Understanding why infant-directed speech supports learning: A dynamic attention perspective

Infant-directed speech (IDS) refers to the suite of prosodic and structural modifications that adults use when communicating with infants, as opposed to adults. A number of theories have proposed that IDS is uniquely able to modulate infants’ attention and arousal in a way that supports real-time communication and learning. However, prior research has mainly focused on infants’ overall listening preference for IDS over adult-directed-speech (ADS) without providing a mechanistic account of how IDS optimizes moment-to-moment attention and learning. Here we draw on findings from adult neuroscience showing that sustained attention to a continuous stimulus like speech is supported by a process called entrainment, where neural oscillations become time-locked to key moments in an attended stimulus. Even though entrainment appears to be automatic in development, it may be more likely to occur when stimuli are tailored to infants’ developing cognitive abilities. We first bring together evidence from psychology and neuroscience showing that IDS supports speech processing by optimizing neural entrainment and thus enhancing time-locked attention. Then, we discuss how moment-to-moment attentional modulations in IDS are likely to accumulate across time in a way that impacts long-term language development. This framework serves to redefine ‘high-quality speech’ not as a feature of speech itself, but as a dynamic interplay between behavior, attention, and the brain. With this redefinition, developmental scientists can gain traction in understanding the beginnings and high-stakes nature of young children's highly divergent learning trajectories.