The propensity to raise and vary the pitch of one's voice when addressing an infant or small child was investigated in 16 male and 16 female 21–30 yr olds, half of whom were married with children and half of whom had never married and never had children. Fundamental frequency was assessed using a sound spectrograph. Mean fundamental frequency and average variability both increased significantly over baseline when Ss were asked to imagine speaking to an infant or small child and increased significantly again when an infant or a small child was actually present. Nonparents who had little prior experience with infants modified their fundamental frequency as much as parents. Sex of speaker was not significantly related to the modification of fundamental frequency when sex differences in range of modal frequency were held constant. These modifications in vocal frequency may be attributed either to a biologically based propensity in the adult speaker or to attentional feedback from the infant or small child. (13 ref) (PsycINFO Database Record (c) 2009 APA, all rights reserved)