I will be frank: Uncertainty makes me nervous. I do not like it, and I get a little weird when there's too much of it about. It turns out, though, that there might be a scientific reason for why I have trouble coping with uncertainty — and if you, too, find that you really, really don’t like not knowing what’s coming down the proverbial pipe, it might come down to a very specific area of the brain. New research published by the American Psychological Association has discovered a connection between an intolerance of uncertainty and an increased volume of gray matter in a part of the brain called the striatum.
For the study, which was published in the journal Emotions, 61 undergraduate students at Dartmouth University first filled out two surveys: The Intolerance of Uncertainty Scale, which measured how well participants were or weren’t able to cope with uncertainty, and the State Trait Anxiety Inventory Form Y-2, which measured self-reported levels of trait anxiety. (The State Trait Anxiety Inventory Form Y-2 was used to separate out the specific effects of intolerance of uncertainty from general anxiety.) Then, they had their brains scanned by an MRI.
When the researchers compared the MRIs with the students’ survey results, they discovered that how well the students tolerated uncertainty had a significant association with the volume of the striatum. Said lead author Justin Kim, PhD, in a press release, “People who had difficulty tolerating an uncertain future had a relatively enlarged striatum. What surprised us was that it was only the striatum and not other parts of the brain we examined.”
The striatum is part of the basal ganglia — a collection of structures in the brain that are most well-known for controlling our voluntary movement. That’s not the only thing these structures do, though; they’re also thought to play a role in learning and cognition. Furthermore, the striatum mediates reward cognition and motivation: A 2007 study published in the Journal of Neuroscience found evidence that the dorsal striatum — one of the striatum’s two components (the other being the ventral striatum) — is directly involved in decision-making, particularly when those decisions relate to “encoding specific action-outcome associations in goal-directed action and the selection of actions on the basis of their currently expected reward value.” That is to say, the dorsal striatum helps us figure out what actions to take based on what we might get out of them.
Previous research has also shown that an increased amount of gray matter in the striatum correlates with obsessive compulsive disorder and generalized anxiety disorder; indeed, according to the cortico-striatal model of OCD (a model which is widely accepted), the disorder’s pathology may be attributed to the striatum. However, the current research is the first time a larger striatum has been found to be associated with an in ability to cope with uncertainty without an existing diagnosis of OCD or generalized anxiety disorder already being present.
Said Kim, “Our findings demonstrate that the relationship between increased striatal volumes and intolerance of uncertainty can be observed in healthy individuals.” However, he also noted that although having a large striatum might be associated with how well you cope with uncertainty, it doesn’t necessarily mean that you have OCD or generalized anxiety disorder. (As always, don’t try to diagnose yourself; if you think you might need to, go ahead and talk to a mental health professional. They're there to help.)
Obviously, this particular study isn’t the be-all, end-all explanation of why some of us have a harder time dealing with uncertainty than others; the sample size was pretty tiny, for one, and moreover, there are tons of other threads further research might follow to paint a bigger and more accurate picture. For example, research published in 2016 found that humans are generally hard-wired to dislike uncertainty — so much so that our stress levels peak when we have absolutely no idea what to expect from the future. It’s a leftover survival instinct, something that helped keep us safe in less advanced times. How might that factor into the current study’s results? Or consider the Need for Closure Scale — the psychological test that measures how well you deal with ambiguity. I’d be interested to know whether there’s any correlation between how people score on this scale and striatum size — or, for that matter, how they score on the Intolerance of Uncertainty Scale.
There’s plenty we still don’t know — but even if there’s a lot of uncertainty surrounding us now, there may not be in the future. And, hey, isn’t that what this is all about?