Thursday, August 27, 2009

Hick's Law

Hick's Law relates the speed of a decision to the number of choices an individual faces. A new paper attempts to relate this reaction speed to the entropy of the distribution of the choices, and derives an estimate of 60 bits/sec throughput along the decision path.
Martín uses his method to determine how much information the brain can process during lexical decision tasks. The answer? No more than about 60 bits per second. Of course, this is not the information-processing capacity of the entire brain but one measure of the input/output capacity during a specific task.

Martín goes on to analyze the data from various types of reaction-time experiments, in particular to determine whether information-processing speed is constant during a particular task, as implied by Hick's Law. Martín reckons it isn't.

"This finding suggests an adaptive system where the processing load is dynamically adjusted to the task demands," he says. That makes sense. It seems crazy to assume that the brain carries on processing data at the same rate regardless of the complexity of the task at hand.

But this has an important implication: that the linearity of Hick's Law doesn't always apply. So Hick's Law will need some kind of modification to cope with this nonlinearity.

Just how to rewrite one of the basic laws of behavioral psychology isn't clear yet. But it's sure to involve a very different way of looking at the brain from when it was formulated.

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