Psychology has undergone the type of evolutionary change described by Thomas Kuhn in his seminal work The Structure of Scientific Revolutions(1). Like other paradigm shifts, this has been a radical change. We have moved from introspection, speculation, and observation to experiment, neurophysiology, and imaging. From the classical Greek era onward, the dualism between mind and body has existed as the constant dilemma, either implicitly, as in Plato, more mechanically, as in Aristotle, or, most notably, in the philosophy of Descartes. As eloquently described by Michael Stone in Healing the Mind(2), there was a transition from earlier thinkers’ emphasis on introspection and the "body-mind problem" to biological psychiatry. This emphasis on biology and chemistry, however, neglects the human personality itself and the entire question of consciousness. Early investigators were like the physicist described by Albert Einstein in his analogy of the watch:

In the 21st century, however, we have opened the watch and have started to disassemble the mechanism. For many years, the brain was a "black box" that was subject to an input-output analysis, such as constitutes a neurological examination. A neurologist strikes the patellar reflex, causing a stretch of the tendon, which is followed by a muscular contraction. Given that observation, and many others, the location of a brain lesion may be inferred by an analysis of the response to that stimulus and some knowledge of neuroanatomy. Unfortunately, as one works up the spinal axis toward the brain, the same input may produce quite different outputs, i.e., speech or action, not only by different people but also within the same individual at different moments in time. Whether one ascribes this to the concept of "will" or to the grand results of chaos theory, the situation is extremely complicated. Psychology attempts to explain deviations from normal behavior (if that can be defined) to psychopathology by analyzing the interplay among biological processes and the external world. It seems remarkably simple and obvious to consider the problem of mental illness in a developmental way, in the way that a botanist might understand the complexity of a tree by examining the sprouting of a seed, or an embryologist the shape of the body by looking at the embryo transiting from a fetus to maturity.

What Bruce Pennington has done is to integrate the biological and psychological levels, including molecular genetics, neuroanatomy, and neuropsychology, with the help of epidemiology and experimental psychology, into one multidisciplinary work, which attempts to produce a new understanding of psychopathological disorders.

The book is organized into six sections: 1) Fundamental Issues, 2) Methods of Syndrome Analysis, 3) Disorders of Motivation, 4) Disorders of Action Regulation, 5) Disorders of Language and Cognitive Development, and 6) Conclusions.

Pennington deals with the nature-nurture problem by demonstrating that it is an interaction rather than an either/or situation. Not subscribing to one universal theory, he puts together insights from all of the various ways of looking at the brain and behavior, using the principle of mutual constraint. Pennington describes this as "conceptual integration" or "vertical integration." He points out that as physics constrains chemistry, and chemistry constrains biology, all of these are constrained by evolutionary theory. A theory that violates the laws of physics or chemistry obviously is invalid. The "black box" or "Einstein’s watch" are no longer entirely mysterious, because whatever is in them must follow the reactions described by neuroscience.

Pennington begins the book with a concise and lucid discussion of the fundamental issues, emphasizing that despite the genetic endowment, each stage in development will have sensitivities related to the timing of environmental events, or teratogens, and social risk factors. There are no grand theories here but, rather, a quite readable exposition of the tools of epidemiology, behavioral and molecular genetics, neurobiology, and neurophysiology. Each of these tools has its own rules, and all are essential to understanding psychopathology. Neuropsychology, with its emphasis on measurement and localization, also depends on development. At the analysis level of symptoms it is demonstrated that a given psychopathological change varies with a developmental stage. As physiologists of human behavior, psychologists are incorporating genetics and human interactions with the environment in a longitudinal view of the development of psychopathology.

Having briefly and succinctly described the methods of behavioral and molecular genetics, epidemiology, neurobiology, and neuropsychology, Pennington divides the areas of psychopathology to be considered into disorders of motivation, disorders of action regulation, and disorders of language and cognitive development. The disorders of motivation include depression and dysthymia, the anxiety disorders, posttraumatic stress disorder, and bipolar disorder. Beginning with the definitions, moving on to distribution in populations, epidemiology, and brain mechanisms so far as they are currently understood, Pennington discusses the major psychological theories, including those of Freud, Seligman, and Beck, and the theories of reinforcement. After reviewing these theories and demonstrating the social integration that demonstrates the incompleteness of each, he presents a section on treatment. Again, empirical data are presented regarding pharmacological and psychosocial treatments. The same scheme is followed in the disorders of action regulation, which include attention deficit hyperactivity disorder, conduct disorder, Tourette’s syndrome, obsessive-compulsive disorder, and schizophrenia. Particularly interesting are the disorders of language and cognitive development, including autism, mental retardation, dyslexia, and other language disorders. These are treated in some detail, including findings on structural neuroimaging studies and genetics. Because these disorders touch more directly on the fundamental processes of thinking, they are particularly important to the understanding of the developmental approach. Distinctions between the spatial cognition of Williams syndrome and autism, and the various forms of dyslexia and other language disorders, bring us closer to understanding the brain mechanisms of all sorts of thinking.

Pennington has a gift for lucid and logical exposition. For instance, in the Neuropsychology of Dyslexia section, the importance of listening comprehension to skill in reading is contrasted to written language, which must be explicitly taught as a cultural invention, unlike learning to speak. Experimental evidence has shown that skilled readers understand words either in isolation or in connected text, whereas poor readers have to guess the meaning of single words. Eye movement studies show that skilled readers skip "function words" such as "the," and "and." The experimental data showing the difference between normally developing readers and those with dyslexia allow for hypothesis testing using the tools of neuroscience and epidemiology. Mapping the symptoms of dyslexia to underlying processing mechanisms and incorporating data from lesion patients point the way to developing new cognitive theories and research.

Pennington does not disparage the autonomy of the multiple scientific disciplines required for integration into the new science of psychology. Rather, he demonstrates how each pulls on the other to produce the neuroscience approach. He summarizes this approach:

According to Pennington, the provisional nature of DSM-IV-TR, a descriptive book based on symptoms, may result in misleading distinctions. What is needed is a classification based on causality. Unfortunately, we lack a pathogenesis: many of the conventional mental illnesses have multifactorial interacting causes. Of course, this problem is not exclusive to psychiatry. Throughout the history of medicine thematic classifications have yielded to etiological ones as science progressed. Epidemiology and genetics have rejected the "one disorder one gene hypothesis" and replaced it with the concept of "quantitative trait loci" acting probabilistically with environmental factors to raise or lower risk.

We do not yet know which genes are necessary or sufficient, except for a very small number of conditions. Most of the psychiatric conditions are more complicated than, for instance, Huntington’s chorea or fragile X syndrome. Even finding the genes for a human condition does not reduce the importance of the developmental process. How risk factors influence genetic mechanisms is a major area of ongoing research. Likewise, the study of brain chemicals is limited by the sensitivity of the methods and the multiplicity of the neurotransmitters involved. PET and fMRI are still too crude to be used for the diagnosis of mental illnesses. We do not know which of the changes seen on these wonderful pictures are the causes, which are correlations, and which are effects. Again, a developmental approach could help to elucidate the changes seen in our imaging and neurochemical studies. The Development of Psychopathology: Nature and Nurture, therefore, describes the new paradigm of psychology, which emphasizes the complex interacting systems from genetics to the person in the environment. Psychopathology, according to Pennington, restricts the options for individuals to deal with the world around them or may be adversely affected by feedback, which then modifies gene expression.

This is an excellent textbook that provides a concise summary of the methods for genetics, epidemiology, brain mechanisms, and neuropsychology, by going through the four levels of analysis: the etiological level of genetic and environmental influences, the level of brain mechanisms dealing with neuroanatomy and neurochemistry, the level of neuropsychology, and the level of symptoms. Pennington provides a road map for future research with a framework from which to organize psychological constructs of personality and motivation. He argues against both dualism and reductive materialism when examining the mind/body problem but presents the strong argument that none of it makes very much sense without a developmental approach. This volume succeeds as an introduction to an integrative approach to the complexities of understanding the brain. With an emphasis on methodology, it provides an outline for research and psychopathology. Every clinician and researcher of psychiatry or psychology, especially those who want more than a cookbook or a work of interest only to historians of science, should read this book. This is a useful reminder that science is a method, not a compendium of "facts." As Einstein pointed out, a scientist believes that, as knowledge increases, one’s picture of reality will become simpler and simpler and would explain a wider and wider range of sensuous impressions. The scientist may also believe in the existence of the ideal limit of knowledge and that it is approached by the human mind (3).