Saturday, February 19, 2011

more than a feeling...,

Wired | Natural selection has nothing to worry about.

Let’s begin with energy efficiency. One of the most remarkable facts about the human brain is that it requires less energy (12 watts) than a light bulb. In other words, that loom of a trillion synapses, exchanging ions and neurotransmitters, costs less to run than a little incandescence. Or look at Deep Blue: when the machine was operating at full speed, it was a fire hazard, and required specialized heat-dissipating equipment to keep it cool. Meanwhile, Kasparov barely broke a sweat.

The same lesson applies to Watson. I couldn’t find reliable information on its off-site energy consumption, but suffice to say it required many tens of thousands of times as much energy as all the human brains on stage combined. While this might not seem like a big deal, evolution long ago realized that we live in a world of scarce resources. Evolution was right. As computers became omnipresent in our lives — I’ve got one dissipating heat in my pocket right now — we’re going to need to figure out how to make them more efficient. Fortunately, we’ve got an ideal prototype locked inside our skull.

The second thing Watson illustrates is the power of metaknowledge, or the ability to reflect on what we know. As Vaughan Bell pointed out a few months ago, this is Watson’s real innovation:

Answering this question needs pre-existing knowledge and, computationally, two main approaches. One is constraint satisfaction, which finds which answer is the ‘best fit’ to a problem which doesn’t have mathematically exact solution; and the other is a local search algorithm, which indicates when further searching is unlikely to yield a better result – in other words, when to quit computing and give an answer – because you can always crunch more data.

Our brain comes preprogrammed with metaknowledge: We don’t just know things — we know we know them, which leads to feelings of knowing. I’ve written about this before, but one of my favorite examples of such feelings is when a word is on the tip of the tongue. Perhaps it occurs when you run into an old acquaintance whose name you can’t remember, although you know that it begins with the letter J. Or perhaps you struggle to recall the title of a recent movie, even though you can describe the plot in perfect detail.

What’s interesting about this mental hiccup is that, even though the mind can’t remember the information, it’s convinced that it knows it. We have a vague feeling that, if we continue to search for the missing word, we’ll be able to find it. (This is a universal experience: The vast majority of languages, from Afrikaans to Hindi to Arabic, even rely on tongue metaphors to describe the tip-of-the-tongue moment.) But here’s the mystery: If we’ve forgotten a person’s name, then why are we so convinced that we remember it? What does it mean to know something without being able to access it?

This is where feelings of knowing prove essential. The feeling is a signal that we can find the answer, if only we keep on thinking about the question. And these feelings aren’t just relevant when we can’t remember someone’s name.


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