Thursday, April 17, 2008

Time to make your mind up

Some well-known experimental work by Benjamin Libet years ago found that action-related ‘readiness potentials’ in the brain could be detected before individuals had any awareness that they had decided to perform the (simple) action in question. The gap was a couple of hundred milliseconds.

This finding has been far surpassed in a new study, by Chun Siong Soon, Marcel Brass, Hans-Jochen Heinze and John-Dylan Haynes:

In the study, published in Nature Neuroscience, participants could freely decide if they wanted to press a button with their left or right hand. They were free to make this decision whenever they wanted, but had to remember at which time they felt they had made up their mind. The aim of the experiment was to find out what happens in the brain in the period just before the person felt the decision was made. The researchers found that it was possible to predict from brain signals which option participants would take up to seven seconds before they consciously made their decision.

Indeed, the paper states that due to the “sluggishness” of the measurement procedure, the left-or-right neural activity was actually present up to ten seconds before consciousness of the decision.

Whenever a finding like this comes out, you hear people pontificating about ‘free will’. But there aren’t really many philosophical conclusions to be drawn uniquely from this work. What it tells us is about how decision-making works and how much of that is conscious. For my money, that’s quite enough.

But the finding is perhaps not revolutionary. Consider this passage from that classic of modern literature, Thomas Harris’s Hannibal. The character in question (not Dr Lecter) has been faced with a duty-or-money dilemma:

…he believed that he was deliberating. He was not. He had already decided piecemeal.
We assign a moment to decision, to dignify the process as a timely result of rational and conscious thought. But decisions are made of kneaded feelings; they are more often a lump than a sum.

The book itself is mixed, even by the standards of a mass-market thriller. But this bit’s both perceptive and nicely phrased.

1 comment:

Matt M said...

Science Daily looks like a great resource - hadn't heard of it until now.