Of Maggots and Brain Scans


Anne Fausto-Sterling in The Boston Review of Books:

Consider the case of Grady Nelson, a Florida man who was convicted of murdering his wife, Angelina Martinez. During the 2010 hearing to decide if Nelson should be sentenced to death, his lawyer showed the jury an image suggesting that Nelson had an abnormality in his left frontal lobe. At least two jurors were impressed by the evidence, shifting the voting balance toward life imprisonment. As much as I oppose the death penalty, the outcome raises some basic questions. Was the brain scan taken at the time of the murder, or, more likely, after years in jail? Could the brain deformations be linked to the murder? Scientifically, the introduction of this neural image was pretty lame, but the emotional impact was huge, and it carried the day for the defendant, who escaped execution.

Or what about the flurry of news stories this past December with headlines such as “Brain wiring in men, women could explain gender differences,” all reporting on a publication in the Proceedings of the National Academy of Sciences, which used neural imaging to produce average connectomes for brains of several hundred males and females.

Again, the images are compelling, but the science is not. First, neither the Proceedings article nor any other reputable research has tied specific wiring diagrams to variation in behaviors or cognitive skills. Just as with the fly larvae, the activity of differently wired networks can lead to the same behavior. Indeed, in an earlier study, the Proceedings researchers showed only small differences in the “big skills”—map reading, social cognition, spatial processing—that supposedly separate men from women. Second, the researchers do not assess the possibility that different experiences of gender might themselves produce differently wired brains. Did the young people in their samples play the same sports, have the same hobbies, wear the same type of clothing, or study the same subjects in high school?

More here.