2018 Sun Session B 0900

Sunday, November 4, 2018 | Session B, Conference Auditorium | 9am

Sleep consolidates syntactically-derived verb meanings in 2-year-olds
A. He, S. Waxman, S. Arunachalam

Children are “fast mappers”, able to map a new word to meaning even on a first encounter [1]. This immediate encoding, however, is often incomplete and must be fine-tuned on future encounters [2], which requires the learner to store and consolidate the first encoding for later recall. Sleep plays an important role in memory consolidation [3-4], and in word learning specifically [5- 7]. Here, we examine the role of daytime naps in 2-year-olds’ ability to learn new verbs.

On a prominent verb-learning theory known as syntactic bootstrapping, the syntactic context in which a verb occurs is an important cue to its meaning [8]. For example, a novel verb in a transitive context (e.g., “The boy blicked the girl”) is likely to label a causative event (e.g., boy pushes girl) as opposed to a non-causative one (e.g., boy and girl wave). Two-year-olds exploit this syntactic information to acquire a new verb’s meaning, even when the syntactic information is presented in dialogues, in the absence of a relevant visual scene [9]. Importantly, they retain these representations for up to two days [9]. But a two-day delay necessarily involves sleep; thus, we do not yet know whether sleep-dependent memory consolidation plays a role in this retention. In the current study, we ask whether verb representations derived via syntactic bootstrapping are better retained after a delay including sleep as compared to a period of wakefulness.

Two-year-olds (N = 42, 25.1-29.9 months) visited the lab twice in one day (Figure 1). At Visit 1, children participated in a well-established verb-learning task [9, 11]. During Familiarization, they heard a novel verb in transitive sentences; at Test, they saw two simultaneously-presented events––a causative event (target) and a non-causative event (distractor)—and were asked to find the verb’s referent. Children returned home for a few hours; for half of the children, this period included their normal naptime, and they slept (Nap Condition), while the other half did not normally nap at this time, and they remained awake (Wake Condition). At Visit 2, children participated in the same Test as in Visit 1, but without Familiarization. This required them to recall the encodings they had formed at Visit 1. Eye gaze data during Test were entered into a mixed-effects linear regression. We found a significant interaction between Visit (1 vs. 2) and Condition (Sleep vs. Wake) (χ²(1) = 25.91, p < 0.001) (Figure 2): On Visit 1, there was no difference between conditions (p = 0.46); but on Visit 2, children who slept looked at the causative event more than those who had stayed awake (p = 0.01).

Consistent with evidence that sleep facilitates early language acquisition, this result adds evidence that sleep consolidates encodings derived from syntactic bootstrapping. In the real world, events denoted by verbs are often fleeting and not always concurrent with the utterance of the verb [11]; therefore, being able to retain syntactic information is critical to verb learning. Our results indicate that 2-year-olds can do so, and are supported by sleep-dependent memory consolidation.

References

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