Dishabituation of Visual Attention b Infant- Versus Adult-Directed Speech: Effects o r Frequency Modulation and Spectral Composition

Dishabituation of visual attention by infantand adult-directed (ID and AD) speech was investigated in four experiments. Four-month-olds received 12 10-s presentations of a checkerboard pattern with a speech segment compounded only on the ninth trial. Recovery of visual attention was observed on the compound trial in response to both ID and AD speech, but only ID speech dishabituated visual attention during the following pattern-alone retest (a Thompson-Spencer dishabituation effect, observed in the first two experiments). Synthetic analogs of these speech segments’ fundamental frequencies (Fus) elicited equivalent increases in attention on the compound trial, but neither elicited Thompson-Spencer dishabituation (Experiment 3). A synthetic version of the intact ID signal elicited Thompson-Spencer dishabituation, but synthetic stimuli simulating the Fu only, the Fu plus the first harmonic above the Fo, and the harmonics only did not (Experiment 4). These data have implications for the acoustic characteristics of ID speech that increase infant attention and arousal.