There are very few instances of brain lateralization in other animals, although, interestingly enough, bird-song is one exception. In birds, a functioning left hypoglossal nerve is essential for the production of song.
The development of hemispheric specialization is certainly connected with the development of language as an uniquely human phenomenon. Moreover, language is not only a superior means of communication between human beings, but also an essential tool for understanding and thinking about the world. We do not necessarily think in words. The scanning and sorting of information goes on unconsciously as part of the creative process, and can certainly take place during sleep. There is no reason to confine the use of the term ‘thinking’ to conscious deliberation. But, if we are to formulate our thoughts, express them, and convey them to our fellows, we must put them into words. Although language appears to be understood by both hemispheres to some extent, formulating thoughts in words, and creating new sentences, are functions of the left hemisphere.
It is worth noting that children with lesions in the right hemisphere may be competent at reading, but poor at communicating their feelings. Their speech is often monotonous and inexpressive, lacking just those emotional/intonational aspects of speech recognized earlier as being important in communication between mothers and infants.
It is probably the case that as a listener to music becomes more sophisticated and therefore more critical, musical perception becomes partly transferred to the left hemisphere. However, when words and music are closely associated, as in the words of songs, it seems that both are lodged together in the right hemisphere as part of a single Gestalt. Since the word order of a song is fixed, the innovative verbal skills which belong in the left hemisphere are not required.
Musical gifts are multiple and not always found together in the same person. There is often a wide discrepancy between musical interest and musical talent. Many of those to whom music is immensely important struggle for years to express themselves as composers or executants without avail. Others who are auditorily gifted, as shown by musical aptitude tests, are not necessarily very interested in music. Teachers of music agree that enthusiasm for music becomes increasingly important for success as a child grows older. Musically gifted children may fail to realize their full potential because their interest in music declines.24
It is my impression, and no more than an impression, that this discrepancy between interest and talent is more often encountered in music than in other subjects. For example, those who are not mathematically gifted seldom long to be mathematicians; but musical enthusiasts often confess that their lack of musical talent is their greatest disappointment.
The discrepancy between interest in, and talent for, music may be explicable in terms of hemispheric specialization. We have already observed that critical appreciation of music is partly a function of the left hemisphere. People who score highly on a test of musical aptitude tend to show left hemisphere advantage, regardless of training.25 Perhaps emotional response to music is chiefly centred in the right hemisphere, whilst executive skills and critical analysis are functions of the left hemisphere. Sloboda quotes the case of a violinist with damage to the left hemisphere who retained some musical abilities whilst suffering impairment of others. A great deal of further research is required to establish the neurological correlates of the varied skills which music requires, but what seems certain is that there is no one centre in the brain which houses them all.
As we pointed out earlier, the language used both by philosophers and scientists is neutral and objective. It eschews the personal, the particular, the emotional, the subjective. No wonder it is principally housed in a separate part of the brain from that concerned with the expressive aspects of music. Whilst it is perfectly possible to study music from a purely objective, intellectual point of view, this approach alone is insufficient.
Any attempt to understand the nature of music must take into account its expressive aspects and the fact that the parts of the brain concerned with the emotional effects of music are distinct from those which have to do with appreciation of its structure. Recordings of blood-pressure, respiration, pulse-rate and other functions controlled by the involuntary, autonomic nervous system taken from the same subject demonstrated that, when he was completely involved with the music there were marked changes in the tracings recording evidence of physiological arousal; when, however, he adopted an analytical, critical attitude, these changes were not apparent.26
This is objective confirmation of the art historian Wilhelm Worringer’s well-known dichotomy, empathy and abstraction; categories which are just as applicable to music as to the visual arts with which he was primarily concerned.27 Worringer claimed that modern aesthetics was based upon the behaviour of the contemplating subject. If the subject is to enjoy a work of art, he must absorb himself into it, make himself one with it. But this empathic identification with the work is only one way of approaching it. The other is by way of abstraction. Aesthetic appreciation is also a matter of discovering form and order, which requires detachment from the work. These two attitudes are linked with extraversion and introversion. In individuals, one or other attitude is usually predominant and, when exaggerated, leads to mutual misunderstanding. Empathic identification with a musical work may so emotionally involve the listener that critical judgement becomes impossible. In contrast, an exclusively intellectual, detached approach may make it difficult to appreciate the music’s emotional significance. Many disputes both in psychology and in aesthetics arise because each participant claims that whichever attitude he personally adopts is the only valid one.
Although appreciation of a musical work necessarily involves perception of both form and expressive content, it is interesting that the two can be artificially separated. Many years ago, I acted as a ‘guinea-pig’ for one of my colleagues who was investigating the effects of the drug mescaline. Whilst still under its influence, I listened to music on the radio. The effect was to enhance my emotional responses whilst concurrently abolishing my perception of form. Mescaline made a Mozart string quartet sound as romantic as Tchaikovsky. I was conscious of the throbbing, vibrant quality of the sounds which reached me; of the bite of bow upon string; of a direct appeal to my emotions. In contrast, appreciation of form was greatly impaired. Each time a theme was repeated, it came as a surprise. The themes might be individually entrancing, but their relation with one another had disappeared. All that was left was a series of tunes with no connecting links: a pleasurable experience, but one which also proved disappointing.
My reaction to mescaline convinced me that, in my own case, the part of the brain concerned with emotional responses is different from the part which perceives structure. The evidence suggests that this is true of everyone. The appreciation of music requires both parts, although either may predominate on a particular occasion.
In connection with the perception of form and structure it is worth recalling that the auditory apparatus is itself primarily concerned with symmetry and closely linked with balance. The labyrinth or inner ear contains the complex vestibular organ which orients us to gravity, and provides essential information about the position of our own bodies, by registering acceleration, deceleration, angles of turn et cetera. Such internal feedback is needed if we are to be able to control our own movements and relate them to changes in the environment.
It also makes possible our upright posture. Equilibrium or balance can only be maintained if we are constantly informed about tilts of the body, backward, forward, right or left. A tilt in one direction immediately elicits a compensatory muscular reaction in order to prevent our falling and restore our balance.
From an evolutionary perspective, the vestibular apparatus antedates the auditory system which developed from it. Although the two systems remain functionally separate, the vestibular nerve and the cochlear nerve, which respectively convey information from the vestibular apparatus and the auditory apparatus, run in close parallel.
The auditory system is designed to record the nature and location of vibrations in the air, which we perceive as sounds. Experience tells us which sounds are dangerous or threatening, and which are likely to be harmless. By turning our heads so that the sound in each ear is of equal volume we accurately locate the direction of its origin. Hearing and orientation are