Factors affecting the contribution and interaction of cues

By Alejandrina Cristia, Amanda Seidl, Amelie Bernard and Kris Onishi

Although studies on adults and children frequently take into account the differential experience these populations have, further research is needed to understand the cognitive and linguistic biases that may underlie the phonological learning abilities of each population. This paper aims at raising some questions about how perceptual and linguistic experience as well as other cognitive biases may underlie the relative importance that different types of cues have in each linguistic population.

Infants' weighting of diverse kinds of cues may be expected to diverge from adults' given their different perceptual abilities and input. First, infants' articulatory and auditory systems are not fully mature. Second, infants' input is qualitatively different, not only because they are frequently exposed to infant-directed speech which may emphasize different acoustic cues than ADS, but also because they may pay attention to aspects that adults normally ignore, such as visual cues. Third, infants' working memory and processing abilities are much more limited than adults, which further entails that they cannot utilize semantic information in phonological category learning, especially at the youngest ages. Nonetheless, infants learn phonological categories and distributions and are even able to do so purely on the basis of the distribution of acoustic cues, which suggests that, to some extent, other cues may not be a {\it necessary} condition for phonological learning.

Furthermore, even within those cues that are equally available to infants and adults, infants may exhibit different learning abilities due to their more limited language experience and other cognitive biases. In one set of studies, we address the question of language experience. Would learners' ability to learn a phonotactic constraint be affected by the linguistic status of the relevant acoustic cues? In order to assess the contribution of age and language experience, we tested English-learning 4- and 11-month-olds as well as English, French and Bengali adults with a constraint on nasalized vowels. The older infants and the English adults failed to learn the pattern, suggesting that they were ignoring the cues of vowel nasalization. French and Bengali adults, for whom the contrast was phonemic, were able to learn the pattern, but so were the 4-month-olds. Thus, language experience affects attention to acoustic cues and constrains phonological learning, but, at least for young infants, it is not a necessary condition for phonological learning.


A second set of studies further investigates cognitive biases that may underlie acoustic cue-weighting. We presented infants with a clause segmentation task in which we had manipulated acoustic cues such as duration, pitch and pause and found that 4- and 6-month-olds reacted differently to these manipulations. Specifically, 6-month-olds were able to succeed at the task when only some of the cues were present but exhibited a familiarity preference (associated with harder tasks), while 4-month-olds showed a novelty preference when no cues were manipulated (suggesting that the task was easy for them) but failed when any cue was absent. We interpret these results as an indication that in speech perception infants initially pursue a holistic strategy, attending to all cues, and only later become more local processors, similarly to the development of perception in non-linguistic domains.