Word learning is a fundamental part of language acquisition. Learning words from cross-situational statistics (Yu & Smith 2007) has been argued to be critical for lexical acquisition, but the resulting representations are not well understood. Here, we examine the claim from Hamrick & Rebuschat (2014) that cross-situational learning results in implicit representations. Three experiments provide evidence to the contrary. First, we establish that confidence ratings positively correlate with accuracy. By using a cover story where participants were not told to infer word meaning, only highly confident answers were above chance, contrary to what accounts of implicit memory would predict. In addition, using a deadline procedure (Voss, Bayem & Paller 2008), we found that participants performed no differently than without a deadline, contrary to predictions from implicit memory representations. In sum, we conclude that representations from cross-situational word learning are explicit.

Non-adjacent dependencies (NADs) refer to dependencies between items that are not adjacent in a sequence. Peña et al. (2002) discovered adult participants could learn the NADs of syllables in an artificial language when there were 25ms pauses before and after the NADs. Studies using videos of human body movements showed similar learning outcomes (Endress & Wood, 2011). However, participants failed to learn the NADs with respect to non-linguistic acoustic stimuli, such as tones or noises (Gebhart, Newport, & Aslin, 2009). Four experiments in this study examined the constraints on learning the NADs of visual stimuli. We propose that acquisition of the NADs requires the sequences be packed into a coherent unit, and the motor system provides the require packaging for stimuli that can be mapped onto motor representation. Implications on the acquisition of syllable NADs are discussed.

In many languages, tone (i.e., pitch patterns) is part of the phonological system; two words with the same sequences of segments can differ only in tone. Tone does not distinguish word meanings in English, so English-learning infants can ignore tone when learning words, but do they? We examined the encoding of tonal detail in word learning by monolingual English-learning 14- and 17-month-olds. Infants were habituated to a novel word with a Mandarin tone (/k´a/) paired with a novel object. Test trials alternated between the same pairing (Same), and the same object paired with the word with a different tone (/k`a/, Switch). Longer looks to the unfamiliar mapping indicate infants noticed the switch and attended to tone contrasts. Overall, neither age group discriminated the tone contrast; however, infants with larger vocabularies looked longer to the novel mapping (r=.32, p=.007), suggesting a common underlying mechanism between general word learning and tone sensitivity.

Prior research reports that children up to 3-years-oId map novel adjectives to object properties only in very limited situations (Gelman & Marlcman, 1985; Taylor & Gelman, 1988; Hall, Waxman, & Hurwitz, 1993; Klibanoff & Waxman, 1997; Waxman & Markow, 1997). Yet we know by 24-months children use adjectives. In two experiments we provide 36-month-olds (Experiment 1) and 24-month-olds (Experiment 2) with rich cross-situational and syntactic information. We show that 24- & 36-month-olds learn adjective-to-property mappings when given multiple examples of the mapping, and when object names are used. We claim that previous experiments failed to find robust adjective acquisition because at least one of these sources of information (multiple exemplars) was excluded. We also suggest that children's initial learning about the meanings of adjectives is affected by syntactic properties of the noun phrase in which they appear.