At a talk I attended recently, the speaker posited that the average person thinks tens of thousands of thoughts per day of which 95% are the same as the day before. My experience aligns somewhat with incessant repetition, but I took issue with a mind that conjured up a new thought every couple of seconds. Moreover, I wondered: How in the world would someone measure the frequency and content of thoughts scientifically? Time for a little research…
Early attempts at thought measurement relied upon self-reporting. Presumably, subjects kept a tally every time they found themselves thinking a thought and marked whether it was a novel one. Of course, the very act of interrupting a thought for reporting purposes would disrupt the brain’s natural processes. And I suspect that such reports were not entirely reliable.
With the advent of functional magnetic resonance imaging (fMRI) technology, scientists gained the ability to detect patterns in brain network activation and tie them to discrete objects (e.g., faces, houses). Not surprisingly, it takes a lot of work and a chunk of change to map the thought pattern for each object. Given the mind-boggling number of objects in the world, the current database proves woefully incomplete to track what people think. Moreover, the complexity of mapping thought patterns ratchets up considerably given that each thought also reflects the subject’s relationship to the object – e.g., perceiving, believing, fearing, imagining, remembering. So, I don’t place much weight in aforementioned speaker’s characterization of our daily thought patterns.
I managed to stumble upon a report by Dr. Jordan Poppenk and his research assistant Julie Tseng from the Centre for Neuroscience Studies in Queen’s University, Kingston, ON opted that gave me something solid on which to stand. They eschewed concerns about what people think in favor of determining the frequency with which subjects transition from one thought to the next (a.k.a. their mentation rate). It turns out that this inquiry can be measured reliably using fMRI data. They published their methodology and findings in the July 2020 issue of Nature Communications.1 Though I found the text rather dense scientifically, I’ll try to explain in simple terms what I think it says.
Poppenk and Tseng’s scientific progenitors took fMRI scans on subjects as they watched well-crafted movies. Participants displayed similar brain activity patterns in widespread low- and higher-order areas. These studies showed how movies exert control over our cognitive states and identified the associated neural circuitry. Poppenk and Tseng suggested that a similar mechanism existed for spontaneous thought. They reasoned that both activities involve a shift in focal point during which new information integrates with existing representations to move a storyline forward.
They analyzed fMRI data from 184 participants taken while watching a movie and at rest. They used the latter to distinguish random fragments of neural activity from contiguous, worm-like segments that arose in response to an attractor (or focal point) that stabilized neural network configurations. Having developed the means to map and measure thought worms2 for minds at rest, they applied their methodology to the fMRI data associated with movie watching. They verified that their worm-like constructs held psychological relevance. They also validated the hypothesis that a mind at rest displays the same thought architecture as a mind in a stimulus-controlled environment. As they stated in scientific jargon:
“Based on the centrality of semantics to thought, we argue these transitions serve as general, implicit neurobiological markers of new thoughts, and that their frequency, which is stable across contexts, approximates participants’ mentation rate.”
Poppenk and Tseng measured the average median thought transition rate across movie-viewing and at rest to be 6.5 transitions per minute. Assuming an 8-hour sleep cycle, that corelates to over six thousand thoughts per day. They also detected higher mentation rates for persons associated with neuroses. That finding is consistent with such individual’s susceptibility to distraction and excessive self-generated thoughts.
While advancing knowledge of the erstwhile mysterious brain, Poppenk and Tseng advocate for additional research to explore and build on their findings. Beyond satisfying intellectual curiosity, their research could lead to early detection of neurosis, schizophrenia, ADHD, etc. and open up the possibility of accelerated life-enhancing intervention.
1 See article entitled “Brain meta-state transitions demarcate thoughts across task contexts exposing the mental noise of trait neuroticism” at https://www.nature.com/articles/s41467-020-17255-9.
2 Thought worms are adjacent points in a simplified representation of activity patterns in the brain. They reflect consecutive moments when a person focuses on an idea.