Katherine C. Hustad, PhD – Slide of the Week

Katherine C. Hustad, PhD - Slide of the Week

Title: Effects of target word frequency and neighborhood competition on expected intelligibility

Background: Young children (between 30 and 37 months in age) repeated single words, and these words were transcribed by listeners. We asked whether the statistical properties of the words predicted intelligibility (whether the listener correctly transcribed it). Target frequency refers to the frequency of the word in spoken speech (based on English subtitles). Neighborhood competition refers to the total frequency of a word and its neighbors (words that are 1-sound away from the target: The neighbors of “cat” would include “bat”, “cut”, “cap”, “cant”, “at”, among others.) A. There is a clear positive effect of frequency on intelligibility where more frequent words are transcribed correctly more often. B. There is a likely negative effect on neighbor competition where words from larger, more “crowded” neighborhoods are probably transcribed correctly less often. C. Dividing words by their neighborhood competition suggests that there is an interaction between frequency and neighborhood competition. Words in low-competition neighborhoods (left panel) are “big fish in small ponds”, so the benefit of increases in frequency are smaller (leading to a flatter trend line). Words in high-competition neighborhoods (right panel) benefit more from frequency, as shown by the steeper trend line.

Citation: Mahr, T. & Hustad, K. (in press). Lexical predictors of intelligibility in young children’s speech. Journal of Speech, Language, and Hearing Research.

Abstract: Purpose: Speech perception is a probabilistic process, integrating bottom‐up and top[1]down sources of information, and the frequency and phonological neighborhood of a word can predict how well it is perceived. Instead of asking how intelligible speakers are, it is important to ask how intelligible individual words are. We examined whether lexical features of words influenced intelligibility in young children. In particular, we applied the Neighborhood Activation Model (Luce & Pisoni, 1998) which posits that a word’s frequency and the overall frequency of a word’s phonological competitors jointly affect the intelligibility of a word. Method: We measured the intelligibility of 165 children between 30 and 47 months in age on 38 different words. We performed an item‐response analysis using generalized mixed effects logistic regression, adding word‐level characteristics (target frequency, neighborhood competition, motor complexity, phonotactic probability) as predictors of intelligibility. Results: There was considerable variation among the words and the children, but between‐word variability was larger in magnitude than between‐child variability. There was a clear positive effect of target word frequency and a negative effect of neighborhood competition. We did not find a clear negative effect of motor complexity, and phonotactic probability did not have any effect on intelligibility. Conclusions: Word frequency and neighborhood competition both had an effect on intelligibility in young children’s speech, so listener expectations are an important factor in the selection of items for children’s intelligibility assessment.

About the Lab: Katherine Hustad is Professor and Chair of Communication Sciences and Disorders.  Her research examines speech and language development in children with cerebral palsy, with a focus on improving treatment decision-making, clinical outcomes, and quality of life.  Visit the Wisconisn Intelligibility, Speech, and Communication (WISC) Lab for more information.

Investigator: Katherine C. Hustad, PhD

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