Infant-directed versus adult-directed speech as signals for faces

The effectiveness of infant- and adult-directed (ID and AD) speech as signals for adult bees was studied. In the pairing phase of Experiment 1, 4-month-olds received 6 presentations of an ID or AD speech segment that either preceded (forward pairings) or followed (backward pairings) the presentation of a smiling face. In the summation test phase, infants received 4 novel checkerboard pattern presentations, 2 with and 2 without the speech segment. Only infants in the ID forward pairing condition exhibited significant positive summation. In Experiment 2, the differences between ID and AD forward pairing groups were replicated with different speech exemplars. In Experiment 3, an ID speech segment that was paired with a smiling or sad face elicited significant positive summation, while one paired with a fearful or angry face did not, These differences in visual responding were not accompanied by differences in infant facial affect. Ways in which ID speech may facilitate associative learning are discussed.