It’s All in the Pupils: What your Eyes Say About Your Decision-Making Abilities

“Never trust a man with dilated pupils” as my mother used to say. Or something like that. Okay, maybe not.

But if she did, there was some truth to it. A recent article published in Plos-One by Peter Murphy at the University of Leiden has shown a correlation between pupil size and accurate decision-making.

At its core, Murphy’s study, “Pupil-Linked Arousal Determines Variability in Perceptual Decision Making” – it’ll make more sense as you read, promise – was designed to explore some of the factors that play into the cognitive process of making a decision.

And there’s plenty of reason to do so. Decision-making is one of the most common mental tasks we humans perform on a day-to-day basis. Whether you’re wondering if you should take the interstate or a side road, if you should attend a certain function, or if you should keep reading this article, you’re picking between options A and B. For all that, the neurological nuts and bolts behind this all-important process are only just beginning to be truly understood.

Not So Simple Choices

An awful lot of brainpower goes into even the simplest of choices, which equates to an awful lot of complications. Researchers have known for a long time that if you present the exact same decision-making scenario to a group of testers, you’ll wind up with an enormous amount of variability. Both timing and accuracy can vary widely from person to person; Murphy’s study sheds some light on one of the reasons why.

And it’s – drumroll please – arousal. Arousal in this case is a broad-spectrum term simply meaning: “an organism’s state of responsivity to external stimulation.” Granted, we suppose a narrower definition of arousal might also impact decision-making, but we’ll let that slide.

What your Eyes Say About Your Decision-Making AbilitiesArousal is a key factor in human attention and alertness. At an optimal, intermediate state, we’re able to easily focus on given tasks. If we’re in a low-arousal state, we tend to be sluggish and slow to engage – if we’re in a high-arousal state, we tend to be distractible. Just think of how caffeine might affect you during a rough day at work: at no cups you’re a zombie, at one you’re effective, at four you’re twitching and unable to type.

So, arousal obviously affects decision making. The problem scientists faced was measuring it. Quantifying brain activity has never been an easy task, though there are ways to do it. EEGs and MRIs both help researchers visualize an individual’s cognitive reaction to something, but they’re far from convenient.

Researchers often find less tech-heavy ways to get into their subjects’ heads. Measuring response time has long been a staple of cognitive science – reflexes aren’t easy to fake, so response time is generally seen as an honest indicator of cognition. Similarly, the team at the University of Leiden decided to use pupil dilation as an indicator of arousal levels. As you might expect, larger pupil diameters correlate to higher levels of arousal.

And the Results Say…?

The actual test put the study’s 26 participants into a relatively simple decision-making scenario. A random dot motion test, or RDM, requires testers to quickly determine what direction a cloud of dots is moving in. Not exactly the toughest dilemma, but it was more than enough for the Leiden team to draw some interesting results.

That said, they’re not really the most shocking results. As you might expect, testers in a heightened state of arousal made less accurate choices. Anyone who’s ever made a poor, stressed-out snap decision has probably suspected as much.

Not only that, but the higher testers’ arousal level was, the more variability there was in their reaction times. Predictably, higher arousal often led to an increase in extremely quick decisions, which were often wrong, but it also led to a relative increase in very slow decisions, which were… also often wrong.

This might all seem a little obvious. However, Leiden’s study was valuable on several levels. First, it did lend some credence and support to the importance of level-headed decision-making. Second, it laid an enormous amount of scientific groundwork for future studies in the same field.

Being able to measure and account for arousal states can help other researchers design studies that might otherwise be confounded by this relationship; additionally, it also sets up a great deal of future work that could help us further understand and refine the process of making decisions.

Finally, what does this mean for you? As far as everyday life goes, not all that much. Unless you’ve got some very, very keen eyes, you won’t be able to accurately measure another individual’s arousal level – how big their pupils are – on the fly. If anything, take this to heart as confirmation that, when making a major life choice, it’s best to sit back, relax, and engage without getting too excited.

That tends to be a good idea in general when talking about eyes. We’d be remiss if we didn’t mention the good that keeping calm can do for your eyes. Keeping your stress levels down, just maintaining a relaxed state, can do wonders for your eye health.

No matter how you slice it, you’re looking a long list of good reasons to remain calm.

Those of you who like to make their decisions in a state of screaming panic will likely ignore this anyway, but we thought we’d try!


About Orlin Sorensen

My vision started to get blurry as a young teenager. Soon I was wearing glasses for just about everything. This was a hard blow for me because I had always dreamed of becoming a U.S. Navy fighter pilot which required perfect vision without glasses or surgery. But I wasn't ready to give up on my dreams, so I looked into every possible alternative which led me to eye exercises. Through daily vision training and eye exercises, I improved my vision from 20/85 to 20/20 and passed the Navy's visual acuity test. In fact Men's Health declared this one of the "Greatest Comebacks of All Time!" Now, I'm sharing exactly how I did it with the program that helped me so people like you can improve your vision safely and naturally, without glasses, contacts or laser surgery.

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