Holly L. Storkel

Restructuring of similarity neighbourhoods in the developing mental lexicon.

Previous evidence suggests that the structure of similarity neighbourhoods in the developing mental lexicon may differ from that of the fully developed lexicon. The similarity relationships used to organize words into neighbourhoods was investigated in 20 pre-school children (age 3;7 to 5;11) using a two alternative forced-choice classification task. Children classified the similarity of test words relative to a standard word to determine neighbourhood membership. The similarity relationship between the test and standard words varied orthogonally in terms of type of similarity and position of overlap. Standard words were drawn from neighbourhoods differing in density. Results showed that dense neighbourhoods were organized by phoneme similarity in the onset + nucleus or rhyme positions of overlap. In contrast, sparse neighbourhoods appeared to be organized by phoneme similarity in the onset + nucleus, but manner similarity in the rhyme. These results are integrated with previous findings from infants and adults to propose a developmental course of change in the mental lexicon.

Do children acquire dense neighborhoods? An investigation of similarity neighborhoods in lexical acquisition

This study tests the claim that children acquire collections of phonologically similar word forms, namely, dense neighborhoods. Age of acquisition (AoA) norms were obtained from two databases: parent report of infant and toddler production and adult self-ratings of AoA. Neighborhood density, word frequency, word length, Density × Frequency and Density × Length were analyzed as potential predictors of AoA using linear regression. Early acquired words were higher in density, higher in word frequency, and shorter in length than late acquired words. Significant interactions provided evidence that the lexical factors predicting AoA varied, depending on the type of word being learned. The implication of these findings for lexical acquisition and language learning are discussed.

The effect of probabilistic phonotactics on lexical acquisition

The effect of probabilistic phonotactics on lexical acquisition in typically developing children was examined to determine whether a lexical or sublexical level of language processing dominates lexical acquisition. Sixty-one normally achieving 7, 10, and 13 year-old children participated in a word learning task, involving non-words of varying probabilistic phonotactics. Non-words were presented in a lecture format and recognition memory was tested following a 7 minute filled delay. Results showed that 10 and 13 year-old children recognized more high probability non-words than low probability non-words. In contrast, 7 year-old children showed no consistent effect of probabilistic phonotactics on lexical acquisition. These findings suggest that the sublexical level of processing dominates word learning during the initial phases in older children. This, in turn, raises questions about the mental representations of words and the effect of phonological knowledge on lexical acquisition in young children. Implic...The effect of probabilistic phonotactics on lexical acquisition in typically developing children was examined to determine whether a lexical or sublexical level of language processing dominates lexical acquisition. Sixty-one normally achieving 7, 10, and 13 year-old children participated in a word learning task, involving non-words of varying probabilistic phonotactics. Non-words were presented in a lecture format and recognition memory was tested following a 7 minute filled delay. Results showed that 10 and 13 year-old children recognized more high probability non-words than low probability non-words. In contrast, 7 year-old children showed no consistent effect of probabilistic phonotactics on lexical acquisition. These findings suggest that the sublexical level of processing dominates word learning during the initial phases in older children. This, in turn, raises questions about the mental representations of words and the effect of phonological knowledge on lexical acquisition in young children. Implications of these findings for children with specific language impairment (SLI) are discussed.

An online calculator to compute phonotactic probability and neighborhood density on the basis of child corpora of spoken American English.

An online calculator was developed (www.bncdnet.ku.edu/cml/info_ccc.vi) to compute phonotactic probability—the likelihood of occurrence of a sound sequence—and neighborhood density—the number of phonologically similar words—on the basis of child corpora of American English (Kolson, 1960; Moe, Hopkins, & Rush, 1982) and to compare its results to those of an adult calculator. Phonotactic probability and neighborhood density were computed for a set of 380 nouns (Fenson et al., 1993) using both the child and adult corpora. The child and adult raw values were significantly correlated. However, significant differences were detected. Specifically, child phonotactic probability was higher than adult phonotactic probability, especially for highprobability words, and child neighborhood density was lower than adult neighborhood density, especially for words with high-density neighborhoods. These differences were reduced or eliminated when relative measures (i.e., z scores) were used. Suggestions are offered regarding which values to use in future research.

Developmental differences in the effects of phonological, lexical and semantic variables on word learning by infants

The influence of phonological (i.e., individual sounds), lexical (i.e., whole-word forms) and semantic (i.e., meaning) characteristics on the words known by infants age 1.4 to 2.6 was examined, using an existing database (Dale & Fenson, 1996). For each noun, word frequency, two phonological (i.e., positional segment average, biphone average), two lexical (i.e., neighborhood density, word length) and four semantic variables (i.e., semantic set size, connectivity, probability resonance, resonance strength) were computed. Regression analyses showed that more infants knew (1) words composed of low-probability sounds and sound pairs, (2) shorter words with high neighborhood density, and (3) words that were semantically related to other words, both in terms of the number and strength of semantic connections. Moreover, the effect of phonological variables was constant across age, whereas the effect of lexical and semantic variables changed across age.

The Independent Effects of Phonotactic Probability and Neighborhood Density on Lexical Acquisition by Preschool Children

The goal of this research was to disentangle effects of phonotactic probability, the likelihood of occurrence of a sound sequence, and neighbourhood density, the number of phonologically similar words, in lexical acquisition. Two-word learning experiments were conducted with 4-year-old children. Experiment 1 manipulated phonotactic probability while holding neighbourhood density and referent characteristics constant. Experiment 2 manipulated neighbourhood density while holding phonotactic probability and referent characteristics constant. Learning was tested at two time points (immediate vs. retention) in both a naming and referent identification task, although only data from the referent identification task were analysed due to poor performance in the naming task. Results showed that children were more accurate in learning rare sound sequences than common sound sequences and this was consistent across time points. In contrast, the effect of neighbourhood density varied by time. Children were more accurate in learning sparse sound sequences than dense sound sequences at the immediate test point but accuracy for dense sound sequences significantly improved by the retention test without further training. It was hypothesised that phonotactic probability and neighbourhood density influenced different cognitive processes that underlie lexical acquisition.

A comparison of homonym and novel word learning: the role of phonotactic probability and word frequency.

This study compares homonym learning to novel word learning by three- to four-year-old children to determine whether homonyms are learned more rapidly or more slowly than novel words. In addition, the role of form characteristics in homonym learning is examined by manipulating phonotactic probability and word frequency. Thirty-two children were exposed to homonyms and novel words in a story with visual support and learning was measured in two tasks: referent identification; picture naming. Results showed that responses to homonyms were as accurate as responses to novel words in the referent identification task. In contrast, responses to homonyms were more accurate than responses to novel words in the picture-naming task. Furthermore, homonyms composed of common sound sequences were named more accurately than those composed of rare sound sequences. The influence of word frequency was less straightforward. These results may be inconsistent with a one-to-one form-referent bias in word learning.

Individual Differences in the Influence of Phonological Characteristics on Expressive Vocabulary Development by Young Children.

The current study attempts to differentiate effects of phonotactic probability (i.e. the likelihood of occurrence of a sound sequence), neighbourhood density (i.e. the number of phonologically similar words), word frequency, and word length on expressive vocabulary development by young children. Naturalistic conversational samples for three children (age 1;4-3; 1) were obtained from CHILDES. In a backward regression analysis, phonotactic probability, neighbourhood density, word frequency, and word length were entered as possible predictors of ages of first production of words for each child. Results showed that the factors affecting first production of words varied across children and across word types. Specifically, word length affected ages of first production for all three children, whereas the other three variables affected only one child each. The implications of these findings for models of expressive vocabulary development are discussed.

Planning speech one syllable at a time: the reduced buffer capacity hypothesis in apraxia of speech

This investigation examined the phonologic similarity effect among individuals with aphasia (APH), with aphasia and apraxia of speech (APH/AOS) and normal controls (NC). Participants repeatedly produced pairs of rhyming words that contrasted with respect to the featural similarity of their onsets (i.e. shared voicing and manner, shared place and manner, no shared features). Rogers and Storkel (1998) used similar word pairs, but presented them one at a time, ostensibly requiring reprogramming of pre-motor processing buffers whenever a novel word was presented. They found that phonologic similarity delayed naming. In the present investigation, a parameter remapping task was used in which both words in the pair were presented before speakers began the rapid serial productions, thus alleviating the need to reprogram the processing buffer between the first and second word. Two measures of inter-word interval duration were obtained. The APH and NC groups showed no differences in inter-word interval length betwe...

A corpus of consonant–vowel–consonant real words and nonwords: Comparison of phonotactic probability, neighborhood density, and consonant age of acquisition

A corpus of 5,765 consonant–vowel–consonant sequences (CVCs) was compiled, and phonotactic probability and neighborhood density were computed for both child and adult corpora. This corpus of CVCs, provided as supplementary materials, was analyzed to address the following questions: (1) Do computations based on a child corpus differ from those based on an adult corpus? (2) Do the phonotactic probability and/or the neighborhood density of real words differ from those of nonwords? (3) Do phonotactic probability and/or neighborhood density differ across CVCs that vary in consonant age of acquisition? The results showed significant differences in phonotactic probability and neighborhood density for the child versus adult corpora, replicating prior findings. The impact of this difference on future studies will depend on the level of precision needed when specifying probability and density. In addition, significant and large differences in phonotactic probability and neighborhood density were detected between real words and nonwords, which may present methodological challenges for future research. Finally, CVCs composed of earlier-acquired sounds differed significantly in probability and density from those composed of later-acquired sounds, although this effect was relatively small and is less likely to present significant methodological challenges to future studies.