When we showed subjects the words “Democrat,” “Republican” and “independent,” they exhibited high levels of activity in the part of the brain called the amygdala, indicating anxiety. The two areas in the brain associated with anxiety and disgust — the amygdala and the insula — were especially active when men viewed “Republican.” But all three labels also elicited some activity in the brain area associated with reward, the ventral striatum, as well as other regions related to desire and feeling connected.
Or this one:
Voters who rated Mrs. Clinton unfavorably on their questionnaire appeared not entirely comfortable with their assessment. When viewing images of her, these voters exhibited significant activity in the anterior cingulate cortex, an emotional center of the brain that is aroused when a person feels compelled to act in two different ways but must choose one. It looked as if they were battling unacknowledged impulses to like Mrs. Clinton.
Granted, there is some hedging in these claims. But I think it's clear that the intended interpretation of the data is: Activity in the insula indicates that men are disgusted by the Republican party. And likewise, mutatis mutandis, for the other trials.
Drawing conclusions about people's mental states from brain imaging is tricky for a lot of reasons, but isn't there a very basic confusion going on here? I mean that what (say) fMRI studies give us is information about brain activity given some emotional state (or whatever), where the emotional state is identified independently by subject report or reasonable assumption. So the studies tell us that the probability of B given E is very high. But the claims above are of the reverse form: that the probability of E given B is high, enough so for us to be confident that the subjects really are anxious, disgusted, etc., based upon their patterns of brain activity. And absent background assumptions, P(B|E) and P(E|B) are completely independent, so the one tells us nothing about the other.
Is it possible that these scientists are making such a basic confusion of reasoning? Are there important and reasonable assumptions that I don't know about? Because to my eye, articles like this are really just embarrassing exercises in stamping the imprimatur of brain-scanning techniques onto the messy phenomena of human choice.
