Naps promote rule abstraction in language-learning infants

Gomez, R. L., Bootzin, R. R., & Nadel, L. (2006). Naps promote abstraction in language-learning infants. Psychological Science, 17(8).

Infants accomplish an incredible amount of learning during their waking hours. However, as many parents may know, infants spend most of their day asleep. It is possible that sleep is very important for an infant’s cognitive and linguistic development. The present study investigated infant’s learning of an artificial language following either a period of sleep or wakefulness, and compared learning across groups. The results demonstrated that naps promote a qualitative change in infants’ learning.

Infants, although not yet fluent in their native language, are well on their way to acquiring language. Indeed, past research using artificial language paradigms has shown that infants are incredibly adept at uncovering the regularities within speech. In the present study, infants were familiarized with a language comprised of nonadjacent dependencies. Such a structure requires participants to track the dependencies between the first and third element, for example: pel-wadim-jic, or pel-kicey-jic. Here, the first nonsense word predicts the third, and the middle nonsense word can vary. This structure is also evident within English where there is a dependency between an auxiliary and an inflection with an intervening verb, for example: is playing.

The artificial language study was composed of 48 nonadjacent dependency strings (e.g.: pel-X-jic). Infants in the experimental condition heard each string 5 times in a familiarization phase. Infants were tested on their knowledge of strings from the familiarization phase, and novel strings that followed the same nonadjacent dependency rule. Testing took place four hours after the familiarization phase. During the four-hour break, infants either took a nap or stayed awake. Results demonstrated that infants who took a nap between the familiarization and test phase were better able to abstract the nonadjacenet dependency rule to novel stimuli. Infants who did not take a nap demonstrated memory for nonadjacent word pairs from the familiarization phase, but not novel items. It might be that infants who took a nap learned the “relationship in general” between the first and third word strings. This ability to abstract from a rule and apply it to novel situations is an essential process in language and cognitive development, and results from this study suggest that sleep may play an important role in this process.

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