It is a curious fact about the intellectual history of the past few centuries that physical and mental development have beenapproached in quite different ways. No one would take seriously the proposal that the human organism learns through experience tohave arms rather than wings, or that the basic structure of particular organs results from accidental experience. Rather, it is taken forgranted that the physical structure of the organism is genetically determined, though of course variation along such dimensions as size,rate of development, and so forth will depend in part on external factors…
      The development of personality, behavior patterns, and cognitive structures in higher organisms has often been approached in avery different way. It is generally assumed that in these domains, social environment is the dominant factor. The structures of mindthat develop over time are taken to be arbitrary and accidental; there is no “human nature” apart from what develops as a specifichistorical product…
      But human cognitive systems, when seriously investigated, prove to be no less marvelous and intricate than the physical structuresthat develop in the life of the organism. Why, then, should we not study the acquisition of a cognitive structure such as language moreor less as we study some complex bodily organ?
      At first glance, the proposal may seem absurd, if only because of the great variety of human languages. But a closer considerationdispels these doubts. Even knowing very little of substance about linguistic universals, we can be quite sure that the possible variety oflanguage is sharply limited…. The language each person acquires is a rich and complex construction hopelessly underdetermined bythe fragmentary evidence available [to the child]. Nevertheless, individuals in a speech community have developed essentially thesame language. This fact can be explained only on the assumption that these individuals employ highly restrictive principles that guidethe construction of grammar.
46. What is the main idea of the passage?
(A) The processes of physical and mental development are totally different and must not be investigated in the same way.
(B) The development of cognitive structures such as language may be influenced by predetermined genetic controlssimilar to the genetic controls of physical development.
(C) For the most part, the structures of language are arbitrary and accidental.
(D) The uniformity of speech among individuals in one community supports the social origin of language.