Jeffry A. Coady

Uses and interpretations of non‐word repetition tasks in children with and without specific language impairments (SLI)

BACKGROUND The non-word repetition task (NRT) has gained wide acceptance in describing language acquisition in both children with normal language development (NL) and children with specific language impairments (SLI). This task has gained wide acceptance because it so closely matches the phonological component of word learning, and correlates with measures of phonological working memory, a deficit in which is hypothesized to underlie SLI. AIMS/METHODS & PROCEDURES Recent uses of the NRT seem to accept it as a measure of phonological working memory capacity in spite of the fact that researchers have consistently acknowledged that the task taps many language processes, including speech perception, phonological encoding, phonological memory, phonological assembly and articulation. This paper reviews the literature on the use of the non-word repetition task (NRT) in children with NL and children with SLI, emphasizing the component skills necessary for successful repetition. MAIN CONTRIBUTION For children with NL, discussion has focused on (1) the relationship between non-word repetition ability and vocabulary, and (2) lexical and sublexical influences on repetition accuracy. For children with SLI, discussion has focused on these factors as well, but has also considered other component skills that support non-word repetition. Researchers have examined speech perception and discrimination, phonological encoding, phonological memory, phonological assembly, motor planning, and articulation, and have found evidence that children with SLI exhibit impairments in each of these supporting skills. CONCLUSIONS Because repetition accuracy depends on lexical and sublexical properties, the NRT can be used to examine the structural properties of the lexicon in both children with NL and with SLI. Further, because the task taps so many underlying skills, it is a powerful tool that can be used to identify children with language impairments.

Phonological neighbourhoods in the developing lexicon

Structural analyses of developing lexicons have provided evidence for both childrens holistic lexical representations and sensitivity to phonetic segments. In the present investigation, neighbourhood analyses of two childrens (age 3;6) expressive lexicons, maternal input, and an adult lexicon were conducted. In addition to raw counts and frequency-weighted counts, neighbourhood size was calculated as the proportion of the lexicon to which each target word is similar, to normalize for vocabulary size differences. These analyses revealed that childrens lexicons contain more similar sounding words than previous analyses indicated. Further, neighbourhoods appear denser earlier in development relative to vocabulary size, presumably because children first learn words with more frequent sounds and sound combinations. Neighbourhood density as a proportion of the size of the lexicon then decreases over development as children acquire words with less frequent sounds and sound combinations. These findings suggest that positing fundamentally different lexical representations for children may be premature.

Sensitivity to change in perception of speech

Perceptual systems in all modalities are predominantly sensitive to stimulus change, and many examples of perceptual systems responding to change can be portrayed as instances of enhancing contrast. Multiple findings from perception experiments serve as evidence for spectral contrast explaining fundamental aspects of perception of coarticulated speech, and these findings are consistent with a broad array of known psychoacoustic and neurophysiological phenomena. Beyond coarticulation, important characteristics of speech perception that extend across broader spectral and temporal ranges may best be accounted for by the constant calibration of perceptual systems to maximize sensitivity to change.

Role of phonotactic frequency in nonword repetition by children with specific language impairments

BACKGROUND Children with specific language impairments (SLI) repeat nonwords less accurately than typically developing children, suggesting a phonological deficit. Much work has attempted to explain these results in terms of a phonological memory deficit. However, subsequent work revealed that these results might be explained better as a deficit in phonological sensitivity. AIMS This study used a nonword repetition task to examine how children with SLI extract phonological regularities from their language input. METHODS & PROCEDURES Eighteen English-speaking children with SLI (7;3-10;6) and 18 age-matched controls participated in two English nonword repetition tasks. Three- and four-syllable nonwords varied in a single phonotactic frequency manipulation, either consonant frequency or phoneme co-occurrence frequency, while all other factors were held constant. Repetitions were scored in terms of accuracy as either the percentage of phonemes correctly produced or phoneme co-occurrences (diphones) correctly produced. In addition, onset-to-onset reaction times and repetition durations were measured. OUTCOMES & RESULTS Accuracy results revealed significant group, length, and phonotactic frequency effects. Children with SLI repeated nonwords less accurately than age-matched peers, and all children repeated three-syllable nonwords and those with higher frequency phonotactic patterns more accurately. However, phonotactic frequency by group interactions were not significant. Timing results were mixed, with group reaction time differences for co-occurrence frequency, but not consonant frequency, and no group repetition duration differences. CONCLUSIONS & IMPLICATIONS While children with SLI were less accurate overall, non-significant interactions indicate that both groups of children were comparably affected by differences in consonant and diphone frequency.

Effects of contrast between onsets of speech and other complex spectra

Previous studies using speech and nonspeech analogs have shown that auditory mechanisms which serve to enhance spectral contrast contribute to perception of coarticulated speech for which spectral properties assimilate over time. In order to better understand the nature of contrastive auditory processes, a series of CV syllables varying acoustically in F2-onset frequency and perceptually from /ba/ to /da/ was identified following a variety of spectra including three-peak renditions of [e] and [o], one-peak simulations of only F2, and spectral complements of these spectra for which peaks are replaced with troughs. Results for three-versus one-peak (or trough) precursor spectra were practically indistinguishable, suggesting that effects were spectrally local and not dependent upon perception of precursors as speech. Effects of complementary (trough) spectra had complementary effects on perception of following stops; however, effects for spectral complements were particularly dependent upon the interval between precursor and CV onsets. Results from these studies cannot be explained by simple masking or adaptation of suppression. Instead, they provide evidence for the existence of processes that selectively enhance contrast between onset spectra of neighboring sounds, and these processes are relevant for perception of connected speech.

Functional Voice Testing Detects Early Changes in Vocal Pitch in Women During Testosterone Administration

OBJECTIVE To determine dose-dependent effects of T administration on voice changes in women with low T levels. METHODS Seventy-one women who have undergone a hysterectomy with or without oophorectomy with total T < 31 ng/dL and/or free T < 3.5 pg/mL received a standardized transdermal estradiol regimen during the 12-week run-in period and were then randomized to receive weekly im injections of placebo or 3, 6.25, 12.5, or 25 mg T enanthate for 24 weeks. Total and free T levels were measured by liquid chromatography-tandem mass spectrometry and equilibrium dialysis, respectively. Voice handicap was measured by self-report using a validated voice handicap index questionnaire at baseline and 24 weeks after intervention. Functional voice testing was performed using the Kay Elemetrics-Computer Speech Lab to determine voice frequency, volume, and harmonics. RESULTS Forty-six women with evaluable voice data at baseline and after intervention were included in the analysis. The five groups were similar at baseline. Mean on-treatment nadir total T concentrations were 13, 83, 106, 122, and 250 ng/dL in the placebo, 3-, 6.25-, 12.5-, and 25-mg groups, respectively. Analyses of acoustic voice parameters revealed significant lowering of average pitch in the 12.5- and 25-mg dose groups compared to placebo (P < .05); these changes in pitch were significantly related to increases in T concentrations. No significant dose- or concentration-dependent changes in self-reported voice handicap index scores were observed. CONCLUSION Testosterone administration in women with low T levels over 24 weeks was associated with dose- and concentration-dependent decreases in average pitch in the higher dose groups. These changes were seen despite the lack of self-reported changes in voice.

Nonword repetition errors of children with and without specific language impairments (SLI)

BACKGROUND Two ubiquitous findings from the literature are that (1) children with specific language impairments (SLI) repeat nonwords less accurately than peers with typical language development (TLD), and (2) all children repeat nonwords with frequent phonotactic patterns more accurately than low-probability nonwords. Many studies have examined repetition accuracy, but little work has examined childrens errors. AIMS To examine nonword repetition errors from a previously published study in terms of phonotactic probability. METHODS & PROCEDURES Eighteen children with SLI (mean age = 9;2) and 18 age-matched controls (mean age = 8;11) repeated three- and four-syllable nonwords. Substitutions were analysed in terms of phoneme frequency and phonotactic probability of the syllable containing the substitution. OUTCOMES & RESULTS Results for all children show that phoneme substitutions generally involved replacement with more frequently occurring phonemes. Also, the resulting phonotactic probability within syllables containing substitutions was greater than the probability of the targets. This trend did not differ by group. CONCLUSIONS & IMPLICATIONS These results suggest that both children with SLI and children with TLD substitute less frequent phonemes with more frequent ones, and less probabilistic syllables with higher probability ones.

Phonological and lexical effects in verbal recall by children with specific language impairments

BACKGROUND & AIMS The present study examined how phonological and lexical knowledge influences memory in children with specific language impairments (SLI). Previous work showed recall advantages for typical adults and children due to word frequency and phonotactic pattern frequency and a recall disadvantage due to phonological similarity among words. While children with SLI have well-documented memory difficulties, it is not clear whether these language knowledge factors also influence recall in this population. METHODS & PROCEDURES Sixteen children with SLI (mean age = 10;2) and chronological age-matched typically developing children (CAM) controls recalled lists of words differing in phonological similarity, word frequency and phonotactic pattern frequency. While previous studies used a small set of words appearing in multiple word lists, the current study used a larger set of words, without replacement, so that children could not gain practice with individual test items. OUTCOMES & RESULTS All main effects were significant. Interactions revealed that children with SLI were affected by similarity, but less so than their peers, comparably affected by word frequency and unaffected by phonotactic pattern frequency. CONCLUSIONS & IMPLICATIONS Results due to phonological similarity suggest that children with SLI use less efficient encoding, while results due to word frequency and phonotactic pattern frequency were mixed. Children with SLI used coarse-grained language knowledge (word frequency) comparably with peers, but were less able to use fine-grained knowledge (phonotactic pattern frequency). Paired with phonological similarity results, this suggests that children with SLI have difficulty establishing robust phonological knowledge for use in language tasks.

Children’s discrimination of vowel sequences

Children’s ability to discriminate sequences of steady‐state vowels was investigated. Vowels (as in ‘‘beet,’’ ‘‘bat,’’ ‘‘bought,’’ and ‘‘boot’’) were synthesized at durations of 40, 80, 160, 320, 640, and 1280 ms. Four different vowel sequences were created by concatenating different orders of vowels for each duration, separated by 10‐ms intervening silence. Thus, sequences differed in vowel order and duration (rate). Sequences were 12 s in duration, with amplitude ramped linearly over the first and last 2 s. Sequence pairs included both same (identical sequences) and different trials (sequences with vowels in different orders). Sequences with vowel of equal duration were presented on individual trials. Children aged 7;0 to 10;6 listened to pairs of sequences (with 100 ms between sequences) and responded whether sequences sounded the same or different. Results indicate that children are best able to discriminate sequences of intermediate‐duration vowels, typical of conversational speaking rate. Children w...

The role of spectral contrast in the perception of stop consonants following vowels and their spectral complements

The ability of listeners to recover speech information, despite dramatic articulatory and acoustic assimilation between adjacent speech sounds is remarkable and central to understanding perception of connected speech. In recent years, studies have revealed that, to some extent, auditory processes of spectral contrast compensate for assimilative effects of coarticulation. In the present studies, series of CV syllables varying acoustically in F2‐onset frequency and perceptually from [ba] to [da] were identified either following front (e.g., [i], [e]) and back (e.g., [u], [o]) vowels or following complementary nonspeech spectra. These nonspeech stimuli were harmonic spectra in which the amplitudes of individual harmonics were the inverse of their amplitudes for those same harmonics in the vowels. A prediction of a spectral contrast account is that these complementary spectra should affect perception of following sounds in a manner complementary to that for the vowels from which they were modeled. This predic...