Just as the great advances of science during the Enlightenment led to major advances in philosophy (Lecture 22), the great advances in physics and chemistry during the 19th century sparked again an interest in the mechanisms that are at work in human thought processes. This time, however, the philosophical approach soon gave way to applications of the scientific method of verification through experiment. The introduction of new instrumentation and new medicines had led to much progress in medical science, and activity in the brain was becoming accessible to physical measurement.
Although the initiative to understand the laws of thought processes, feelings and consciousness came from the medical world, the scientists had to grapple with a philosophical question first. 300 years earlier Descartes had divided the world into mind (spirit and soul) and matter (body) and declared that the two follow entirely different rules. More than one scientist of the 19th century who was determined to understand how the mind works read Descartes Discours de la méthode at some point of his or her career when their work led them to recognize the connections between muscle activity and brain activity. Because experimentation with humans was severely restricted by religious or moral arguments their experiments were mostly performed with animals. As a result they also disproved Descartes' assertion that animals do not have feelings and showed the similarity of thought processes in the brains of animals and humans.
Any scientific approach to the laws that govern thought processes has to be based on the scientific method of verification through repeatable experiment. Verification requires quantitative measurement. Charles Darwin reported very detailed verifiable observations in his book The Expression of the Emotions in Man and Animals of 1872 but could not go beyond careful description because he did not know the interior workings of the brain. It was only when Ivan Sechenov showed that brain activity is linked to electric currents and introduced electrophysiology that quantitative measurements of thought processes became possible. In 1863, four years after Darwin's publication of The Origin of Species, Sechenov published Reflexes of the Brain as a series of articles that defined thought and emotion as reflexes to outer stimulants:
Reflexes are usually understood as having three parts. They begin in a receptor organ and link through its respective centripetal ("afferent") nerve with the brain; they continue as brain activity in the central nerve system itself; and they conclude with the activation of an executive organ through its centrifugal ("efferent") nerve. Sechenov extended this to thoughts, which he described as "inhibited" reflexes, ie reflexes in which the third element of the chain is suppressed.
The question how parts of a reflex can be suppressed and how voluntary decisions relate to reflexes was addressed with outstanding success by Ivan Pavlov. Darwin in his Expressions of Emotions had already studied what he called "useful associated habits." Pavlov invented an experimental procedure to measure the efficiency of such "useful" associations and developed the theory of conditioned reflexes. His starting point was the assumption that higher animals and humans have three basic "unconditioned reflexes": the sexual instinct, the food instinct and the defence instinct. He based his assumption on objective observation, such as, for example, the automatic defence reflex when an object approaches one's eye.
Pavlov's experiments were based on the food instinct of dogs, which provided him with a method for the exact measurement of reflexes. Expectation of food is accompanied by saliva production, an unconditioned reflex (instinct) of the salivary gland. By inserting a thin tube into the duct of the salivary gland of a dog Pavlov could quantify the intensity of the salivation reflex as the number of saliva drops produced. In a series of experiments that lasted several years Pavlov developed his theory of conditioned and inhibited reflexes. He showed that a dog can be made to salivate by starting a metronome, ringing a bell or any other association with food to which the dog had been trained. He demonstrated that conditioned reflexes (the association of an event with another event, such as the ringing of a bell as an indication of food) can be made to disappear if the two events are no longer experienced in association. Being a neurosurgeon by training he proved that conditioned reflexes are established through connections in an area of the brain that is different from the area responsible for unconditioned reflexes (instincts).
Pavlov's research also established the mechanism for the suppression of normal reactions or "inhibition." If the initial stimulus (ringing of a bell etc) that established the conditioned reflex is later associated with a negative experience (acid is dropped on the dog's tongue) the stimulus no longer leads to salivation. Like conditioned reflexes, inhibited reflexes can be unlearnt by establishing a new association of food with a pleasant event. If, however, the negative association is sufficiently strong, the inhibition can continue even when no negative experience follows the stimulus; the dog then refuses to take food under all circumstances, and the inhibition can lead to death through starvation.
Pavlov's research results had immense implications for the understanding of the physiology of the brain as well as for the understanding and treatment of mental illnesses. His experimental approach was based on the simple experiment, ie an experiment that isolates the cause-effect relationship of a single process as much as possible from other factors and eliminates all other possible influences on the result through careful control of the experimental set-up. To avoid distraction and interference from the environment Pavlov's dog experiments were eventually performed in sound-proof chambers and controlled through leads and levers from outside.
The researchers that went to the greatest lengths in excluding all extraneous factors and became known as the behaviourists worked mainly in the USA during the first decades of the 20th century. They designed experiments that produced quantitative measures of the behaviour of test animals under a range of tightly controlled conditions. A typical example is the study of learning processes through trial and error, performed mostly with rats or mice. In such an experiment a hungry animal enters a system of passages that lead to a number of boxes, one of which contains food. The researcher measures the time it takes the animal to find the food in repeated trials. The experimental result can be graphed, and the obtained numerical relationship can be compared with mathematical relationships derived from models.
The first "learning by trial and error" experiments were made in the USA from 1896, at the same time when Pavlov developed his technique for the measurement of conditioned reflexes. (Spence, 1956) The range of possible learning experiments is obviously huge. Researchers in the USA favoured arrangements where the experimental set-up (the "environment") does not contain a direct stimulus. German researchers that became known as the Gestalt psychologists preferred maze arrangements where the food is visible as a stimulus for learning and the learning process consists of finding the correct detour to reach the food. It is clear that the two experimental situations involve very different intellectual decisions and therefore very different brain activity. Yet another situation frequently employed requires the activation of levers, the pulling of ropes or other activity before the food can be reached and therefore combines basic selective learning (finding the correct box in a group of otherwise identical boxes) with the acquisition of other skills.
Beginning in the 1930s behaviourists tried to isolate the to-be-learned response from other environmental or stimulating effects as much as possible. In the learning experiment the arrangement now consisted of only a single runway, leaving the animal only the choice of moving forward or not moving at all. In addition the lever that had to be pressed to get to the food was made very conspicuous, and the only activity available to the animal besides moving along the runway was to press it. On the first trial it is often even smeared with a bit of wet food.
Such experiments are clearly based on the scientific principle - used with much success in physics and chemistry - to proceed from the simple situation to the more complicated one. As "trivial" as they may seem, they still produce data that can be compared with models of brain function and prove the models correct or wrong. But they provide little or no information about the laws of nature that control the process of conscious decision-making. The situation of the behaviourist can be compared with that of the astronomer who collects observations on the movement of the planets and discovers Kepler's Laws but still has to discover gravity. to advance to an understanding of gravity Newton had to formulate a theory and proceed to its verification through experiment and observation.
Researchers generally agree that the branch of science that aims to understand the laws of conscious decision-making is called psychology. Less agreement exists how psychology should be defined. The position of the behaviourist is clear in that regard:
This very limited view of processes involved in consciousness allowed the collection of much observational data but made it difficult to advance to a general framework of thought processes. Pavlov, too, emphasized experimentation based on the scientific method but did not negate the need for hypothesis-building and testing for psychical processes:
During the last decade of his life - he had already passed his 70th birthday - Pavlov applied his theory of instincts, conditioned and inhibited reflexes to the scientific analysis of practical problems of psychiatry (the branch of medicine concerned with the diagnosis, treatment and prevention of mental disorders). He considered neuroses medical conditions produced by particularly strong inhibitions, which according to his physiological work had to be caused by connections established in the brain through conditioning.
An early issue in the study of consciousness was the question whether language is a necessary condition for thought. Pavlov did not delve deeply into this problem, but he experienced his "shift from purely physiological to so-called psychical questions" while experimenting with dogs, which suggests that consciousness can exist outside language. Other observations from the animal world demonstrate clearly that thought does not require the ability to speak. A fly will bump into a window pane for hours in vain attempts to leave a room; a monkey attempting to reach a fruit or a squid trying to reach into a crevice will abandon a method if it does not work after a few attempts and try something else instead. The decision to change tactics requires conscious thought, and observations show that different animal species are capable of conscious thought to different degrees.
The question how the ability to speak influences conscious thought was studied scientifically by Lev Vygotskij. in a long series of experiments Vygotskij watched children from different age groups communicate with each other during play and in class, asked them to complete sentences that ended with "because" or "although" and studied mentally handicapped children. This allowed him to demonstrate that the ability to think and to speak goes through distinct stages and that in every stage language influences conscious thought just as much as the increasing ability to think forms the language. His studies showed that language and the capability of systematic thought go through three stages and that the outcome of each stage is retained through adult life:
Vygotskij's conclusion was that, although conscious thought is possible and does exist without language, the ability to express oneself through language strongly enhances the ability to grasp the world through conscious thought. Based on his findings Vygotskij developed a psychology of education: Given that the intellectual development of children goes through the three stages just described, the role of the teacher can only be to assist the students in their passage by making the transitions from one stage to the next easier and by exploiting the students' intellectual abilities to the fullest at every stage. The young Soviet Union initially built its new school system on Vygotskij's research and established an institute for disabled children under his leadership.
In the USA and Europe ideological opposition against communism meant that Vygotskij's work remained unknown for half a century. As a result of this self-imposed isolation the USA saw the rise of the "Sapir-Whorf hypothesis" promoted by Benjamin Lee Whorf, who claimed that thought is determined by language and that people who speak different languages think differently; in other words, the structure of the langauage determines patterns of recognition. It is now clear that the brain structure of the species Homo sapiens is not determined y the language of the individual of the species. There can be little doubt that Whorf could have avoided his errors would he have known of the research that was going on in the USSR. Vygotskij's work has only been discovered by the West in the 1990s and has gained growing influence among educators ever since.
While Pavlov, Vygotsky and the behaviourists defined and approached psychology in different ways, they agreed that psychology should be an exact science. This was not necessarily the position of everyone in the West concerned with the problem of consciousness. In the 19th century Herbert Spencer had planned his Principles of Psychology as the first volume of an encyclopaedia called Synthetic Philosophy. By the turn of the century psychology had already gained a wide following but had barely advanced as a science; the American psychologist William James called it "only the hope of science."
At the same time when Pavlov and Vygotsky laid the scientific foundations of psychology, a very different school of psychology was established by Sigmund Freud in Vienna. Freud also defined psychology as a science but showed only faint interest in experiments for the verification of his theories. Freud, like Pavlov, started from a set of basic instincts but accepted only two, "Eros" (which in Freud's definition includes both the sexual instinct and the self-preservation instinct, comparable to Pavlov's defence instinct) and the "destructive instinct" or "death instinct."
When Freud summarized his system of psycho-analysis shortly before his death he said that he arrived at the definition of the two basic instincts "after long hesitancies and vacillations." (Freud, 1940) Unlike Pavlov, who could demonstrate the existence of his three basic instincts through very basic and simple laboratory experiments, Freud derived his basic instincts from observation of human behaviour in the natural world. ("We have arrived at our knowledge of this psychical apparatus by studying the individual development of human beings.") His observations were, however, sufficient to allow him to construct a theory of behaviour by distinguishing three "psychical provinces or agencies":
According to Freud's theory the instincts constantly come into conflict with each other in daily life. To avoid displeasure the ego makes one instinct momentarily inoperative by channelling its energy into another instinct or suppressing its energy altogether. This operation is usually not achieved consciously. A large responsibility for suppression falls on the super-ego, which prescribes civilized behaviour and thus poses a severe constraint on the destructive instinct. But suppression of instincts causes neurosis, so "it is easy, as we can see, for a barbarian to be healthy; for a civilized man the task is hard." (Freud, 1940)
Freud was primarily a practitioner and used his theories for the treatment of patients. The method of psycho-analysis he developed for that purpose consisted in bringing suppressed instincts into the open, identifying the events that led to the suppression and neutralizing them by going through the experience again but in a conscious manner. Under normal circumstances people fear nothing more than being made aware of their suppressions. But they let go of such inhibitions in dreams. The interpretation of dreams is therefore an important tool of Freud's treatment method.
Freud's reliance on patient histories as scientific data and his tendency to develop sweeping theories without further testing of his assumptions led him to build a sprawling theoretical edifice. He began to emphasize Eros at the expense of all other drives and to explain all human development as a result of sexual suppressions. While he has to be credited with the discovery of the role of child sexuality, his conclusions are still much debated. The same is true for his emphasis on the love/hate relationship between father and mother on one side and sons and daughters on the other.
Freud's propensity for theoretical edifice-building not only brought him further and further away from scientific psychology, it also influenced others who were caught in the ideological confrontation of the time and even more inclined towards speculation. It has to be remembered that the period between the World Wars was not only a time of competition between capitalism and the new socialist Soviet Union; the two economic systems were also associated with ideologies and superstructures that competed for the heads and minds of people. Marxism had declared the end of all religion and the USSR had established materialism - that all facts of nature including the human mind and human history follow natural laws - as the officially prevailing thought and consequently given science a prominent place in the country's development.
The new understanding of science made its impressive appearance at the International Congress on the History of Science held in London in 1931. It was attended by delegates from twenty countries. The Soviet Union had sent eight scientists, who gave presentations such as The Social and Economic Roots of Newton's 'Principia'. Such attitude to the history of science was strikingly new to the audience. One Soviet paper was ruled out of order because it dealt with the social roots of Soviet electrical industry and its future development - the conference organizers were of the view that the future cannot be part of history. (Crowther, 1967)
The new scientific psychology that grew from the physiology of Sechenov and Pavlov arose only a few decades before the October Revolution. The materialism of the USSR gave it a strong boost and created ideal conditions for Vygotskij's studies. It also brought psychology into the centre of ideological controversy and continued to shade peoples judgement for decades. Pavlov, who was never a communist and could level the most biting criticism at the Soviet government, was always aware of the convergence between his scientific position and the materialism of the government that placed science into a position of prominence not experienced since Peter the Great. (Lecture 23) Six months before his death he said that "formerly science was divorced from life and alienated from the people, but now ... the whole nation respects and appreciates science."
Pavlov did not share Freud's speculations. While he did not agree with Freud's theory of collision between id and ego, he raised no objections against Freud's ideas of inhibition and suppression, as long as they related to the establishment and breaking of connections in the brain. Frolov (1937) relates an experiment in which a dog had acquired an inhibition to food at the combined sound of a trumpet followed by the ticking of a metronome. The inhibition was so strong that it could not be broken by any other positive association with food - the dog was in danger of starving to death. A psychiatrist working in the laboratory at the time was attracted by Freud's psychoanalysis, and discussions with him gave the experimenters the idea that the dog should be taken back to the primary experience responsible for the inhibition. They repeated the experiment, but this time the trumpet and the metronome were combined with the offering of food. Within two days the dog was eating again.
This example of healing through psychoanalysis is particularly instructive because the history of the experiment was known in every detail and it was therefore easy to return to the original inhibition. In most cases the psychologist is confronted with a fully developed inhibition and has to extract the initial inhibiting factor from interviews with a resisting patient and reports of dreams. The example of the dog is also instructive because Pavlov's experiments always related to the building and breaking up of temporary connections in the brain, not to assumed collisions of the dog's id and ego.
In the west Freud's psychoanalysis attracted intellectuals of different persuasion. The Swiss psychologist Carl Jung collaborated with Freud for five years but became uneasy with Freud's increasing emphasis on sexuality. He turned to philosophical conservatism that brought him close to the ideology of German National Socialism and developed a psychiatry based on spirituality and religion.
The combination of Freudian theory of sexuality with the revolutionary questioning of taboos characterized the psychoanalytical work of Wilhelm Reich. It led him from studies of the human character and the psychology of mass movements (as observed in Nazi Germany) into pseudo-science and charlatanry. Reich shared the fate of other psychologists who had to flee the Hitler regime. In the USA he started a company that sold "orgone accumulators", devices that according to him could attract and accumulate energy from space. He was persecuted by the Food and Drug Administration of the USA and died in jail.
Reich's fate is not the most honourable episode in the history of the USA. His "orgone theory" was clearly pseudo-science; but pseudo-science is not usually a punishable crime. If his orgone accumulators did in fact do actual harm to people he could have been prosecuted for causing bodily harm or other offences punishable under normal law. The Food and Drug Administration decided instead to burn all his books. It did this twice, in 1954 and again in the 1960s. The burning of books is one of the worst violations of freedom of thought. Responsible governments have regulations and laws for publications to protect the public interest while maintaining the right of the individual to freedom of choice. The burning of Reich's books can only be explained as a result of ideological confrontation - Reich's combination of socialist ideas with sexual liberty and "free love" was not acceptable to the USA of the 1950s and 1960s.
Crowther, J. C. (1967) The Social Relations of Science, revised edition. The Cresset Press, London.
Freud, S. (1940) Abriß der Psychoanalyse. Internationale Zeitschrift für Psychoanalyse Imago 25 (1), 7 - 67. English translation An Outline of Psycho-Analysis translated and newly edited by James Strachey (1969) W. W. Norton & Company New York.
Frolov, Y. P. (1937) Pavlov and his School; The Theory of Conditioned Reflexes. Kegan Paul, Trench, Trubner & Co. Ltd. Carter Lane E.C.
Pavlov, I. P. (1928) Lectures on Conditioned Reflexes, Twenty-five Years of Objective Study of the Higher Nervous Activity (Behaviour) of Animals; volume one translated and edited by W. H. Gantt. Lawrence &Wishart, London
Sechenov, I. (1876a) The Physiology of Growth Processes, quoted from Frolov (1937).
Sechenov, I. (1876b) Reflexes of the Brain, quoted from Frolov (1937).
Spence, K. W. (1956) Behaviour Theory and Conditioning. Yale University Press, New Haven.
Watson, J. B. (1913) Psychology as the behaviorist views it. Psychological Review 20, 158 - 177.