A visually reinforced infant speech discrimination (VRISD) paradigm is described and evaluated. Infants at two ages were tested with the new paradigm on the following speech contrasts: [sa] vs [va], [sa] vs [∫a], [sa] vs [za], [as] vs [a:z], [a:s], vs [a:z], [at] vs [a:d], [a:t] vs [a:d], [at] vs [a:t], [fa] vs [θa], and [fi] vs [θi]. The data reported are compared with data on the same speech contrasts obtained from three month olds in a high-amplitude sucking paradigm. Evidence suggesting developmental changes in speech-sound discriminatory ability is reported. Results are interpreted in light of salience of available acoustic cues and in terms of new methodological advances.

The influence of four reinforcement conditions on the auditory localization behavior of normal infants was studied. Forty-eight infants 12 to 18 months of age were assigned to one of four groups of 12 subjects each. All received 30 presentations of complex noise at suprathreshold level. After each response to the stimulus, Group 1 received no reinforcement, Group 2 received social reinforcement, Group 3 received "simple" visual reinforcement (a blinking light), and Group 4 received "complex" visual reinforcement (an animated toy animal). The two visual reinforcement conditions produced the most localization responses, followed in order by the social reinforcement and no reinforcement conditions. These results indicate that auditory localization behavior of infants is influenced by reinforcement and that the extent of this effect is related to the type of reinforcement employed.

The effect of complex visual reinforcement (animated toy animal) on auditory localization responses of infants below 12 months of age was studied. Sixty infants served as subjects and each subject received 30 presentations of complex noise at suprathreshold level. After each response to an auditory signal, one-half of the infants (experimental group) received complex visual reinforcement and the other half (control group) received no reinforcement. The experimental and control groups were further subdivided into three age groups: four months, five and six months, and seven to 11 months. Visual reinforcement produced significantly more responses (head turn) than no reinforcement for the two older age groups. There was no significant difference between the experimental and control conditions at four months of age.