Picturing Personhood: Brain Scans and Biomedical Identity (review)

In Picturing Personhood, the anthropologist Joseph Dumit positions himself as a relativist who questions "the constellation of codes of 'objectivity,' 'normality,' 'automaticity,' and 'veracity'" (p. 143). His inquiry takes us through a gallery of PET images of human brains. "PET," an acronym for Positron Emission Tomography, is made up of "positron emission" from physics and "tomography" from computer visualization, and the name suggests that this is an interdisciplinary field. Indeed, physics, chemistry, computations, statistics, neurology, and cognitive psychology meet in PET. And with a similarly interdisciplinary approach, Dumit sets out to study PET through a lens that is "part cultural studies and philosophy . . . part history . . . and part anthropology" (p. 13). Such a study need not be limited to PET, since it would be appropriate for other brain-imaging technologies, and especially for the other major functional imaging process, fMRI (functional Magnetic Resonance Imaging).

To introduce authentic and authoritative voices, Dumit conducts many interviews and lets experts of the participating disciplines talk for themselves. This makes room for many perspectives and insures against misplaced reverence toward "ultimate truth." Dumit emphasizes that brain imaging is built on assumptions, has technological shortcomings, is applied to brains with individual variability, and leads to data interpretation that depends greatly on the scientists who produce the image and read it. These qualifications of brain imaging shake the authority that we tend to attribute to colorful pictures as telling a "true" and "real" story.

In the first half of the book Dumit introduces some of the technological intricacies of PET. This is an uneven journey in which some of the expert explanations are lucid but others are less satisfying. Opening the black box of brain-imaging exposes both the potency and the shortcomings of PET technology. The potency is in the "visuality of these images" (p. 58). The issues involved in creating the image unfold as the reader learns about this complex process. Finally, the reading of the image is challenging and is the focus of Dumit's attention.

Usually when we see a picture we trust that we understand it, and we take its content to represent a fact in the world. Not so simple, says one judge when PET images are brought before his jury. Interlude 3 and its succeeding chapter 4 take up the use of PET in courtrooms and the notion of expert images: "The use of expert images in the courtroom is fraught with difficulties . . . stemming from our current cultural semiotics that privileges machines over experts in terms of objectivity" (p. 133). Machines, of course, are also products of human experts. The information, however, cannot be simply read from the image: the image has to be accompanied by a human expert and, unlike most other visual images to which we have grown accustomed, can easily be misread by a layperson.

Even the experts are challenged. An interview with Henry Wagner highlights the danger of confusing scientifically useful conventions with some truth: "putting anything into a category should be done not because there is some kind of intrinsic truth to it but because it is useful" (p. 181). This presents a profound challenge to the human scientific quest: how do the tools that we use in research, whether theoretical or physical instruments, affect our understanding? The final chapter, which looks at PET images themselves, comes to the conclusion that "understanding a PET image of a person with depression requires . . . reflection on categories of people and metaphors of the brain, as well as imaging technologies and practices" (p. 185).

What began as an anthropological study of the PET culture evolved into a study of the interaction between PET and the larger culture. Dumit raises many questions (maybe too many), but especially that of objectivity. PET imaging is not a simple recording of an objective truth but rather a sophisticated scientific-technological-cultural process, whose outcome is formed by...