Development of responsiveness to suprathreshold acoustic stimulation in chickens.

Observed developmental changes in a UCR to acoustic stimulation in young Hubbard?×?Hubbard chickens. Specifically, durations of distress call (peep) suppression were measured after the onsets of tones that differed in intensity and frequency in 384 newly hatched and 4-day-old chicks. Resuppression was also measured after a 6% change in the frequency of these tones, once Ss had habituated to the original tone. Data show that the suppression varied systematically as a function of age, intensity, and frequency: (a) the duration of suppression increased with increasing stimulus intensity; (b) responsiveness to high frequencies grew more rapidly over the 1st 4 days than responsiveness to low frequencies, an effect indicating a developmental gradient across frequencies with age; (c) resuppression to the 6% change in frequency increased in duration with age; and (d) young Ss suppressed vocalizations longer to loud tones in the range of their species' maternal assembly call than to other frequency–intensity combinations. These developmental trends indicate rapid changes in perceived loudness and perceptual sharpening over the first few days of postnatal life. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)