Auditory frequency sensitivity of

Two studies were performed where five sinusoids, 125 Hz, 250 Hz, 500 Hz, 2 kHz, and 4 kHz, were presented to babies up to 9 days old along with several no-signal trials. Although variability in responding was the key result, a flat curve was representative of the intensities required for motor responding 50% of the time across the frequencies studied. In the second experiment, fixed intensities were chosen for each signal frequency, so d’ values could be estimated. The d’s differed over frequency. Evidence is cited that responding in the auditory response cradle which was used here varies with acoustic parameters. Some reasons are suggested as to why the newborns exhibit such variability.