Chap. 01 p.18-20

Chap. 01 p.18-20

The situation for primates and man in particular is not completely clear. Although regeneration is also amyotypic and coordination is either permanently disarranged or at least always remains poor, some central nervous system mechanisms seem to have developed in those forms that enable the individual to make some secondary, partial readjustment. Perhaps this new learning is based on more complex cortical activities – possibly those that are experienced by man as will – but these speculations still lack empirical evidence.
The picture would not be complete without at least a superficial reference to the sensory disarrangement brought about by extracorporeal distortions, such as vision through wearing distorting lenses or prisms. Man, and a variety of lower forms, can learn quickly to make a number of adaptive corrections for these distortions (Kohler, 1951). However, the adjustment is not complete. In adjusting motor coordination to distorted visual input, it is essential that the individual goes through a period of motor adaptation, and there is cogent evidence that this is required for a physiological reintegration between afferent and efferent impulses and not simply to provide the subject with “knowledge” of the spatial configurations (Held and Hein, 1958), (Smith and Smith, 1962). Furthermore, man’s cognitive adjustment to visually distorted environment is never complete. Subjects who wear image-inverting goggles soon come to perceive the world right-side-up (though at the beginning it was seen upside down). But even after many weeks of relative adjustment, they experience paradoxical sights such as smoke from a pipe falling downward instead of rising upward or snowflakes going up instead of coming down.
The over-all conclusion that must be drawn from the disarrangement experiments are first, that motor coordination (and certain behavior patterns dependent upon it) is driven by a rigid, unalterable cycle of neurophysiological events inherent in a species’ central nervous system; second, that larval, fetal, or embryonic tissues lack specialization; this enables these tissues to influence one another in such a way as to continue to play their originally assigned role despite certain arbitrary peripheral rearrangements. Because of this adaptability, species-specific motor coordination reappears again and again regardless of experimentally switched connections. Third, as tissues become more specialized – both in ontogeny and in phylogeny – the adaptability and mutual tissue influence disappears. Therefore, in higher vertebrates peripheral disarrangements cause permanent discoordination. Finally, with advance of phylogenetic history, ancillary neurophysiological mechanisms appear which modify and at times obscure the central and inherent theme – the cyclic driving force at the root of simple motor coordination. More complex storage devices (memories) and inhibitory mechanisms are examples.
With the emergence of more specialized brains, the nature of behavior-specificity changes. Although it would be an inexcusable over-simplification to say that behavior, in general, becomes more or less specific with phylogenetic advance, there is perhaps some truth in the following generalizations. In the lower forms, there seems to be a greater latitude in what constitutes an effective stimulus, but there is a very narrow range of possible responses. Pattern perception, for instance, is poorly developed so that an extremely large array of stimulus configurations may serve to elicit a certain behavior sequence, and thus there is little specificity in stimulability. However, the motor responses are all highly predictable and are based on relatively simple neuromuscular correlates; thus there is high degree of response specificity. With advancing phylogeny, the reverse seems to become true. More complex pattern perception is correlated with greater stimulus specificity and has a wider range of possible motor responses, that is, less response specificity. However, both of these trends in decreasing and increasing specificity are actually related to greater and greater behavioral and ecological specialization. Taxonomists will be quick to point out countless exceptions to these rules. Evolution is not so simple and can never be brought to conform to a few formulas. The statement here is merely to the effect that such trends exist and that, generally speaking, specificity both in stimulation and in responsiveness changes throughout the history of animal life.
In the vast majority of vertebrates, functional readjustment to anatomical rearrangement appears to be totally impossible. Even if the animal once “knew now” to pounce on prey, peripheral-central disarrangement will permanently incapacitate the animal from pursuing the necessities for its livelihood. If the primate order should indeed be proven to be an exception to this rule – and there is little evidence of this so far – then we would have to deal with thie phenomenon as an extreme specialization, whose details and consequences are yet to be investigated. There is much less modifiability for those coordination patterns which constitute species specific behavior than is usually realized, and we must keep in mind that most behavioral traits have species-specific aspects.
This statement is not contradicted by the great variety of arbitrary behavior that is produced by training. Pressing a bar in a cage, pecking at a red spot, jumping into the air at signal of a buzzer (in short, the infinity of arbitrary tricks an animal can be made to perform) do not imply that we could train individuals of one species (for examples, common house cats) to adopt the identical motor behavior patterns of another, such as that of a dog. Although there is perfect homology of muscles, we cannot train a cat to wag its tail with a dog’s characteristic motor coordination. Nor can one induce a cat to vocalize on the same occasions a dog vocalizes instinctively, for instance, when someone walks through the backyard. Just as an individual of one species cannot transcend the limits to behavior set by its evolutionary inheritance, so it cannot make adjustments for certain organic aberrations, particularly those just discussed. The nearly infinite possibility of training and retraining is a sign of the great freedom enjoyed by most mammals in combining and recombining individual traits, including sensory and motor aspects. The trais themselves come from a limited repertoire, are not modifiable, and are invariably species-specific in their precise motor coordination and general execution.
In Goethe’s words, addressing a developing being:
Nach dem Gesetz, wonach du angetreten.
So must du seyn, dir kannst du nicht entfliehen,
So sagten schon Sibyllen, so Propheten;
Und keine Zeit und keine Macht Zerstuchelt
Gepragte Form, die lebend sich entwickelt.*