1. Description of the obstacle

This chapter is called "Materialism and Idealism" because I believe the conflict between these two conceptions is at the basis of physiological psychology's most vivid controversy: the relationship between mind and brain. Needless to say, mind stands for mental and behavioral phenomena whereas brain stands for the nervous system. The mind-brain controversy refers, therefore, to arguments about how psychological and behavioral phenomena relate to the activity of the nervous system. As we analyze this controversy, we will be able to detect three epistemological obstacles to the progress of physiological psychology, namely: organicism, mentalism, and psychophysical complementarism.

Classifications of systems of ideas are always arbitrary to a certain extent. Thompson and Robinson (1979) chose to classify the contenders in the mind-brain controversy into seven groups, whereas Carlson (1986) settled for only two. I prefer five groups, as follows: mentalism, materialist monism, organicism, psychophysical parallelism, and psychophysical complementarism. Mentalism refers to the conception that mental events can be fully explained by psychodynamic concepts without any reference to the nervous system. This is a dualistic viewpoint, as it implies that mind and brain are distinct and independent from each other. Materialist monism refers to the conception that mental events are nothing but neural events. This is a monist viewpoint because it implies the existence of only one dimension (the neural dimension). Organicism goes one step past materialist monism, in the sense that it claims not only that mental events are neural events but also that each part of the brain is responsible for a particular class of mental events. Psychophysical parallelism refers to the conception that mind and brain are distinct but related to each other. This form of dualism may imply that mind and brain are only different sides of the same coin or even that neural activity induces mental activity. Finally, psychophysical complementarism refers to the conception that mental and neural events complement each other as causes of behavior. It should be noticed that these five conceptions could all be described as particular ways of dealing with the much broader materialism-idealism controversy. Indeed, materialist monism and organicism are clearly materialistic, mentalism is idealistic, and the other two conceptions are paradoxically both idealist and materialist.

Which of the five conceptions provide the real solution for the mind-brain controversy? The reader who has come this far in the book will certainly be able to predict that I will not even try to answer this question. In agreement with the principles of analysis described in the Introduction, I believe that my opinion about the controversy is just as good (which means: is just as bad) as the opinion of any philosopher. To tell physiological psychology which conception to choose would be a foreign intrusion into a mature science. What I can do is try to identify the conception that is implied in the experimental work of physiological psychologists. Once this is done, the remaining conceptions can be labeled as epistemological obstacles to physiological psychology.

The general feeling one has after a first contact with the literature in physiological psychology is that psychophysical parallelism is the dominant conception. To start with, the idea that mental events are correlated with neural events has a long tradition in psychology. Four of the major psychologists in the late 19th century and early 20th century made explicit statements about the parallelism between mind and brain: the highly influential William James (James 1931 [v.1, p.4]), the father of psychoanalysis (Freud 1957 [p.207]), the discoverer of classical conditioning (Pavlov 1957 [p.563]), and the creator of the intelligence test (Binet 1928 [p.35]). Contemporary physiological psychologists share the same opinion. In the area of psychopathology, psychophysical parallelism seemed unjustified for many years because only neural correlates of illnesses involving large anatomical abnormalities could be found, but it is now possible to investigate minute abnormalities at the cellular level (Kety 1979). In lower organisms, whole neuronal circuits responsible for specific behavioral responses can be isolated and studied (Kandel 1976). Even in a more complex animal such as the rat, good correlation can be observed between rich perceptual experience and the size, microscopic structure, and neurotransmitter content of the brain (Bennett et al 1964, Greenough & Volkmar 1973, Rosenzweig et al 1960).

Yet, psychophysical parallelism is not really the standard conception of mind-brain relationship adopted in physiological psychology. More than acknowledging a correlation between mental and neural events, physiological psychology assumes that mental events do not have a life of their own, that is, that mental events can be reduced to neural events. The term reduction usually means more than what takes place in physiological psychology (Churchland 1986). As Bunge (1989) pointed out, physiological psychology performs a limited type of reduction: an ontological reduction without full epistemological reduction. Even so, if we keep the Bachelardian attitude of avoiding the invasion of another science, then any type of reduction should be criticized (assuming, of course, that reductions are really viable). In this regard, I think physiological psychology has two excuses: 1) it is a common sense mentalism (and not the scientific mentalism of cognitive psychology, for instance) that is being reduced to neurophysiology and, therefore, no science is being violated; and 2) because physiological psychology is a science, we would be intruding into a science if we wanted to criticize its reductionist approach. In any event, it should be obvious that the legitimacy of materialist monism has not been rationally demonstrated. It is an a priori assumption that probably results from the general materialist mood of our times. The reduction of mind to matter is also a basic assumption in cybernetics, as Norbert Wiener used to say that if we could build a machine whose mechanical structure was entirely consistent with human anatomy and physiology, then we would have a machine whose intellectual capabilities are identical to those of human beings (Wiener 1954).

It is not difficult to see why physiological psychology needs the reduction of mental events to neural events. It can be successfully argued that a priori materialism is just as metaphysical as a priori idealism, but, once you accept materialism, mental events are a constant nuisance. After all, if you can see, touch, and disturb nerve cells, you would like to do the same with mental events. Since you cannot do the same with mental events, you assume they do not really exist. If mental events are neural events, then there is no immaterial world to deal with. Thus, we feel terrified or ecstatic, drowsy or excited, because of specific electrochemical processes taking place in our brain (Wooldridge 1972). Likewise, so-called psychological causes of mental illness are those causes whose neural basis are not yet known (Davison 1974). In general, to understand behavior is to understand the action of the nervous system (Hebb 1949).

Because the reduction of mental events to neural events is polemical, I thought it would not be appropriate to consider psychophysical parallelism as an obstacle to physiological psychology. Since materialist monism is the official conception, we are left with three conceptions that can be considered obstacles. Let's now give examples of each one of them.

2. Examples of the obstacles

In traditional psychopathology, organicism refers to the conception that every mental illness is the result of some type of brain dysfunction (Coleman 1964). This is consistent with materialist monism. However, organicism usually goes further and generates statements that have no empirical bases and serve only to mislead scientific research. The classic example of organicism as an obstacle to physiological psychology is the pseudo-science called phrenology, which was created by Franz Gall in the early 19th century and was based on the principle that each psychological faculty (intelligence, goodness, shyness, etc) is represented on a specific area of the brain (Gall 1966). Phrenology's malefic influence lasted a whole century, so much so that in 1922 D. G. Paterson and K. E. Ludgate conducted an experiment to disprove the alleged correlation between hair color and certain personality traits (Valentine & Wickens 1949).

It must be pointed out that the concept of functional specialization of the brain is not foreign to physiological psychology. However, this specialization is much less dramatic than that claimed by phrenology and, most importantly, it is a a posteriori finding derived from actual research rather than an a priori formulation. An example of functional specialization of the brain is the sensory cortex in mammals, which is not only specific as a general area (Adrian 1941, Woolsey 1958) but also contains modality-specific columns (Mountcastle 1957, Hellon et al 1973). Even better, recent studies suggest that different regions of the extra-striate visual cortex are specialized for processing information related to specific attributes of the visual stimulus (Corbetta et al 1990). On the other hand, an example of lack of specialization is Lashley's demonstration that, at least in the rat, the process of learning and retention is dependent on the quantity of functional neural tissue rather than on the anatomical specificity (Lashley 1929). The ability of animals to learn new tasks or to discriminate sensory stimuli after large ablations of the cerebral cortex has been confirmed many times (e.g., Bromiley 1948, LeVere et al 1979, Porter & Semmes 1974).

Mentalism is an obstacle to physiological psychology because it refuses to accept not only the reduction of mental events to neural events but also the correlation between the two types of phenomena. This is specially clear when mind and soul are considered to be the same thing. If human behavior is determined by the soul, then physiological psychology (or any other empirical science) will never understand human behavior. But even more mundane forms of mentalism can become obstacles. Psychoanalysis, for instance, is a radically mentalist science. The idea that the cause of the paralysis of an arm can be the repression of libidinal impulses makes no sense at all for the physiological psychologist. For the physiological psychologist, Freud described interesting phenomena but neglected the study of the physiological machinery that produce these phenomena (Fine 1980, Schaefer 1966). Naturally, pure behaviorism is equivalent to mentalism. Although Skinner's rejection of physiology (Skinner 1938 [p.4], Skinner 1976 [p.12]) may be an essential element in the constitution of behaviorism as an independent science (Refinetti 1987), for the physiological psychologist behaviorism is in error because it treats the organism as a black box and neglects the physiological processes that produce the behavior of organisms (Crick 1979 [p.183], Piaget 1979 [p.2]).

Psychophysical complementarism is the conception according to which neural events complement mental events as causes of behavior. For instance, Sperry (1969) claimed that mental events are more than the sum of the neural events that produce them. This means that mental life cannot be explained completely by the empirical researcher, since some mental phenomena transcend the material world. Mental events complement neural events as causes of behavior. It is difficult to understand why a Nobel laureate in physiology would adopt such an unnecessary, spiritualist conception. Maybe Sperry is the exception that confirms the rule of materialist monism in physiological psychology.

Another example of psychophysical complementarism can be found in the manner how the guide for psychiatric diagnosis divides mental illnesses into two main categories: illnesses that result from brain injuries and illnesses that result from a difficulty in adapting to the demands of normal life (e.g., Ullmann & Krasner 1969). This division implies that, for the psychiatrist, neural events and mental events are both causes of mental illness. For the physiological psychologist, on the other hand, mental illness is caused by neural events (and the neural events that have not been identified yet are called mental events). This conflict of opinions between practitioners and scientists will be discussed in detail in Chapter 8.

Psychosomatic medicine is another source of obstacles. In itself, the psychosomatic approach is perfectly legitimate and compatible with physiological psychology. However, sloppy definitions of psychosomatic medicine often lead to the obstructive conception of psychophysical complementarism. According to Wittkower and Dudek (1973), the psychosomatic approach gained recognition after the Second World War when it was realized that thousands of soldiers were injured by psychological tension rather than by bullets. Now, this seems to indicate that mental events (e.g., psychological stress) can act on the body. What the psychosomatic perspective really claims is that brain physiology (which the lay person calls mind) can affect body physiology. Thus a nervous ulcer is not the consequence of the mind descending to the stomach and drilling a hole; rather, it is the consequence of a change in the pattern by which the brain sends information to the stomach. Thus, when Cannon (1928) had to explain why emotional tension is accompanied by changes in the digestive system, he did not postulate some action of the mind on the body. Rather, he argued that a diencephalic nervous structure fires at one time downward to the viscera (to produce bodily changes) and upward to the cerebral cortex (to produce emotional feelings). In short, the action of nerves in the peripheral nervous system is called somatic physiology; the action of higher centers in the central nervous system is called mental activity. Mental events are neural events.