Even Experts Don’t Know what Brain Scans Mean

For some reason, many people find neuroscience more compelling than psychology. That is, if you tell them that men seem to like video games more than women, they are unconvinced, but if you say that brain scans of men and women playing video games showing that the pleasure centers of their brains respond to video games, suddenly it all seems more compelling.

More flavors is more fun, and the world can accept variation in what types of evidence people find compelling — and we’re probably the better for it. In this case, though, there is a problem in that neuroscientific data is very hard to interpret. Jerome Kagan said it perfectly in his latest book, so I’ll leave it to him:

A more persuasive example is seen in the reactions to pictures that are symbolic of unpleasant (snakes, bloodied bodies), pleasant (children playing, couples kissing), or neutral (tables, chairs) emotional situations.The unpleasant scenes typically induce the largest eyeblink startle response to a loud sound due to recruitment of the amygdala. However, there is greater blood flow to temporal and parietal areas to the pleasant than to the unpleasant pictures, and, making matters more ambiguous, the amplitudes of the event-related waveform eight-tenths of a second after the appearance of the photographs are equivalent to the pleasant and unpleasant scenes. A scientist who wanted to know whether unpleasant or pleasant scenes were more arousing could arrive at three different conclusions depending on the evidence selected.

Daniel Engber in Slate has more excellent discussion of this problem.

Similarly, many posts ago, I noted that another Harvard psychologist, Dan Gilbert, prefers to simply ask people if they are happy rather than use a physiological measure because the only reason we think a particular physiological measure indicates happiness is because it correlates with people’s self-reports of being happy. In other words, using any physiological measure (including brain scans) as indication of a mental state is circular.

Kagan (2007) What Is Emotion, pp. 81-82.

PS Since I’ve been writing about Russian lately, I wanted to mention an English-language Russian news aggregator that I came across. This site is from the writer behind the well-known Siberian Light Russia blog.

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