Developmental norms for the acoustic reflex

Acoustic reflexes were observed in 45 infants between the ages of 12 and 36 weeks. As age increased, smaller ranges of signal levels were needed to elicit the reflex and less intensity was required, but a noise stimulus did not show age-related changes. Stimulus frequency was not a source of variation of response. The reflex arc has undergone maturation by 12 weeks of age and continues to mature to 36 weeks.