Friday, June 30, 2017

What Is Thought?

Is that some sort of trick question? Everyone knows what thought is. Or do they...  My questions for you today are:

  • How do you define “a thought” (yes, a single thought)? Where is the boundary from one thought to the next?
  • What is “thought” more generally? Does this cognitive activity require conscious awareness? Or language? We don't want to be linguistic chauvinists, now do we, so let's assume mice have them. But how about shrimp? Or worms?

What is “a thought”?

Can you define what a discrete “thought” is?  This question was motivated by a persistent brain myth:
You have an estimated 70,000 thoughts per day.
Where did this number come from? How do you tally up 70,000 thoughts? Do some thoughts last 10 seconds, while others are finished in one tenth of a second?

Over 24 hours, one thought per second would yield 86,400 thoughts. If “thoughts” are restricted to 16 waking hours, the number would be 57,600. But we're almost certainly thinking while we're dreaming (for about two hours every night), so that would be 64,800 seconds, with an ultimate result of one thought every 0.9257 seconds, on average.

LONI®, the Laboratory of Neuroimaging at USC, included this claim on their Brain Trivia page, so perhaps it's all their fault.1

How many thoughts does the average person have per day?

*This is still an open question (how many thoughts does the average human brain processes in 1 day). LONI faculty have done some very preliminary studies using undergraduate student volunteers and have estimated that one may expect around 60-70K thoughts per day. These results are not peer-reviewed/published. There is no generally accepted definition of what "thought" is or how it is created. In our study, we had assumed that a "thought" is a sporadic single-idea cognitive concept resulting from the act of thinking, or produced by spontaneous systems-level cognitive brain activations.

Neuroskeptic tried to find the origin of The 70,000 Thoughts Per Day Myth five years ago. He found a very bizarre post by Charlie Greer (“Helping Plumbing, HVAC, and Electrical service contractors Sell More at Higher Profits”):
Several years ago, the National Science Foundation put out some very interesting statistics. We think a thousand thoughts per hour. When we write, we think twenty-five hundred thoughts in an hour and a half. The average person thinks about twelve thousand thoughts per day. A deeper thinker, according to this report, puts forth fifty thousand thoughts daily.

If this “NSF report” exists, no one can find it (NSF is a funding agency, not a research lab). Were the LONI® researchers funded by NSF?  No one knows...

Maybe we're approaching this in the wrong way. We shouldn't be relying on descriptions of mental events to define a thought, but rather discrete brain states.

Using this definition, “a thought” is what you can capture with your fancy new imaging technique. Therefore, a thought conveniently occupies the available temporal resolution of your method:
“A thought or a cognitive function usually lasts 30 seconds or a minute. That’s the range of what we’re hoping to be able to capture,” says Kay Tye, an assistant professor in the Department of Brain and Cognitive Sciences at MIT.
In this case, the method is FLARE, “an engineered transcription factor that drives expression of fluorescent proteins, opsins, and other genetically encoded tools only in the subset of neurons that experienced activity during a user-defined time window” (Wang et al., 2017).

But what if your method records EEG microstates, “short periods (100 ms) during which the EEG scalp topography remains quasi-stable” (Van De Ville et al., 2010). In this case, thoughts are assembled from EEG microstates:
One characteristic feature of EEG microstates is the rapid transition from one scalp field topography into another, leading to the hypothesis that they constitute the “basic building blocks of cognition” or “atoms of thought” that underlie spontaneous conscious cognitive activity.

And for good measure, studies of mind wandering, spontaneous thought, and the default mode network are flourishing. To learn more, a good place to start is Brain signatures of spontaneous thoughts, a blog post by Emilie Reas.

What is “thought”?

What is called thinking? The question sounds definite. It seems unequivocal. But even a slight reflection shows it to have more than one meaning. No sooner do we ask the question than we begin to vacillate. Indeed, the ambiguity of the question foils every attempt to push toward the answer without some further preparation.

- Martin Heidegger, What Is Called Thinking?

Philosophers have filled thousands of pages addressing this question, so clearly we're way beyond the depth and scope of this post. My focus here is more narrow, “thought” in the sense used by cognitive psychologists. Is thought different from attention

Once we look at the etymology and usage of the word, no wonder we're so confused...

Does Beauty Require Thought?

Speaking of philosophy, a recent study tested Kant's views on aesthetics, specifically the claim that experiencing beauty requires thought (Brielmann & Pelli, 2017).

Participants in the study rated the pleasure they felt from seeing pictures (IKEA furniture vs. beautiful images), tasting Jolly Rancher candy, and touching a soft alpaca teddy bear. In one condition, they had to perform a working memory task (an auditory 2-back task) at the same time. They listened to strings of letters and identified when the present stimulus matched the letter presented two trials ago. This is distracting, obviously, and the participants' ratings of pleasure and beauty declined. So in this context, the authors effectively defined thought as attention or working memory (Brielmann & Pelli, 2017).2 

Alternate Titles for the paper (none of which sound as exciting as the original Beauty Requires Thought)

Aesthetic Judgments and Pleasure Ratings Require Attention

Judgments of Beauty Require Working Memory and Cognitive Control

...or the especially clunky Ratings of “felt beauty” Require Attention — but only for beautiful items.

Dual task experiments are pretty popular. Concurrent performance of the n-back working memory task also disrupts the execution of decidedly non-beautiful activities, such as walking and timed ankle movements. So I guess walking and ankle movements require thought...


1 This claim was still on their site as recently as March 2017, but it's no longer there.

2 They did, however, show that working memory load on its own (a digit span task) didn't produce the same alterations in beauty/pleasure ratings.


Brielmann, A., & Pelli, D. (2017). Beauty Requires Thought. Current Biology, 27 (10), 1506-1513.

Van de Ville D, Britz J, Michel CM. (2010). EEG microstate sequences in healthy humans at rest reveal scale-free dynamics. Proc Natl Acad Sci 107(42):18179-84.

Wang W, Wildes CP, Pattarabanjird T, Sanchez MI, Glober GF, Matthews GA, Tye KM, Ting AY. (2017). A light- and calcium-gated transcription factor for imaging andmanipulating activated neurons. Nat Biotechnol. Jun 26.

gif from palerlotus

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At July 01, 2017 5:00 PM, Blogger Smut Clyde said...

Brain and brain! What is Brain?!

At July 02, 2017 4:05 AM, Blogger Smut Clyde said...

Concurrent performance of the n-back working memory task also disrupts the execution of decidedly non-beautiful activities, such as walking and timed ankle movements. So I guess walking and ankle movements require thought...

More impact of working-memory-intensive tasks on gait: "The impact of mobile phone use on where we look and how we walk when negotiating floor based obstacles" -- Timmis et al.


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