American Scientist

The Face in the Mirror: The Search for the Origins of Consciousness. Julian Keenan with Gordon G. Gallup, Jr., and Dean Falk. xxvi + 278 pp. Ecco/Harper Collins, 2003. $24.95.

In The Face in the Mirror, Julian Keenan weaves together diverse findings in comparative psychology, developmental psychology and neuroscience to address an issue fraught with controversy—the origins of consciousness, which he equates with self-awareness. His background qualifies him well to discuss the topic: A former student of psychologist Gordon G. Gallup, Jr., and anthropologist Dean Falk (who are both included as contributing authors), Keenan did postdoctoral work with Alvaro Pascual-Leone at Harvard Medical School and is now director of the Cognitive Neuroimaging Laboratory at Montclair State University. He has collaborated with numerous neuroscientists and has published several scientific papers investigating the neural basis of self-awareness.

Keenan begins by recounting Gallup's discovery (reported in Science in 1970) that chimpanzees seem to recognize themselves in mirrors. Chimpanzees, after being given the chance to play with a mirror for 10 days, had a mark placed on their foreheads while they were anesthetized. Later they seemed to have no awareness of the mark until given access to a mirror, after which they began to touch their foreheads, using the mirror to guide their hands as they touched the mark on their own faces (rather than the mark on the mirror image). Gallup interpreted this behavior as indicating self-recognition by the animals. Mirror self-recognition has since been demonstrated in all great ape species, but it has not been clearly demonstrated in monkeys.

In Gallup's view, the ability to show mirror self-recognition implies awareness (or consciousness), which in turn implies the ability to monitor one's own thoughts—a long-standing definition of self-awareness—and, presumably, the ability to use that information to understand the mental state of others, a capacity termed Theory of Mind. That is, knowing how my own mind operates, I can have a theory of how your mind works, and I can use my concept of what must be going on inside your head to understand what you do and do not know.

Most developmental psychologists believe that children develop Theory of Mind at about four years of age, which is about two years after they develop mirror self-recognition. Although the human developmental literature would indicate otherwise, Gallup has consistently suggested that the ability to recognize oneself in a mirror indicates that one has Theory of Mind. However, several papers in the literature dispute this posited correspondence. Some have suggested that mirror self-recognition might be the first step in a series that culminates in Theory of Mind. In their view, the cognitive capacity or capacities that underlie mirror self-recognition are necessary but not sufficient conditions for the ability to demonstrate Theory of Mind. Others dispute the interpretation that the mirror test demonstrates anything about self-awareness. A major weakness of The Face in the Mirror is that Keenan ignores these other perspectives and just accepts the view of his contributing coauthor Gallup.

Later in the book, Keenan discusses studies that employ a variety of clinical and experimental techniques to show that the right hemisphere is the locus of self-recognition in the brain. This is rather surprising, because the left hemisphere of the brain, which supports language, has long been regarded as the "dominant" hemisphere. But Keenan argues that the right hemisphere must be considered equally important.

Is Keenan correct that consciousness has its origins on the right side of the brain? Teasing apart the roles of the separate hemispheres is difficult because they are connected, chiefly through a band of fibers known as the corpus callosum. In a few individuals, the corpus callosum has been severed surgically for medical reasons. Roger Sperry studied these "split brain" patients to ascertain the cognitive abilities associated with each hemisphere, eventually winning a Nobel Prize for his work. Keenan describes these studies, which led Sperry to conclude that both hemispheres are involved in consciousness.

Keenan argues for the right side based on the results of a number of clever neuroimaging studies, many of which he conducted himself. He provides a clear explanation of the procedures, reviews the results and then concludes that these findings show the dominance of the right hemisphere in self-awareness. To complete his argument he turns to research with individuals who have lost abilities related to self-recognition as a result of damage to the right hemisphere.

Although most of the data suggest that the right frontal lobe is heavily involved, other areas in the right hemisphere are also implicated. And, as Keenan acknowledges, research has demonstrated that the left hemisphere also plays a part in self-awareness. The question of where exactly self-awareness is located is complex, and techniques for addressing it are still being refined. It is likely that this issue will be settled in the not-too-distant future and that Keenan will contribute to its resolution.

The final chapter is a speculative discussion of the evolution of self-awareness based, in part, on a limited review of the comparative literature. Speculation is necessary here because there are so few data to go on at the moment. The chapter puts forth many interesting hypotheses, but here, as elsewhere, Keenan interprets the comparative and developmental literature to support his own ideas, ignoring other viewpoints. Nevertheless, many of these evolutionary issues will soon be sorted out, when imaging studies like those Keenan describes in humans are conducted in monkeys and apes.

This timely book offers an accessible introduction to a complex topic of much interest. Keenan's presentation of the material is interesting and easy to comprehend, and I expect that his book will attract and educate a wide range of readers.—Karyl B. Swartz, Psychology, Lehman College of The City University of New York