Tuesday, May 12, 2009

Free will: An interesting new experiment

In "Electrical stimulation produces feelings of free will" (Scienceblogs, May 7, 2009) Ed Yong notes, about a recent experiment involving brain cancer patients who were having tumours removed,
These contrasting responses tell us two important things. Firstly, they tell us that our feelings of free will originate (at least partially) in the parietal cortex. It's the activity of these neurons that creates a sense that we initiate actions of our own accord. Secondly, they show that the sense of moving doesn't depend very much on actually doing so - it depends on calculations that are made in the parietal cortex, long before the action itself begins.

[ ... ]

Desmurget, on the other hand, could only ever produce the illusion of movement by focusing on the parietal cortex. And his patients' descriptions of their experiences made it very clear that they were feeling some sort of internal intention to move, rather than feeling compelled by an external force. Without any prompting from the researchers, they all described their feelings with words such as "will", "desire" or "wanting to". One of the patients said, "I felt a desire to lick my lips", after a low burst of current. With more stimulation, he said "I moved my mouth. I talked. What did I say?"
I suspect that the sense arises "partially" in a number of places, including the parietal cortex.

Reading this interesting article reminded me of something: Women in the last stage of labour typically feel a strong desire to start pushing, to expel the child. But modern obstetrical staff urge them to wait until they get to the delivery room. So the mother is confronted with a dilemma - should she follow the urge of nature or the advice of obstetrical nurses? Most women in my part of the world follow the advice, not the urge. A triumph of nurture over nature, if you like, one that suggests that free will can be active even in a critical situation.

Hat tip: Stephanie West Allen at Brains on Purpose


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