This is a series on the book Gödel, Escher, Bach: An eternal golden braid by Douglas Hofstadter.
Earlier diaries are here
Today we will discuss Brains and Thoughts p. 337-365
From the overview
"How can thoughts be supported by the hardware of the brain?" is the topic of this chapter. An overview of the large-scale and small-scale structure of the brain is first given. Then the relation between concepts and neural activity is speculatively discussed in some detail.
This chapter stands somewhat apart from the main flow of the book. One clue to this is that neither Godel nor Escher nor Bach is mentioned. In addition, neuroscience is an area in which there has been enormous research in the decades since GEB was written - research I know little about.
So, today will be a little more free-form.
One theme in this chapter was set by the two previous Dialogues: Prelude and Ant Fugue: Is a human brain like an ant colony?
One point that is central is the sheer complexity of the human brain. On p. 340, Hofstadter notes that there are about 10,000,000,000 neurons in the brain, each of which can fire up to 1000 times per second, based on inputs from up to 200,000 other neurons and sending signals to one or many neurons.
This means that there are 2^10,000,000,000, or about 10^2,000,000,000 possible brain states, and that the state changes substantially more than 1,000 times per second (each neuron can fire up to 1000 times, but not all in synchrony. The total number of atoms in the universe is only about 10^81.
If you are interested in more detail about the brain, one place to start is with the human brain coloring book
On page 342 Hofstadter raises the question of whether specific thoughts, emotions, and so on can be linked to specific neurons or regions in the brain. The other question is, if not, then where are they? There are om many thoughts, feelings and so on! Each can't have only one neuron, as there are only some billions of neurons, and there are certainly more than that. But perhaps the key is the much, much MUCH larger figure 2^10,000,000,000?
On page 344 he gets into the question of whether there is a 'grandmother cell' that we use to recognize our grandma, pointing out that we hav to recognize her in many different contexts, and that she never looks exactly the same way twice. Any theory of this will have to also account for:
a) How we sometimes fail to recognize people
b) How we somestimes 'misrecognize' people (that is, we think a person is someone, but really the person is someone else)
c) How different people are better or worse at recognizing others
d) Why it is easier to recognize people in context
e) Why it is easier to recognize people we know well.
I speculate that a key to this is, again, that huge number. Perhaps, in some forms of learning (especially linguistic learning) we are training our 'selves' to associate certain of that huge number of patterns with certain words? So, 'grandma' is associated not only with certain visual images - a human body, certain facial characteristics and so on, but also other sensual patterns (a certain smell, sound, and so on) and certain contexts.
Perhaps, then, there is a threshold of similarity between patterns among our neurons and grandma. Part of that threshold is reached when we have a certain context - say, our parents' living room. More when we see a certain type of face - with each characteristic bringing us closer to the threshold. I think this deals with all of a) through e), above.
On page 346 Hofstadter gets into similarities among brains. I wonder how similar identical twins brains are - and how do they get more dissimilar through life?
On page 348 he talks about localization - but is this necessary? Grandma, as I noted above, is probably located in some combination of areas of the brain - visual, auditory and so on.
On page 351 he talks about 'classes' and 'instances' ... but what if these are not categories but continua? That is, a thing is not EITHER a claass OR an instance, but both a class and an instance to different degrees.
He traces this a little with his hierarchy:
- A publication
- A newspaper
- The San Francisco Chronicle
- The May 18 edition of the Chronicle
- My copy of the May 18 edition of the Chronicle
- 5) My copy of the May 18 edition of the Chronicle as it was when I first picked it up
but the hierarchy is not so simple! What of
2') A California publication
2'') A news publication
2''') A printed publication
2.5') A San Francisco publication
2.6') A San Francisco newspaper
and so on?
On page 353 Hofstadter say that
A fresh and simple instance is like a child without its own ideas or experiences - it relies entirely on its' parents experiences and opinions and only parrots them. But gradually, as it interacts more and more with the rest of the world, the child acquires its own idiosyncratic experiences ....
I think this passage could only be written by someone who does not have children! I wonder if Hofstadter would change this, now that he does, in fact, have children? (He was very young when he wrote GEB)>
Also on p. 353 he talks about how we react when we first start listening to a sports broadcast. But this will vary hugely depending on what we know about the sport in question. A real fan, one of the obsessive sorts, could hear the name of one player on a team, and immediately know a lot! Not just the position the player plays, but his/her team, opponent, record, and so on. OTOH, someone who knows very little about the sport will have only the vaguest of notions.
On p. 360 he states that 'it is apparent that no other species forms general concepts as we do, or imagines hypothetical worlds'... This is not apparent to me, and, in fact, I think it is incorrect.