Assessing toddlers' speech-sound discrimination

Abstract

Objective: Valid and reliable methods for assessing speech perception in toddlers are lacking in the field, leading to conspicuous gaps in understanding how speech perception develops and limited clinical tools for assessing sensory aid benefit in toddlers. The objective of this investigation was to evaluate speech-sound discrimination in toddlers using modifications to the Change/No-Change procedure [1].

Methods: Normal-hearing 2- and 3-year-olds' discrimination of acoustically dissimilar ("easy") and similar ("hard") speech-sound contrasts were evaluated in a combined repeated measures and factorial design. Performance was measured in d'. Effects of contrast difficulty and age were examined, as was test-retest reliability, using repeated measures ANOVAs, planned post hoc tests, and correlation analyses.

Results: The easy contrast (M=2.53) was discriminated better than the hard contrast (M=1.72) across all ages (p<.0001). The oldest group of children (M=3.13) discriminated the contrasts better than youngest (M=1.04; p<.0001) and the mid-age children (M=2.20; p=.037), who in turn discriminated the contrasts better than the youngest children (p=.010). Test-retest reliability was excellent (r=.886, p<.0001). Almost 90% of the children met the teaching criterion. The vast majority demonstrated the ability to be tested with the modified procedure and discriminated the contrasts. The few who did not were 2.5 years of age and younger.

Conclusions: The modifications implemented resulted, at least preliminarily, in a procedure that is reliable and sensitive to contrast difficulty and age in this young group of children, suggesting that these modifications are appropriate for this age group. With further development, the procedure holds promise for use in clinical populations who are believed to have core deficits in rapid phonological encoding, such as children with hearing loss or specific language impairment, children who are struggling to read, and second-language learners.

Figure 1

Schematic of the test set-up, including the 4’ × 5’ SoftTile interlocking foam mat that served as the response mat. This was placed on the floor of the sound booth. The mat had a wood grain pattern, except for two red pieces with circle-shaped cut-outs and a purple piece with a star-shaped cut out. The child stood on the “listening star” and a trial would begin when the child was in a ready state. The two red circles, one to the front/left and the other to the front/right of the star, displayed pictures corresponding to the no-change and change responses, respectively. In this figure, the pictures displayed (cows and frogs) were used in the teaching and training phases. A touch screen monitor was placed on a table at the child’s eye level. The touch screen monitor displayed the centering/listening cue, the complex, visual reinforcers, and the puzzle pieces. The monitor also served as a user interface for the Tester to register the child’s responses. Speakers were placed at +/− 45 degrees azimuth. Note that figure is not to scale.

Figure 2

Mean performance on the perceptually easy and hard test contrasts as a function of participant age group: Young (diamonds), Mid-Age (circles), and Old (squares).

Figure 3

Scatterplot of individual performance on the perceptually easy (/bu/ vs. /ba/) and hard (/sa/ vs. /∫a/) test contrasts. The diagonal line displays what would be expected if performance were equivalent on the perceptually easy and hard contrasts. Note that there were 3 pairs of participants who had identical scores on the perceptually easy and hard contrasts, explaining why only 27 data points are plotted in the figure.

Figure 4

Individual performance for the Young (black-filled bars), Mid-Age (unfilled bars) and Old toddlers (gray-filled bars) on the training contrast (long /u/ vs. /ga/). The children are ordered from youngest to oldest age at first testing session. At the far right are the mean (and +1 standard deviation) group data for each age group: Young (black-filled bars), Mid-Age (unfilled bars) and Old (gray-filled bars).

Figure 5

Individual performance for the Young (black-filled bars), Mid-Age (unfilled bars) and Old toddlers (gray-filled bars) on the perceptually easy test contrast (/bu/ vs. /ba/). The children are ordered from youngest to oldest age at first testing session. At the far right are the mean (and +1 standard deviation) group data for each age group: Young (black-filled bars), Mid-Age (unfilled bars) and Old (gray-filled bars).

Figure 6

Individual performance for the Young (black-filled bars), Mid-Age (unfilled bars) and Old toddlers (gray-filled bars) on the perceptually hard test contrast (/sa/ vs. /∫a/). The children are ordered from youngest to oldest age at first testing session. At the far right are the mean (and +1 standard deviation) group data for each age group: Young (black-filled bars), Mid-Age (unfilled bars) and Old (gray-filled bars).

Figure 7

Scatterplot of individual test and retest scores. The unfilled triangles display data from three toddlers who scored at ceiling at test and/or retest and the unfilled circle represents a single participant who had a 4-month delay between test and retest. The regression line was calculated with data from the toddlers who scored at ceiling and the child with the long test-retest delay excluded from the analysis.