One of the issues of psychology is language acquisition, and different theories of how this process takes place have been offered. Each theory has its good points and its bad points, and none as yet seems to be definitive in explaining this complex learning experience. Many theorists believe that human infants are biologically programmed to be responsive to language.
Bukatko and Daehler note that the human infant from birth has a special sensitivity to the sounds made by other human beings, show a preference for human voices over other sounds, and show a preference for the voice of their mother over those of a stranger. More than this, infants respond in specific ways to small variations in the sounds human's make, especially those changes in sound that signify how one word or part of a word is distinguished from another. The smallest contrastive unit in the sound system is the phoneme, and it is contrastive for meaning with predictable phonetic variants, or allophones. The morpheme is the minimal unit of meaning, though some phonemes may be morphemes. As early as two days of age, infants show that they are responsive to phonemes from many of the world's languages and show a clear preference for speech from their own language rather than another. By the age of two months, children show the ability to discriminate vowels and can detect phonemes and vowel sounds from a variety of languages. By six and nine months of age, though, they begin to less ability to distinguish phonemes from other languages than their own and to show a preference for listening to unfamiliar isolated words form their own language (Bukatko and Daehler 219).
B.F. Skinner discusses the issue of language acquisition in his overall context of behaviorist psychology. He notes that language was acquired relatively late in the development of the human species, and this involved a remarkable change as the species' vocal musculature came under operant c...