No abstract

What do novice word learners know about the sound of words? Word‐learning tasks suggest that young infants (14 months old) confuse similar‐sounding words, whereas mispronunciation detection tasks suggest that slightly older infants (18–24 months old) correctly distinguish similar words. Here we explore whether the difficulty at 14 months stems from infants' novice status as word learners or whether it is inherent in the task demands of learning new words. Results from 3 experiments support a developmental explanation. In Experiment 1, infants of 20 months learned to pair 2 phonetically similar words to 2 different objects under precisely the same conditions that infants of 14 months (Experiment 2) failed. In Experiment 3, infants of 17 months showed intermediate, but still successful, performance in the task. Vocabulary size predicted word‐learning performance, but only in the younger, less experienced word learners. The implications of these results for theories of word learning and lexical representation are discussed.

Past research has uncovered a surprising paradox: although 14-month-olds have exquisite phonetic discrimination skills (e.g., distinguishing [b] from [d]), they have difficulty using phonetic detail when mapping novel words to objects in laboratory tasks (confusing "bin" and "din"). While some have attributed infants' difficulty to immature word learning abilities, the hypothesis presented herein is that infants are powerful word learners and this apparent difficulty occurs only when the referential status of the novel word is unclear. Across two experiments, 14-month-old infants (N = 44) used phonetic detail to map novel words to objects when conditions were conducive to wordreferent mapping (clear sentential contexts and word-referent training), thus revealing no fundamental discontinuity in its use from speech perception to word learning.

Can infants, in the very first stages of word learning, use their perceptual sensitivity to the phonetics of speech while learning words? Research to date suggests that infants of 14 months cannot learn two similar sounding words unless there is substantial contextual support. The current experiment advances our understanding of this failure by testing whether the source of infants' difficulty lies in the learning or testing phase. Infants were taught to associate two similar sounding words with two different objects, and tested using a visual choice method rather than the standard Switch task. The results reveal that 14-month-olds are capable of learning and mapping two similar sounding labels; they can apply phonetic detail in new words. The findings are discussed in relation to infants' concurrent failure, and the developmental transition to success, in the Switch task.

Several recent studies from our laboratory have shown that 14-month-old infants have difficulty learning to associate two phonetically similar new words to two different objects when tested in the Switch task. Because the infants can discriminate the same phonetic detail that they fail to use in the associative word-learning situation, we have argued that this word-learning failure results from a processing overload. Here we explore how infants perform in the Switch task with already known minimally different words. The experiment involved the same phonetic difference as used in our earlier word-learning studies. Following habituation to two familiar minimal pair object-label combinations (ball and doll), infants of 14 months looked longer to a violation in the object-label pairing (e.g., label 'ball' paired with object doll) than to an appropriate pairing. These results using well known words are consistent with the pattern of data recently obtained by Swingley and Aslin (2002) in which it was found that infants of 14 months look longer to the correct object when the accompanying well known word is spoken correctly rather than mispronounced. We discuss how these results are compatible with the limited resource explanation originally offered by Stager and Werker (1997).