1. Overture

Learning a new science involves learning not only the formal contents of that science but also the particular worldview shared by the people who practice that science. The formal contents of physiological psychology have been systematized in various textbooks, some of which are listed in Table 1. On the other hand, academic education in physiological psychology has almost always neglected the description of the worldview shared by physiological psychologists. This is an unfortunate situation, as the scientific Weltanschauung, or esprit scientifique, is an essential part of the education of any scientist.

The description of the worldview of a particular science has traditionally been the job of philosophers of science. This book describes the worldview of physiological psychology and, therefore, is entitled Philosophy of physiological psychology. As it will be evident shortly, my intent is to be descriptive rather than prescriptive. Therefore, my handling of physiological psychology does not resemble Hoyle's (1984) handling of neuroethology, which understandably generated discontentment in the scientific community (Bassler 1984, Davis 1984, Simmons 1984).

Before we move into specific issues in the philosophy of physiological psychology, we must spend some time on the task of defining both physiological psychology and philosophy of science.

2. Physiological psychology

Physiological psychology is the science that studies the biological bases of behavior. For this reason, physiological psychology is sometimes referred to as biological psychology, biopsychology, or psychobiology. This means that the physiological psychologist studies the biological factors (as opposed to economic, social, or cultural factors) that cause or constitute behavior. Although the expression biological bases of behavior refers to a large number of physiological processes, contemporary usage equates biological bases with neural substrates (Davis et al 1988). Consequently, physiological psychology today is a synonym of behavioral neuroscience rather than a synonym of psychobiology as it used to be in the 1950's. I will not express my opinion about whether this neuroscience bias is good or bad, nor will I try to estimate how long the trend will last. Since the president of the United States designated the 1990's as the "decade of the brain" (Judd 1989), the neuroscience bias was probably beneficial to the extent that it improved federal funding for research in physiological psychology.

A contemporary definition of physiological psychology would refer, therefore, not to the biological bases of behavior but to the neural substrates of behavior (including the special class of behavior called mental activity). The name physiological psychology has been adopted by numerous authors (e.g., Brown 1976, Deutsch & Deutsch 1973, Isaacson 1971, Morgan & Stellar 1950, Rosenzweig & Leiman 1982, Thompson 1967, Wayner 1971), although several alternative names have been proposed, such as biopsychology (Valenstein 1973), psychobiology (Myers 1971), neuropsychology (Pribram 1954), neurobehavioral science (Isaacson 1973), behavioral neuroscience (Thompson 1983), and others. In certain instances, names that might seem alternative names actually designate subspecialties of physiological psychology, such as neuropsychology (Maher & Maher 1979, Meier 1974), psychophysiology (Ax 1964, Sternbach 1967), and neuroethology (Camhi 1984, Ewert 1980).

A number of examples and counter-examples of typical experimental studies will help delineate the boundaries of physiological psychology. Two of the most vivid examples of the study of the neural basis of behavior are the evocation of visual and auditory experiences by electrical stimulation of specific sites on the cerebral cortex in humans (Penfield 1966) and the evocation of what seems to be the ultimate sensation of pleasure by stimulation of diencephalic structures in rats (Routtenberg 1978). On the other hand, the study of the areas of the brain involved in muscular movements evoked by electrical stimulation of the motor cortex (Collins et al 1986) would belong to neurology or neurophysiology rather than physiological psychology, since only the neural component (and not the behavioral one) is being investigated. Analogously, the evocation of thermoregulatory behavior by thermal stimulation of the hypothalamus (Refinetti & Carlisle 1986, Satinoff 1964) belongs to physiological psychology, whereas the study of electrophysiological characteristics of thermal receptors in the brain (Barker & Carpenter 1970, Kelso et al 1982) does not. Naturally, this distinction implies no attribution of scientific merit or of conceptual incommensurability. Electrophysiology is as scientifically important as physiological psychology, and an electrophysiological experiment that investigates, for instance, the firing characteristics of thermal receptors in the monkey's hand (Darian-Smith et al 1979) is extremely valuable for physiological psychology if the results are correlated with results from psychophysical experiments on thermal discrimination in humans (Johnson et al 1979). The same may be said about the study of the relationship between the electrical activity of single neurons in the inferior colliculus of the newborn mouse (Shnerson & Willott 1979) and the ability of these animals to respond to acoustic stimuli (Shnerson & Willott 1980).

Many additional examples may be given. The mapping of brain regions that are active during ingestive behavior (Hall 1989) and the inhibition of ingestive behavior by infusion of nutrients directly into the rat brain (Davis et al 1981) are examples of research in physiological psychology. On the other hand, the study of the effects of changes in taste and nutrient content of food on ingestive behavior in humans (Rolls et al 1988) and the study of how taste aversion is learned in rats (Garcia & Koelling 1966) belong to behavioral psychology or regulatory physiology rather than to physiological psychology, since only the behavioral component (and not the neural one) is being investigated. Analogously, the investigation of the effects of cerebellar lesions on emotional behavior in rats (Supple et al 1987), or of cortical lesions on sensory discrimination (Finger et al 1970), or of hippocampal lesions on memory (Jagielo et al 1990), or of cortical lesions on learning capability (Brennan 1979, Gabriel et al 1979), or of hypothalamic lesions on thermoregulatory behavior (Refinetti & Carlisle 1987) are all examples of research in physiological psychology. On the other hand, the study of the sensory determinants of suckling behavior in weanling rats (Bruno et al 1980), or of social relations among non-human primates (Harcourt 1979, Sade 1967), or of the punishment procedure in operant conditioning (Azrin & Holz 1966), or of the behavioral thermal preference of the rat (Refinetti & Horvath 1989) belong to behavioral psychology and ethology rather than to physiological psychology. As before, this distinction implies no attribution of scientific merit or of conceptual incommensurability. Purely behavioral studies are just as important as studies that examine the neural correlates of behavior. In fact, physiological psychology, behavioral psychology, neurophysiology, and regulatory physiology are all interrelated sciences. Except for the few exceptions described later on in this book, all of these sciences contribute to the advancement of our knowledge of how the animal body (including the brain) performs the various tasks required for the survival of the individual and the species and for the enjoyment of human existence.

3. Philosophy of science

Philosophy of science is the study of how science goes about its own business, that is, how science obtains knowledge. If there is one thing everyone agrees on, it is that knowledge is not given a priori. In other words, knowledge must be obtained gradually. How knowledge is obtained, and even what knowledge really is, remains controversial. This controversial situation should not be too disturbing, however. After all, if we do not expect science to be a finished enterprise (where everything to be known is already known), we should not expect philosophy of science to be a finished enterprise either. One aspect of scientific activity that all philosophers of science seem to agree on is the dialectical nature of scientific knowledge. In other words, it seems clear that scientists are in a constant swing between adherence to rules of proper scientific conduct (i.e., methodologies, theories, hypothesis, etc.) and the rejection of these same rules to adopt new ideas.

In the 19th century, Wilhelm Hegel was probably the first philosopher to formally express the idea of a dialectical progression of knowledge. In Hegel's conception, not only science but all human experience progresses by solving conflicts between a previously established thesis and a new thesis (the antithesis) in such a way that a third thesis results which is closer to the absolute truth than either of the two previous formulations (Hegel 1931, 1964). The dialectical process is especially clear when traditional dichotomies are involved (such as nature-nurture, conformism-revolution, etc), but it can also be seen in more common situations such as the synthesis of communism and liberalism into the democracies of the late 20th century. It should be mentioned in passing that the dualistic logic of our civilization (which makes the dialectical process possible) has been criticized as an unworthy result of the Judaico-Christian heritage of moral impotency (Nietzsche 1918) or of the patriarchal nature of our societies (Bleier 1984). Whether these criticisms are correct or not, the fact remains that science as we know it progresses according to a dialectical process. Hegel's conception of a perfect totalization of knowledge at each step of the process may be flawed (Refinetti 1989), but the idea of progress as a continuous process of refutation and elaboration of previous assumptions is almost intuitive.

In the 20th century, Thomas Kuhn saw the dialectical process as a dynamic balance between normal science and periods of scientific revolution. During normal science, scientists are carefully trained according to prevailing rules of scientific conduct and perform their work in accordance with these rules, whereas the rejection of part or all of the previous rules characterizes a scientific revolution (Kuhn 1962). In an attempt to emphasize the importance of innovative spurts in the scientific endeavor, Paul Feyerabend suggested that a central component of progressive research is the acceptance (at the heuristic level) of every conceivable idea, even though (actually, preferably if) they have no scientific basis (Feyerabend 1975). Gaston Bachelard proposed that science could be characterized as a progressive enterprise that is constantly retarded by a number of epistemological obstacles (Bachelard 1938). Bachelard's perspective is very interesting because it avoids the centuries-old problem of deciding what is right and what is wrong in our knowledge of the world. It avoids the problem by giving up philosophical arrogance. Let's examine this matter in more detail.

The activity of gaining knowledge, which we call science today, used to be called philosophy millennia ago. As more and more disciplines branched out of philosophy, philosophy overtly maintained its gnosiologic goals well into the 19th century (Husserl 1965). That is, both science and philosophy claimed to obtain knowledge, although the objects of study were different in most cases. Naturally, philosophy of science was assumed to produce knowledge about scientific knowledge. For many years, however, philosophers seemed unable to treat science as a serious object of study. Although highly sophisticated analyses of scientific investigation were produced (e.g., Nagel 1961, Popper 1959), philosophers maintained an unjustified paternalistic attitude all along. For centuries, the philosopher believed to be able to see deeper than the scientist and, therefore, to tell the scientist how to behave. In the 16th century, Descartes prescribed general rules of thought that the scientist should follow in order to obtain knowledge (Descartes 1947). In the 20th century, Carnap believed he could extract fundamental principles from the physical sciences and prescribe them to every other branch of science (Carnap 1966). The most recent attempt to prescribe scientific conduct is probably Laudan's normative naturalism. He tries to convince us first that philosophy is a science and, then, to make us believe that empirical science is only descriptive but philosophy can be both descriptive and normative and can dictate rules to empirical science (Laudan 1990). Many other philosophers of science with prescriptive intentions are described by Losee in his interesting book about the relationship between history of science and philosophy of science (Losee 1987).

This type of philosophical arrogance found in Descartes, Carnap, Laudan, and many others is not found in Bachelard. His idea is that if we are going to study how science obtains knowledge, then we should let science speak for itself instead of telling science how to behave. As Gerard Lebrun wisely noted, the first condition for performing good epistemology (i.e., the study of knowledge) is the unconditional respect for science (Lebrun 1977). It does not matter whether science holds the ultimate, absolute truth about the world; it does hold the best truth we have at the moment. This faith in science as the possessor of the truth may seem old-fashioned, but it is actually very much in tune with the current relativist mood. In the late 19th century, Auguste Comte generated a long-lasting optimism about the power of science with his positivist philosophy (Comte 1877), and in the first half of the 20th century logical empiricism brought the positivist ideal to its highest level of sofistication (Ayer 1959). Since then, concern has been expressed about the legitimacy of some assumptions of the positivist philosophy that are now part of science, especially that of the logical supremacy of empiricism and the idea of objectivity that goes with it (e.g., Longino 1990, Polanyi 1962, Unger 1984). This "relativization" of science is intellectually exciting but should not obscure the fact that the study of science must be objective. That is, although the cultural philosopher is expected to evaluate the cultural significance and legitimacy of science, the philosopher of science should not care whether an empiricist attitude is good or bad, legitimate or arbitrary. Our faith in science is an acknowledgement of the existence of an institution called science, independently of what cultural factors contribute to the establishment and maitenance of this institution. Science today is empiricist (to a limited but definite extent), and this is what matters. More than that, as science is a potent source of knowledge in our days, what hurts science hurts knowledge. This means that an obstacle to science is a true epistemological obstacle. It also means that a normative philosophy of science is just one of many obstacles to science.

A total of 14 epistemological obstacles to the progress of physiological psychology are described in this book, namely: inflexible realism, spiritualism, naive humanism, epistemological holism, antivivisectionism, sociologism, anti-empiricism, organicism, mentalism, psychophysical complementarism, bidimensionalism, innatism, environmentalism, and clinical pragmatism. Some of these obstacles are specific to physiological psychology, whereas others affect the whole of psychology, and some threaten science in general.

In addition to the deleterious effects of epistemological obstacles, physiological psychology may have its progress obstructed also by factors of a different nature. In a broad sense, anything that reduces the time invested in research on physiological psychology constitutes an obstacle. Thus, a physiological psychologist interested in biological rhythms would be productive by studying the changes in brain metabolism that accompany circadian changes in locomotor activity (Room & Tielemans 1989) but would be obstructive by studying the cellular neurophysiology of isolated central pattern generators (e.g., Lydic 1989) because physiological psychology time would be "wasted" on pure neurophysiology. Naturally, this type of obstacle has little relevance. The scientist who leaves the laboratory earlier to avoid rush-hour traffic on the way home would generate an equivalent obstacle. Time is certainly an important commodity in our days, but it would be frivolous to point out that goofing off is an obstacle to the advancement of science. Therefore, we may consider for practical purposes that only epistemological obstacles are intellectually meaningful obstacles. A physiological psychologist who occasionally conducts pure neurophysiological research is a person with multiple interests and not an obstructor of the progress of physiological psychology.

4. This book

It should be clear by now that this book's arguments are based on two main principles, as follows: 1) the education of a physiological psychologist should include not only the methodological and conceptual body of knowledge of physiological psychology but also the worldview shared by the physiological psychology community of scientists; and 2) because philosophy of science cannot legitimize its aspiration to be normative, it can only be helpful to science (and, consequently, to society in general) if it fosters the analysis of epistemological obstacles that jeopardize the progress of scientific research. Consequently, the study of the epistemological obstacles to the advancement of physiological psychology may be seen as a contribution to both science education and philosophy of science.

As a contribution to science education, this book should be useful to undergraduates and graduate students as well as to professional scientists and educators. Although rote memorization of the epistemological obstacles described in this book would serve no purpose, awareness of their existence should prove to be extremely helpful for those who enter the field of physiological psychology. Such awareness should have two main consequences: it should produce a higher likelihood that physiological psychology will continue to develop freely, and it should stimulate reflection about one's own personal convictions regarding science and scientific knowledge. After all, to acquire the worldview of physiological psychology is to learn how to avoid the epistemological obstacles that threaten its development. Regarding general scientific conduct, one may want to read also Merton's short essay on the normative structure of science, where he suggests that four sets of moral/technical imperatives (viz., universalism, communism, disinterestedness, and organized skepticism) comprise the ethos of a contemporary scientist (Merton 1942).

Still in the context of science education, it should be kept in mind that the dialectical nature of scientific investigation forces itself upon my analysis of epistemological obstacles. Thus, on one hand, the objective of this book is to help prospective physiological psychologists obtain a solid base in physiological psychology by adding to their formal education some knowledge of the worldview of physiological psychology. After all, it is only through the assimilation of the scientific worldview and the scientific facts and methodologies that a person becomes a scientist. On the other hand, progress (which is the major distinctive characteristic of science) is obtained by refuting or refining previous knowledge. Consequently, progress is often due to non-conformists, to students who failed to assimilate the rules or refused to follow them. This means that I do not expect any reader to accept every argument in this book. To the dispair of single-minded educators, the bottom line of science education ends up being something like this: "You must learn these rules in order to become a scientist; but if you learn them too well you will be only a mediocre scientist." A necessary feature of the dialectical process is that a new synthesis is obtained at the expense of the denial of a previous thesis.

As a contribution to philosophy of science, this book has obviously modest goals. For one, no special effort was made to produce an exhaustive list of epistemological obstacles to the development of physiological psychology. Also, other important topics in the philosophy of a science (such as the rigorous description of the ontological lexicon employed by that science, or the detailed analysis of the mechanisms responsible for the generation of new ideas and assimilation of unpredicted discoveries) were not addressed at all in this book. Finally, no attempt was made to evaluate the applicability of the principles found in physiological psychology to other life sciences or other experimental sciences in general. The limited scope of the book may turn out to be its major asset, however. A concise, well-focused monograph is less likely to contain unjustified generalizations and more likely to attract the attention of busy readers who cannot afford to dedicate too many hours to any single book.