Of Words, Birds, Worms, and Weeds: Infant Word Learning and Lexical Neighborhoods.

George J. Hollich 1, Peter W. Jusczyk 1, & Paul A. Luce 2 1 Johns Hopkins University 2 University at Buffalo

ABSTRACT Two studies are reported that examine the effects of lexical competition in infant word learning. The first demonstrates that infants are sensitive to similarities among words, while the second finds large effects of lexical competition, despite a small benefit from pre- exposure. These results fit well with current models of spoken language recognition, many of which suggest a competitive effect for words arising from dense lexical neighborhoods. However, they also give support to models that suggest some exposure is necessary.

INTRODUCTION How specific are infants’ representations of words? Do words that sound similar to each other present any special difficulties, or benefits, in early lexical acquisition? That is, experience in encoding certain kinds of phonotactic sequences and metrical patterns could facilitate the acquisition of new word-to-world mappings. Alternatively, competition from existing lexical items that share similar phonotactic and phonetic properties could also inhibit children’s ability to encode a new item.

EXAMPLE Children who know the word, “hat,” could conceivably learn the word, “bat,” more quickly than a phonetically unrelated word because their experience with the ”-at" sound structure makes forming an acoustic package easier. On the other hand, competition from the “hat” representation, could make “bat” very difficult to learn and inherently confusable with “hat.”

The Studies Study 1: Do children notice phonological Study 1: Do children notice phonological similarities between words? Study 2: Is it easier to learn a word that sounds like many other words, or a word that sounds like few words? In all studies, the lexical neighbors were constructed of CVC non-words that differed in the initial consonant, the vowel, or the final consonant of a prototype. All lists were controlled for word phonotactics, frequency, and their relation to English lexical neighborhoods.

Sample list of neighbors. High Density Low Density –––––––––––––––––––––––––––––––––––––––––––– p^C tav pcD pawthwim weem pcG** pawngpcG** pawng peC paychfaSfahsh DcC thawchCEDcheth pcS pawshsOGsoyng ncC **nawchncC **nawch pcvpawvDICthich rcC rawchmUlmuhl pEC **pechpEC **pech pOC poychbWCbauch scC sawchkoTkoeth –– ––––––––––––––––––––––––––––––––––––––––––

Study 1 In study 1, 15-month-old infants exhibited a novelty preference away from a neighborhood target, after being familiarized in the head-turn preference procedure with twelve lists of twelve neighbors. This effect was observed regardless of whether or not the target was contained in the familiarization set. This suggests that, even by 15 months, infants are capable of detecting the neighborhood similarity among words. They also appear to be demonstrating what Sommers (1999) has called “phonological false memories.”

Figure 1: 15mo Data

Study 2 dense sparse 1) Used the head-turn preference procedure to familiarize 17- month-olds with a dense neighborhood (the high-density condition, six lists of twelve neighbors) and a sparse neighborhood (the low density condition six lists of three neighbors plus nine filler items). densesparse 2) Used the split-screen preferential looking paradigm to teach infants two new words, one was the target from the dense neighborhood, the other the target of the sparse neighborhood.

Results Word learning was significantly better in the low density condition, both in overall looking times and in infant reaction times to the targeted word. A control group, exposed to twelve lists of only filler items, performed worse than those from the low-density condition.

Figure 2: 17mo Data Mean Difference in Looking (sec)

Figure 3: 17mo RT’s Mean Reaction Times (msec)

Conclusions Infants are sensitive to lexical neighborhoods. Some exposure to lexical neighborhoods appears to facilitate an infants’ ability to form a representation of a new word. However, too much exposure appears to fatigue the system and/or introduce strong competitive effects. These effects appear at the phonological level (at least for younger infants.

Poster presented at CogSci George J. Hollich Department of Psychology, Ames Hall Johns Hopkins University Baltimore, MD Correspondence: Aug 12-14, Philadelphia, PA