What part of the brain keeps someone from speaking the words they think?
October 30, 2010 9:11 PM   Subscribe

What part of the brain keeps someone from speaking the words they think?
posted by airguitar to Science & Nature (9 answers total) 7 users marked this as a favorite
It's not a physical section, in the sense of something you can specifically point at (e.g. the speech center). It's a function of higher order thinking and it probably resides in the frontal lobes, along with all the other aspects of higher order thinking.

Generally speaking, the way that higher order thought works is "speculative computing". There's a mechanism which produces possible courses of action. That feed of ideas then goes through another mechanism which rejects most of it. What comes out the back end is what we do.

The reason that alcohol loosens people up is that in certain stages of inebriation, it strongly suppresses that second function, and thus the drunk person will say or do things they ordinarily would not.
posted by Chocolate Pickle at 9:29 PM on October 30, 2010 [2 favorites]

It's certainly a function of higher order thinking. There are social and demographic groups with a propensity to filtering or not filtering what they say. It's also highly individual and, to me, seems to be based on the risk/reward of the situation.

If the question is more why don't we just speak out all of our thoughts (all thoughts, not necessarily just negative ones), the recent Voices In Your Head episode of RadioLab suggests that we do entirely think out loud as children but that we learn not to over time.
posted by wackybrit at 10:04 PM on October 30, 2010

Do you mean like a one-time, tip-of-the-tongue phenomenon sort of thing, or an occasional anxiety and can't say something to someone thing, or a Broca's aphasia can't really speak at all thing?
posted by brainmouse at 11:47 PM on October 30, 2010

Not sure how severe you mean, but after my father had a stroke he developed aphasia. All the words were there but he could not at all get them out save a few which made it through his systems. Perhaps a bit of googlefu would help you track down what you're looking for if you mean this far along the spectrum?

Aphasia: http://en.wikipedia.org/wiki/Aphasia
posted by eatdonuts at 12:41 AM on October 31, 2010

In all seriousness, the same very thing that stops Deaf persons from waving their arms and hands whenever they think in words. Or the same thing that stops all of us from covering ground with our feet every time we imagine ourselves running. In other words (ha.), we sometimes forget that producing words is a physical activity, engaging several muscles and articulators in a dynamic system of precisely-timed micro events. Also, that thought in words is a sort of GUI for what's actually going on in your head.

(My apologies, as I'm making gross oversimplifications for how thought/action works. I am a linguist, but not a neuro-/cognitive linguist. Or cognitive scientist. Or neuroscientist.)
posted by iamkimiam at 4:39 AM on October 31, 2010 [1 favorite]

I have Tourette Syndrome and I do frequently blurt (or mumble or scream) thoughts that occur in my heads that I had no intention of speaking out loud. I'm no neurologist, but one of the characteristics of Tourette Syndrome is a malfunction in the inhibitory capacity of the basal ganglia.
posted by Juliet Banana at 6:02 AM on October 31, 2010 [2 favorites]

The prefrontal cortex is likely to be involved, as it makes sure you're behaving in a socially correct way and suppresses impulses.
posted by emilyd22222 at 7:07 AM on October 31, 2010

If you want to take this into completely metaphorical territory, the Freudian answer is the superego.
posted by ErikaB at 8:31 AM on October 31, 2010

One relevant anecdote is the classic story of Phineas Gage. He was a mild-mannered railroad worker for a number of years before a tamping iron, used to pack in explosive charges, set off an explosion and blew the iron through his frontal lobe. He survived, but not without dramatic changes in his personality. One consequence was that his ability to inhibit behavior was affected - he no longer could filter his words or actions.

The Phineas Gage article on Wikipedia is actually quite good. Check it out.

One of the topics I studied in grad school was the improvement in response inhibition during adolescence and young adulthood. There are several structural and functional changes in the brain that seem to be correlated with holding back an inappropriate action. A lot of the changes we saw were in the prefrontal cortex, but other cortical and subcortical areas of the brain were also involved.
posted by prefrontal at 9:03 AM on October 31, 2010

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