On the development of early conditioned reflexes and differentiations of auditory stimuli in infants.

Infants' sensitivity to vowel and tonal contrasts.

“…Studies of frequency discrimination in a nonspeech context, although numerous, have yielded contradictory information, with successes reported by Kasatkin and Levikova (1935), Bronshtein et al (1958), Birns et al (1965), and Bronshtein and Petrova (1967), failures by Goodman, Appleby, Scott, & Ireland (1964), Keen (1964), and Leventhal and Lipsitt (1964) and ambigious results by Bridger (1961). The variety of dependent measures employed in these studies makes comparison difficult, if not impossible.…”

Postasymptotic performance decrements during massed reinforcements.

“…Limited N, inappropriate interstimulus intervals and the near or below threshold level of the conditioned stimuli place serious limitations on the degree to which any of these data can be generalized as evidence of a performance decrement. Kasatkin and Levikova (1935), mentioned as support of performance decrements during reinforced conditioning trials by Kantrow (1937), investigated conditioned sucking responses in three human infants varying in age from 11 to 30 days at the beginning of the study. The general procedure was to present a tone two or three seconds before thrusting a lactating nipple (artificial) into the infant's mouth for a period of 15 to 30 seconds.…”

A re-evaluation of the concepts of maturation and learning as applied to the early development of behavior.

“…It seems most probable, however, that at first receptor-released acts do not make any reducedcue learning or conditioning of responses possible. The first sure evidence concerning the formation of conditioned responses now points to such a change as taking place in early post-natal life, as the studies of Mateer (41), Krasnogorsky (37,38), Bekhterev (7), D. P. Marquis (40), Aldrich (3), and of Kasatkin and Levikova (35,36) indicate. 20 It is not demonstrated that conditioning may not occur in the fetal period.…”