1. Description of the obstacle

Bachelard (1938) showed that common sense is the first epistemological obstacle to the advancement of physics and chemistry. I would like to show here that common sense is also the first obstacle to the advancement of physiological psychology (and, most likely, to the advancement of any science).

The expression common sense refers to a system of beliefs and skills shared by most people and acquired through mundane experience in absence of special education. Naturally, this concept is too broad. Any meaningful statement should refer not to the whole concept but to some component of it. After all, each component of common sense might very well be an obstacle on its own. The present discussion will be limited to three components of common sense, which will therefore constitute the first three epistemological obstacles to physiological psychology: inflexible realism (i.e., the tendency to favor primary experience), spiritualism (i.e., the acceptance of transcendental causal agents), and naive humanism (i.e., the placement of humans in a class apart from all other empirical objects).

In order to become a physiological psychologist (or any type of experimental scientist, for that matter), one often needs to abandon the world of everyday life and the sphere of primary experience. Thus, primary experience tells me that the bathroom floor is colder than the carpet in the bedroom. If I were to keep this perceptual information, I would go nowhere as a sensory psychologist. Indeed, if I use a thermometer to measure floor temperature, I notice that the temperature is the same in both rooms. Because the carpet is a better thermal insulator than the ceramic tile, my feet lose heat to the floor more slowly on the carpet than on the tile floor and, consequently, cold receptors in the skin are not stimulated to the same extent. This means that, independently of how natural and evident my uneducated experience is, it may be incompatible with scientific knowledge. It is evident, therefore, that suspicion about primary experience is a salutary attitude. Inflexible realism is an obstacle to the advancement of science.

Not much needs to be said about spiritualism. Although exceptions can be found for any rule, most educated people today would agree that ghosts do not exist, that astrology is a form of charlatanism, and that science should not be mixed with religion. The scientist as a private citizen is entitled to have his/her spiritual faith, but empirical sciences have no room for spirits. Spiritualism is an epistemological obstacle to science because it diverts research from the search for empirical phenomena.

Humanism is a much more complex concept that has been constantly changing since its origins in ancient Greece and the Renaissance. I call naive humanism that modern form of humanism that seeks an objective, although not scientific, knowledge of human nature. The requirement of non scientificity comes from the humanist's dissatisfaction with how modern science deals with issues of subjectivity and human values. This is, therefore, a straightforward epistemological obstacle: the naive humanist is openly against science and would like to obstruct its progress. I call it naive humanism because it requires shortsight not to realize that the notion of objectivity sought by the humanist comes from science (and not from some Land of the Absolutes) and, therefore, cannot be found outside of science.

2. Examples of the obstacle

Examples of common sense as an obstacle to physiological psychology can be found already at the two constituent sciences: psychology and neurophysiology. Sigmund Freud is probably the most famous psychologist of all times. Most of his work would be obstructed, however, if inflexible realism were to prevail. For example, in the sphere of primary experience there is a strong distinction between sanity and mental illness. A person is believed to be either normal or afflicted by some mental disorder. This distinction is at the basis of the rule that requires initial determination of the ability of a criminal to withstand trial. Freud always insisted, however, that sanity and pathology are merely different points in the same psychodynamic continuum (Freud 1958). Analogously, behavior therapists believe that there is no difference at all in the mechanisms by which normal behavior and deviant behavior are established (Ullman & Krasner 1965).

Still in the domain of psychology, the primary notions of natural morality and human dignity obstruct the acceptance of Freud's thesis that psychological normality consists of a particular way of dealing with (rather than excluding) the seeds of sexual perversion with which all humans are born (Freud 1949). Also, primary experience tells us that people behave this way or that way because of their thoughts, expectations, wishes, and feelings. This is incompatible with B. F. Skinner's contention that human behavior is determined instead by the contingencies of reinforcement and that wishes and feelings are collateral effects of those contingencies (Skinner 1976).

In the domain of neurophysiology, a good example is that of sensory modalities. Primary experience tells us that humans have five senses: vision, hearing, olfaction, taste, and touch. Neurophysiology tells us that, besides these five modalities, we also perceive pain, warmth, cold, pressure, rotary acceleration, and other variables (Ganong 1975). Clearly, we must be willing to go past the simplicity of primary experience in order to accept what neurophysiology takes for granted. Inflexible realism is an obstacle to the advancement of science.

A formal defense of inflexible realism was carried out by the phenomenological school of thought in the early 20th century. This is evident in Merleau-Ponty's speculative theory of behavior, according to which the study of behavior can be meaningful only if it gives priority to primary experience over everything else (Merleau-Ponty 1967). This is a straightforward case of obstruction of science where the defendant voluntarily pleads guilty.

Regarding spiritualism as an obstacle, the issue of mental illness will again provide a good example. Although the notion of mental illness itself has been the object of criticism (Foucault 1972, Szaz 1960), contemporary psychopathology certainly does not recognize spirits as causal factor of disease. However, in the Middle Ages madness was believed to be a consequence of demoniac possession, and a popular therapy consisted of beating the patient in order to induce the devil to leave the body (Coleman 1964). Naturally, this belief in demons is an obstacle to modern psychopathology.

Religions are especially strong forms of spiritualism. They certainly have more converts and more money than science. Therefore, they have a strong potential to obstruct science. Fortunately, because of the centuries-old separation between Church and State, religions have not been major sources of obstruction. It cannot be denied, however, that religion can be and has occasionally been an obstacle to the development of science (Comte 1914, Nietzsche 1920, Weber 1963). For example, the Judaico-Christian religion is supposed to have God's wisdom written down in the Holy Bible. If this is the case, God disagrees with science on many issues. Thus, in opposition to Darwin's theory of evolution, God says that all species emerged at the same time, with the exact appearance that they have today (Genesis 1, 20-25; 2, 19-20). Also, God believes it possible to load two specimens of each animal species in a rudimentary boat built by a family of inexperienced sailors (Genesis 6, 19-20; 7, 2-3), whereas science tell us that this would be impossible, as there are more than 750,000 species of terrestrial animals on earth (which would demand much more housing space, food stores, and sewage disposal than even modern technology would be able to produce).

Finally, examples should be given of naive humanism as an obstacle to the advancement of science. In its simplest form, humanism is an obstacle because it demands a radical separation between humans and all other animals. This contradicts at least three facts of life science: 1) taxonomically, the species Homo sapiens fits naturally into the family Hominidae, order Primates, class Mammalia, and so on (Lincoln & Boxshall 1987); 2) intelligence, a faculty once believed to distinguish humans from other animals, is present in almost all animals and shows a phylogenetic progression (Bitterman 1967); and 3) symbolic language, another faculty originally believed to be exclusively human, can be found in other primates as well (Gardner & Gardner 1969, Premack 1971, Rumbaugh 1980).

There are, of course, more subtle forms of humanism. For instance, Carl Rogers and other members of the so-called "third force" in psychology refuse to accept mental illness as an impurity that maculates human nature. In other words, human nature is too pure to be stained with disease, and psychotherapy should aim at helping the patient grow psychologically rather than healing his/her illness (Rogers 1977). Naturally, this attitude is an obstacle to any scientific theory of psychopathology. Supporters of anti-scientific organizations should have the right to free speech as everyone else, but scientists have the right (and the moral duty) to reject foreign threats. Other members of the third force openly oppose the concept of motivational homeostasis (which is a cornerstone in physiological psychology) because human existence is allegedly characterized by auto-transcendence rather than by the satisfaction of motivational needs (Frankl 1969, Maslow 1969). This is another obstacle to scientific psychology. Incidentally, it is curious that Maslow's theory of meta-motivations predicts that non-motivated perception should be more accurate than motivated perception (Maslow 1968), whereas empirical research shows that perceptual acuity is higher at an intermediary point within the indifference-anxiety continuum (Vernon 1970).

Physiological psychology was explicitly criticized by Frick (1971) for failing to study human behavior in a humanistic way. Naturally, this indicates a type of "ethical" humanism, but obstacles to physiological psychology may come also from a "philosophical" humanism. For instance, Sartre (1948) criticized scientific psychology for fragmenting knowledge and failing to produce a philosophically meaningful understanding of the human being. Naturally, the psychologist's response should be: "What you see are the results of my scientific research. If they do not satisfy your philosophical convictions, it is probably because your convictions are wrong."