pattern of how humans weigh evidence over time as the “integration kernel.”

Study participants whose integration kernel was more uneven – in other words, those who weighed the evidence they received during the task more unequally – had greater pupil dilation, or increase in pupil size. This was especially true of participants whose responses were most heavily influenced by the clicks they heard in the middle of the task than the clicks at the beginning or end.

The unequal weighing of evidence was determined to be the second leading cause of mistakes in the trials. The No. 1 source of errors, which also was correlated with pupil dilation, was so-called “noise” in the brain, or the brain’s inability to interpret input perfectly.