Saturday, March 12, 2005

Moving at the Speed of Speech

Richard asks a very interesting question: How fast is the speed of (conscious) thought? The answer to that question is not easy, as there are all sorts of types of information in consciousness. Visual information, for instance, makes its way to consciousness in a very short amount of time (on the order of tens of milliseconds), and transitions as rapidly as we can take new information in. Affective information gets there pretty quickly, too. Limits on the speed of perceptual and affective consciousness are largely due to the limits on transmission and processing speeds. Some types of information (e.g., shapes, edges, etc.) are processed very early on, and very automatically, and are thus processed rapidly. Others, such as complex scenes and perceptions that require top-down influences, are a bit slower. As a general rule, effortful processing, is slower than automatic processing.

But what Richard is really interested is in the influence of inner dialogue on the speed of more deliberate conscious thought. Much of our more conceptual (as opposed to perceptual) conscious thought is in verbal form. In fact, there is evidence that information that is difficult to verbalize (like, say, non-linear, quadratic categorization rules) is not processed consciously*. So, verbalization is important for consciousness, and if much of our conscious thought is processed verbally, then it stands to reason that the speed of verbalization may limit the speed of non-perceptual consciousness.

But, speech itself is primarily processed in perceptual and motor areas of the brain, and at least at the phonetic and syntactic levels, is processed automatically, so it moves very fast. Internal speech moves along at about 4-6 Hz, which, as far as processing goes, isn't the fastest we can go, but it's far from the slowest. The main limit on this speed is motor. As decades of research on verbal working memory (and more recently, a great deal of brain imaging research) has shown, internal verbal information is processed by most of the same regions that process spoken verbal information, including the motor areas. The only real difference between spoken and internal verbal processing is where the information from the motor system gets sent.

So, once we're above the limits of the speed of speech, what really limits the speed of conscious thought is how effortful the processing is, and the extent of our cognitive load, two things that are closely related. In other words, really complex information will slow thought down, and so will consciously processing a lot of information. When I'm thinking about simple things, or talking to myself without consciously deliberating about content, I can think at about the speed of speech, but when I'm reasoning about a complex philosophical problem, or I'm consciously thinking about a lot of things at once, everything slows to a crawl.

* Ironically, while this information is more difficult to learn, once it is learned, we process it automaticlaly, so it's actually processed faster than the simpler, consciously processed information.


Oliver said...

Having a rich vocabulary would seem to speed up thought significantly. I wonder if being multilingual helps of hinders...

Clark Goble said...

What is interesting to me Chris is what you didn't touch upon, is when mental "speech" is much, much faster than speaking. It seems to me that mental speech is limited by the time phoenems take to be uttered. Mentally we can use a sign as a short hand to those words. So one might think one is "speaking" a word when really one is just making use of this sign. Further this approach enables one to use such signs as a shorthand to subconscious processing. I'm fairly convinced, after doing some "armchair analysis" that this occurs with me.

Consider reading. With normal (i.e. non-technical) texts I can read at about 3000 words a minute. Now my perception of this reading is that it is verbal. That is, it comes across as sounds in my mind just as if I were reading aloud. However as I mentioned on Richard's blog, as far back as 5th grade I noticed that both verbal and inner reading subconsciously translated words and even fragments without me being consciously aware of it.

That typically transpired with vocabulary I was unfamiliar with but which my subconscious appeared quite adept at finding a synonym for without me even being aware of it. As I mentioned I first noticed this phenomena while a kid reading alound and having the teacher stop me and tell me that I was doing it. I honestly thought I was saying one word.

Which brings me to my final point. How does this relate to the prior issue about infallibility of mental experience. If I experience reading a word like this (or saying an inner word) and can be shown that I wasn't, doesn't that offer evidence against mental infallibility? If I think I am thinking one word but am actually thinking an other, how do we deal with that experience?

Clark Goble said...

Just to add to the above. The reason I'm convinced mental speech isn't occuring at the speed of talking is that there is no way I could ever speak 3000 words a minute. Not even if I did my best to speak fast. It simply takes a minimum amount of time to pronounce each "sound" in English. Somehow my mind is able to do this with the sounds seeming right but taking less sound. The only way I can explain this is if my perception of my experiences are incorrect. i.e. my brain is adding the illusion that I said something in my inner speech that I never actually said.

syllogist said...

Somebody hasn't been reading up on Wittgenstein's philosophy of psychology...

Clark Goble said...

I suspect that we may just not fully agree with Wittgenstein.

Chris said...

Clark, we can, and in fact do pretty much constantly do, make mistakes about mental content, so long as we treat that content as unconscious. We make mistakes about our motivations (because we don't have direct access to them) and other causes of our behavior, mistakes about the content of conceptual information that was processed unconsciuosly (in the example of non-linear quadratic rules, people almost always come up with a verbalizeable rule that doesn't fit their behavior at all), etc.

The case of you feeling like you are speaking the words when you speed read probably involves highly automatized and unconscious processes which utilize conscious vision, and therefore create an impression on the conscious mind. I'm not sure exaclty why you experience it as inner speech, but that your mind mistakes what's going on is not a surprise. Consciousness spends most if it's time interpreting things that have already passed it by.

By the way, 3000 words is damn impressive!

Chris said...

Oh, I forgot to add that even though we can be mistaken about the content of unconscious thoughts and processes, it still makes perfect sense to say that you feel like you are speaking the words, even though it doesn't make sense to say that you are in fact speaking them. With pain, the question is, are we in pain when we feel pain? I think it makes no sense to say, "I feel pain, but I am not in pain." At least, no sense without treating "pain" as a scientific name that is different from its ordinary name.

Clark Goble said...

Chris, I'd agree with you regarding the English words, but I think the philosophical controversy is aiming something more subtle that the issue of thinking I'm speaking internally gets at.

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