Archive for September, 2003

030909 – Dennett’s competing drafts

Tuesday, September 9th, 2003


Well, I think I finally begin to understand Dennett’s idea of multiple competing drafts.  What he’s getting at is very much along the lines of my flow of patterns concept.

What characterizes processes in the brain?  Lateral inhibition seems to be a fundamental process that has been adopted in the course of evolution because it has the effect of sharpening boundaries.  Hebbian learning seems also to be a fundamental process that has been adopted in the course of evolution because it has the effect of collecting similar patterns of activation together.  Taking the simple Hebbian learning paradigm as a starting point, evolution has selected a number of variants for preservation and refinement: populations of neurons vary in terms of their “plasticity per unit time” and their plasticity as a function of neurochemical modulators.

On the outputs (efferents) side, it may be that lateral inhibition is what helps resolve race conditions.  There is clearly some sort of winner take all process on the efferents side, although its scope is clearly not global because we can in fact walk and chew gum at the same time.

Suppose each neuron in the brain is connected to about 10,000 other neurons, and suppose arbitrarily that on the order in half of those connections are afferent and the other half are efferent.  Then if there are about 20 billion neurons in the brain and each receives input from 5000 other neurons, there must be about 100 trillion synapses in the brain[1] and who knows how to factor in the 200 billion glial cells that cluster around certain synapses.  This calculation makes me wonder about the distribution of glial cells.  There clearly are many fewer glial cells and there are synapses.  Something I read makes me think that the glial cells are associated with axonal synapses, but even that, at least if my estimation of 5000 axonal synapses per neuron is correct, still leaves many fewer glial cells than synapses.  About the only additional assumption I might make would be that the glia are associated with axonal synapses on cell bodies.  That might make the numbers come out right, but I don’t think so.  So I guess I’m still left puzzling over the distribution of glial cells.

Nonetheless, 100 trillion synapses is a lot of synapses.  Now go back and think about the so-called Chinese room puzzle.  The hapless person in this room is busily simulating with pencil and paper the activity of 100 trillion synapses.  It will take an awfully long time to simulate even a few seconds of brain activity.  Suppose the simulation interval (granularity) is one millisecond.  To simulate a second will require evaluating 100,000 trillion synapses.  Suppose the person is very fast and can update the state of a synapse in a second.  A year is about 30 million seconds. 100,000 trillion seconds is roughly 3 billion years.

=============== Notes =================

[1] Jeff Hawkins 2004 (p.210) estimates 32 trillion, but he doesn’t say how.  Hawkins, Jeff with Blakeslee, Sandra.  2004.  On Intelligence.  New York: Times Books, Henry Holt and Company.

030907 – Rationality and communication

Sunday, September 7th, 2003

030907 – Rationality and communication

Following up on Watzlawick, et al., Pragmatics of Human Communication I find that in later discussions by the “communications” community, there is an unspoken assumption that communication has rational motivation.  For example, quoted from Dirk Schouten, “Real Communication with Audiovisual Means”


Habermas divides speech acts (what someone says) into two principal categories.  There are Strategic actions (speech acts which make people do things) and Communicative Actions (speech acts which are designed to arrive at a common understanding of a situation).


Speech acts, according to Habermas contain a propositional and a performative part (like Watzlawick and Austin, he believes that when we say something we also do something.) The propositional part indicates a state of affairs in reality. For example: “The average income of farmers in South America is just 87 dollars per annum”. The performative part implies or indicates how the propositional part needs to be understood (in this case “The speaker thinks this is disgraceful”). In that way one can categorize or question something. An audience can respond: “I think that is disgraceful, too.” Or: “Why do you think it disgraceful?” Or: “I see what you mean, but…”

In fact a speaker, by saying something, not only says something that is true to her, but also says: “I claim the communicative right towards you to have an opinion and to say it to you in this defined situation”. The performative part defines the boundaries of the communicative action. It marks out the (communicative) context of the (propositional) content. It makes clear which relation the speaker wants to make to their audience. As long as the participants are aimed at reaching mutual agreement, a communicative situation is shaped, because the speaker makes three “validity claims” with their speech act:

1. They claim that they are speaking the truth in the propositional part of the speech act;
2. They claim normative legitimacy concerning the communicative act in a smaller sense (the performative part); and
3. They claim truthfulness/authenticity concerning the intentions and emotions they express.

These validity claims the speaker makes can, in principle, be criticized, although in practice this possibility is often blocked. In communicative action the hearers can (if they wish) demand reasons from the speakers to justify their validity claims.

The problem with this analysis is that the process of originating a communication is one of shaping and selection of behaviors based on internal models and internal states.  The “intention” of behavior is to add a pattern that will move the shape of the current pattern towards a projected pattern which is created by feeding the current pattern and the “intended” behavior into the optimal projection pattern.  Huh?

Let’s try this again.  There is a current pattern of activation.  It is a combination of

existing patterns


patterns created by external receptors, enteroceptors, and proprioceptors


patterns created for and by effectors (motor patterns, behaviors)


modulating influences (generally neurochemicals)