Sunday, February 20, 2011

Decisions, decisions

kw: observations, thinking, mental health

My father has received some help with his balance and other problems from a hypnotist. He repeated a statement made by the hypnotist that we make about a thousand conscious decisions daily, while our unconscious makes a million decisions a day. That got me thinking.

Firstly, what is a decision? Upon reflection, I concluded that it is a sequence of brain activity that leads to an action or to refraining from an action. By "action", however, I don't mean just a bodily motion, but I include a mental state that differs from before, such as a realization, a word choice for a sentence one may soon speak or write, or a "mental note" to do something in the future. Do we count the sub-decisions that lead to something more major? Sure, why not?

A thousand decisions amounts to about one per waking minute. Let's consider this as a starting point. While I am writing, I can type 50-60 words per minute, but I don't always think this fast. Nonetheless, I am capable of sustained burst of "word choice" and "sentence-concept choice" in the range of one per second. When I play a computer card game such as Freecell or Spider Solitaire, I may think about a move for a minute or several minutes, and at other times make several moves per second. My hand speed limits me to about three per second. Nobody can do that all day, however.

Speaking with someone, we make one or two decisions per second, and some of us spend a lot of time conversing. Of course, half of the conversation a person spends listening, but they will be thinking, often planning what to say next, the while. So sustained decision making can approach one per second. In 16-18 hours of waking time, the number of seconds is 54,600-64,800. Thus I conclude that most of us make fewer than 50,000 conscious decisions daily, and that nobody exceeds 100,000.

What counts as an unconscious decision? When some part of the brain builds a dream image in your sleep, how many decisions are involved, and how long did it take? The visual cortex operates in parallel, and I recall dream images, just from last night, that were rather complex, containing dozens to hundreds of objects. For an image sequence to seem continuous, they must occur at about twenty per second. That is one kind of decision-making we need to consider. It parallels the recognition process that makes us aware of dozens to hundreds of items in our visual field, also at a rate of about twenty per second. In either case, a minute of visual activity is sustained by as many as several hundred thousand recognition or recall decisions. Watching an hour-long movie, which I've noticed is often visually less rich than a "real" experience, let's just guess that each minute requires 100,000 decisions (hundreds are made in parallel at every instant), so that movie prompts six million decisions by our visual processing system.

There is a lot more going on in our body; regulation of heart, liver, stomach and other organ rhythms, for example. I don't know how to analyze the number of decisions this takes, but I think it is safe to say that it does not require the sustained level found in visual processing. Then let us consider that the visual cortex is one-third of the total cortex, and the cortex is a fifth of the total brain. The cortex may then be capable of twenty million decisions per hour. The rest of the brain runs at different rates. The largest portion of the limbic system involves emotional responses, another kind of decision entirely. There may be some parallelism in this as well, but it is more mysterious overall. Then there is the memory system. Again, it is hard to decide how to count activity, and harder still to figure out what is a "decision".

Instead, let us back off and consider. The cortex alone is capable of twenty million unconscious decisions per hour, which is probably a few thousand per hour (one or two per second) in each of thousands of regions. Conscious decision making requires getting more of the brain into gear, and seems not to run in parallel.

It seems the hypnotist had his ratios about right, but the figures were wildly conservative. I suspect it is more accurate to say that we make 10,000-50,000 conscious decisions daily, while unconsciously the whole cortex makes around a third of a billion decisions…during waking hours. During sleep, the rate of activity is hardly changed, so that another hundred million or so decisions get made.

In all the above, I have considered only the cerebrum, not the cerebellum and brain stem, which regulate bodily states and mediate our decisions to perform bodily actions. I don't think I need to. The hypnotist was using the thousand-to-one figure to make the point that if we can influence how the unconscious functions operate, even a little, we can make big changes in bodily and mental states, and perhaps even rates of healing. Now that takes more consideration.

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