Toward a biological theory of language development (General summary)
We have discussed language from many different aspects, have drawn various conclusions and offered a variety of explanations. If we now stand back and survey the entire panorama, will this synopsis suggest an integrated theory? I believe it will.
I. FIVE GENERAL PREMISES
The language theory to be proposed here is based upon the following five empirically verifiable, general biological premises.
(i) Cognitive function is species-specific.
Taxonomies suggest themselves for virtually all aspects of life. Formally, these taxonomies are always type-token hierarchies, and on every level of the hierarchy we may discern differences among tokens and, at the same time, there are commonalities that assign the tokens logically to a type. The commonalities are not necessarily more and more abstract theoretical concepts but are suggested by physiological and structural invariances. An anatomical example of such an invariance is cell-constituency-- it is common to all organisms. In the realm of sensory perception there are physiological properties that result in commonalities for entire classes of animals, so that every species has very similar pure stimulus thresholds. When we compare behavior across species, we also find certain invariances, fro instance, the general effects of reward and punishment. But in each of these examples there are also species differences. Cells combine into a species-specific form; sensations combine to produce species-specific pattern-recognition; and behavioral parameters enter into the elaboration of species-specific action patterns.
Let us focus on the species-specificities of behavior. There are certain cerebral functions that mediate between sensory input and motor output which we shall call generically cognitive function. The neurophysiology of cognitive function is largely unknown but its behavioral correlates are the propensity for problem solving, the formation of learning sets, the tendency to generalize in certain directions, or the facility for memorizing some but not other conditions. The interaction or integrated patterns of all of these different potentialities produces the cognitive specificities that have induced von Uexkuell, the forerunner of modern ethology, to propose that every species has its own world-view. The phenomenological implications of his formulation may sound old-fashioned today, but students of animal behavior cannot ignore the fact that the differences in cognitive processes (1) are empirically demonstrable and (2) are the correlates of species-specific behavior.
(ii) Specific properties of cognitive function are replicated in every member of the species.
Although there are individual differences among all creatures, the members of one species resemble each other very closely. In every individual a highly invariable type of both form and function is replicated. Individual differences of most characteristics tend to have a normal (Gaussian) frequency distribution and the differences within species are smaller than between species. (We are disregarding special taxonomic problems in species identification.)
The application of these notions to (i) makes it clear that also the cognitive processes and potentialities that are characteristics of a species are replicated in every individual. Notice that we must distinguish between what an individual actually does and what he is capable of doing. The intraspecific similarity holds for the latter, not the former, and the similarity in capacity becomes striking only if we concentrate on the general type and manner of activity and disregard such variables as how fast or how accurately a given performance is carried out.
(iii) Cognitive processes and capacities are differentiated spontaneously with maturation.
This statement must not be confused with the question of how much the environment contributes to development. It is obvious that all development requires an appropriate substrate and availability of certain forms of energy. However, in most cases environments are not specific to just one form of life and development. A forest pond may be an appropriate environment for hundreds of different forms of life. It may support the fertilized egg of a frog or a minnow, and each of the eggs will respond to just those types and forms of energy that are appropriate to it. The frog’s egg will develop into a frog and the minnow’s egg into a minnow. The pond just makes the building stones available, but the organismic architecture unfolds through conditions that are created within the maturing individual.
Cognition is regarded as the behavioral manifestation of physiological processes. Form and function are not arbitrarily superimposed upon the embryo from the outside but gradually develop through a process of differentiation. The basic plan is based on information contained in the developing tissues. Some functions need an extra organismic stimulus for the initiation of operation-something that triggers the cocked mechanisms; the onset of air-breathing in mammals is an example. These extra-organismic stimuli do not shape the ensuing function. A species’ peculiar mode of processing visual input, as evidenced in pattern recognition, may develop only in individuals who have had a minimum of exposure to properly illuminated objects in the environment during their formative years. But the environment clearly does not shape the mode of input processing, because the environment might have been the background to the visual development of a vast number of other types of pattern-recognition.
(iv) At birth, man is relatively immature; certain aspects of his behavior and cognitive function emerge only during infancy.
Man’s postnatial state of maturity (brain and behavior) is less advanced than that of other primates. This is a statement of fact and not a return to the fetalization and neotony theories of old (details in Chapter Four).
(v) Certain social phenomena among animals come about by spontaneous adaptation of the behavior of the growing individual to the behavior of other individuals around him.
Adequate environment does not merely include nutritive and physical conditions; many animals require specific social conditions for proper development. The survival of the species frequently depends on the development of mechanisms for social cohesion or social cooperation. The development of typical social behavior in a growing individual requires, for many species, exposure to specific stimuli such as the presence of certain action patterns in the mother, a sexual partner, a group leader, etc. Sometimes mere exposure to social behavior of other individuals is a sufficient stimulus. For some species the correct stimulation must occur during a narrow formative period in infancy; failing this, further development may become seriously and irreverible distorted. In all types of developing social behavior, the growing individual begins to engage in behavior as if by resonance; he is maturationally ready but will not begin to perform unless properly stimulated. If exposed to the stimuli, he becomes socially “excited” as a resonator may become excited when exposed to a given range of sound frequencies. Some social behavior consists of intricate patterns, the development of which is the result of subtle adjustments to and interactions with similar behavior patterns (for example, the songs of certain bird species). An impoverished social input may entail permanently impoverished behavior patterns.
Even though the development of social behavior may require an environmental trigger for proper development and function, the triggering stimulus must not be mistaken for the cause that shapes the behavior. Prerequisite social triggering mechanisms do not shape the social behavior in the way Emily Post may shape the manners of a debutante.