The scientific study and possible prediction of human behavior have been challenged by several authors who questioned the existence of a cause-effect relationship and even claimed that analysis of intelligent goal-seeking activities, which are so typically human, requires methodology completely different from that used in physical sciences (179). For many years, Bertalanffy (17), in agreement with last century's German idealistic philosophy, supported the view that organisms are more than the sum of their parts. He favored a new conception of man based on his faculties of symbolic expression and offered an organismal approach different from that of "hard science." Criticizing the stimulus-response paradigm, Bertalanffy identified it with the "robot model" which Koestler has called "the ratomorphic view of man" (129).

Controversy about the possible physicochemical determination of human behavior is important because it involves the concepts of free will and responsibility. Its philosophical history begins before Democritus and passes through Aristotle, Spinoza, Claude Bernard, and many other well-known authorities. In a brief and lucid review, Grünbaum (90) has outlined the four main arguments against causality of human behavior: (1) Since each individual is unique, his behavior is not predictable or amenable to causal description. (2) Human behavior is so complex that it eludes analysis of a problematic causality. (3) Human behavior is oriented toward future goals and is not determined

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by past facts as in the physical sciences. (4) The acceptance of behavioral causality and predictability would deny responsibility, remorse, and possible choice of good and evil. Grünbaum rejects these four arguments on logical and scientific bases, but the best proof that most of us believe in at least a degree of behavioral predictability is that we teach our children to talk, to use the toilet, and to live in a civilized society, and that within a range of variability we do succeed in educating them.

Modern cerebral physiology, which is fully deterministic, provides a new set of arguments. It has been demonstrated that when perception of sounds is totally blocked, the auditory neurons of the inferior colliculus are impoverished in specific chemicals such as RNA. Lights, shapes, or moving shadows presented to the eye produce specific electrical waves which can be recorded in the occipital lobes and which are causally related to the optic phenomena. Brain stimulation determines sensation, movement, or emotion depending on the activated structure. The material presented in this book includes many examples of cause-effect between ESB and behavioral responses.

Against this experimental determinism it has been argued that spontaneous behavior is different from laboratory phenomena and, more important, that the gap between neuronal physiology and mental activities is still immense. How can we relate electrical spikes or ionic changes in the cells with the reality of enjoying music, being in love, or writing a book? Are mental activities and neuronal physiology as unrelated to each other as the message of a painting and the chemical structure of colors and canvas? Kety (127) has indicated that there is no valid physicochemical model to explain the phenomena of consciousness, and little likelihood of developing one. The sensation of a blue sky cannot be understood or even described in terms of changes in the retina, or spikes traveling through the optic nerve, occipital cortex, and association areas.

To clarify this discussion let us review a classical experiment. In a cat under deep anesthesia, electrodes can be placed in the inner ear and connected with an electrical amplifier and a loudspeaker.

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speaker. The spectacular result is that if we whisper in the cat's ear, "How are you?" the loudspeaker will reproduce "How are you?" The interpretation of this phenomenon is not that the cat has learned to speak English but that its ear has worked as a microphone, transducing sound into electricity. The vibrations of the air produced by the human voice are received by the tympanic membrane and give rise to electrical signals in the cochlea which are picked up by the recording electrodes. The cochlea functions as an acoustic analyzer which generates "all or none" spikes in single nerve fibers, sending coded messages to the brain. Sensory inputs impinging on different sensory receptors like the ear, eye, or skin originate patterns of electrical signals which can be recorded at ascending levels of the central nervous system.

In the attempt to correlate physicochemical events of the brain with psychological phenomena, we must differentiate three groups of neuronal functions: (1) Basic metabolic changes are necessary to keep the nerve cells alive, receptive, and reactive. These processes, which include ionic exchange, oxidation of chemicals, and consumption of energy, are absolutely necessary but are unspecific and not directly correlated with psychological responses. They allow the traffic of signals independently of their quality. (2) A material carrier of coded signals is needed to circulate information through the central nervous system. This carrier is represented by chemical changes and electrical impulses which can be recorded, identified, and measured. Without senses, without neural conductors, or without basic metabolic activity, reception of information is not possible, but these mechanisms are to a great extent unlearned and automatic. At these levels there is no understanding of messages, and the signals have not yet been decoded. A gross similarity may be found in a record player where the pickup cartridge transforms the irregularities of record grooves into electrical patterns traveling through the electronic circuitry of the amplifier where they can be mixed, delayed, or changed in tonality. At these levels, the material carrier is formed by electrical pulses with a voltage

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which can be measured and a pattern which can be seen in the oscilloscope, even without knowing that there is a musical message. In order to perceive the notes of the melody, a suitable decoding mechanism, the loudspeaker, is necessary. One more element is needed to understand the musical sounds: a suitable sensor, a human being with previous training to recognize music. (3) The symbolic meaning of a message is not intrinsic in the object or in the material carrier. Its understanding is not provided automatically by inborn mechanisms within the brain. Recognition of messages must be learned and is related to the experiential history of each individual. When we show a pencil to a monkey, a savage, and a cultured man, the visual sensory inputs are transformed into electrical patterns and transmitted through optic pathways. In all three cases this initial process is probably comparable and the transmitted electrical signals are probably similar, but the interpretation will be different. For a monkey and for a savage, the pencil is only a little stick; but for a writer the pencil has many uses and meanings, and it conveys a multitude of associations. Symbolism is not in the pencil or in the receptive brain but in their previous encounters and relations.

The distinction between material carrier and symbolic meaning is important for the clarification of the limitations of electrophysiological studies of the brain. Even if our methodology for recording electrical codes of transmitted signals were highly sophisticated, we would only be able to detect the carrier, and not the meaning. We could identify the shape of a stick circulating in visual pathways, but not its history. Symbolism cannot be deciphered by any instrument when the reference point of past experience is unknown. The frame of reference which must be examined to capture a meaning is the individual experience stored inside the brain by means of special material carriers of information, probably stereochemical combinations of amino acids and other substances forming the nucleoproteic structure of memory traces. Symbolism is found by recalling experience from memory storage and comparing it with the received inputs.

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Two events are therefore taking place: comparative evaluation and temporal correlation. This constitutes the physiochemical basis of individual reactivity, and it is a matter of definition whether these processes are considered as material (because essential material events are involved) or as immaterial (because the processes depend on comparison and temporal correlation). It is more important to understand the terms of discussion than to decide on a definition.

The human newborn brain has, among other qualities, the capacity to learn languages, abstract thinking, and moral judgment, but not to create them. With the ideological materials received during childhood and the initial training in how to use them, a more adult brain may find new combinations and new ideas, but only in reference to information received from the outside. In each individual, conscious or subconscious understanding of messages is probably dependent upon progressive steps of chemical and electrical subcoding of sensory inputs, with the resulting creation of new material carriers and codes which activate a new series of electrical and chemical phenomena, involving constellations of specialized neurons. These ideas are hypothetical but they have the advantage of being useful working hypotheses that can be tested experimentally.

While recording of electrical activity in the brain provides information limited to the carriers, it should be expected that electrical stimulation of neuronal fields may activate intracerebral processes related to both initial material carriers and subsequent subcarriers of symbolic meaning and past experiences stored in the brain. In this way we could differentiate between the cerebral mechanisms responsible for simple transmission of inputs and for the cognitive processing of received information. At the present moment we still lack neurophysiological understanding of how we enjoy music or recognize a pencil, but at least we have methodologies and working hypotheses to investigate the problem, and already we can create musical and optic hallucinatory perceptions by direct stimulation of some areas of the brain.