Input variability is key in many aspects of linguistic learning, yet variability increases input complexity, which may cause difficulty in some learning contexts. The current work investigates this trade-off by comparing speaker variability effects on L2 vocabulary learning in different age-groups. Existing literature suggests that speaker variability benefits L2 vocabulary learning in adults, but this may not be the case for younger learners. In this study, native Englishspeaking adults, 7-8 year-olds, and 10-11 year-olds learned six novel Lithuanian words from a single speaker, and six from eight speakers. In line with previous research, adults showed better production of the multi-speaker items at test. No such benefit was found for either group of children either in production or comprehension. Children also had greater difficulties in processing multiple-speaker cues during training. We conclude that age-related capacity limitations may constrain the ability to utilise speaker variability when learning words in a new language.Learning early stages of word learning (~14 months). A surprising finding is that even if infants have apparently mastered a particular phoneme contrast in their native language they may have difficulties learning novel words which differ only in this contrast. For example, Stager and Werker (1997) found that although 14-month-olds could discriminate /b/ and /d/, they could not successfully differentiate the novel minimal pair words /bɪ/ and /dɪ/ in a word learning context. This effect has been demonstrated many times (see Werker & Curtin, 2005, for a review). (2009) demonstrated that when the novel minimal pair words (/buk/ and /puk/ in their study) were spoken by multiple speakers, infants of the same age were successful in mapping each novel minimal-pair word onto a novel object. Further studies and computational modelling suggest that this difference is due to the fact that when the words are spoken by a single speaker, consistent cues from that speaker become associated with the object and this occurs at the expense of phonetically relevant cues (Apfelbaum & McMurray, 2011;Rost & McMurray, 2010; cf. Galle et al., 2015, for evidence that the benefit of variability does not rely on multiple speakers per se, since similar effects are seen from a single speaker who deliberately varies mean pitch, pitch contour, and duration of word tokens). Note that this account assumes that word learning is an associative process in which even linguistically irrelevant cues may be incorporated into lexical representations, at least in the early stages of learning.
Critically, however, Rost and McMurrayThere is also evidence that speaker variability may benefit word learning in older children. Richtsmeier et al. (2009) taught 4-year old English-speaking children novel English nonce words (i.e., adhering to English phonology and phonotactics) associated with novel animal 5pictures. Words that had been presented in multiple voices were later repeated faster and more accurately than words that had been ...
