Wednesday, February 14, 2007

Intention and the brain.

I'm sure most people have read this story (or some version of it) about how fMRI scans have "detected intentions" in people's brains. I sincerely hope that this conclusion isn't what's published in the actual study, as it doesn't at all follow from the data. I'll prove this by constructing some alternate claims which are equally well-supported by the same data.

(1) Intention type-identity: One pattern of brain activity (call it "stateA") is the intention to add the two numbers, one pattern of brain activity ("stateS) is the intention to subtract the two numbers.

(2) Intention type-identity with contrast: StateA is the intention to add the two numbers rather than subtract them, stateS is the intention to subtract the two numbers rather than add them.

(3) Intention type-identity of contradictories A: StateA is the intention to add the two numbers, stateS is the intention to not add them.

(4) Intention type-identity of contradictories B: StateA is the intention to not subtract the two numbers, stateS is the intention to subtract them.

(5) Purpose type-identity: StateA is the purpose to add the two numbers, stateB is the purpose to subtract them.

(6) through (8): as per (2) through (4), with "purpose" instead of "intention".

(9) through (12): as per (1) through (4), with "plan" instead of "intention".

And so on, and so forth. And, let's not neglect the possibility that there are different ways of constructing the types that are being identified. And the possibility that functionalists are right and the possible identities seen on the brain scans may be explained due to some unobserved similarity between the structures of the brains of those examined. And the possibility that there's really some unobserved intermediary acting between the intention (or other mental state) and the state of the brain. Etc. Etc. Etc.

In short, what we have here is a classic case of (radical) underdetermination of theory by data. What gets the conclusion out -- (1), the type-identity of intentions with patterns of brain activity -- is the data plus a set of contentious philosophical claims in the realms of philosophical psychology and philosophy of mind. It's the contentious claims that are really at stake. The data, although interesting in their own right, won't settle a damn thing. Anyone who thinks different is fooling themselves.

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