Infants' expectations about the recipients of infant-directed and adult-directed speech

Across cultures, adults produce infant-directed speech (IDS) when addressing infants. We explored whether infants expect IDS to be directed at infants and adult-directed speech (ADS) to adults. Infants from Spain and Turkey (12-15 months) watched animated videos with geometric figures, where one adult figure talked to an infant or another adult figure, while they were gazing at each other (Experiments 1 and 2). In some events, the adult figure addressed the infant figure with IDS, or the other adult figure with ADS (congruent); and in others, the same adult figure addressed the other adult figure with IDS or the infant figure with ADS (incongruent). Both groups of infants showed greater looking at incongruent than congruent events. This preference disappeared when the two figures gazed away from each other (Experiment 3). Thus, by 12 months of age, infants have nuanced expectations that different speech registers such as IDS and ADS are appropriate for addressing different recipients in third-party communicative contexts.