Developmental apraxia of speech is a disorder of phonological and articulatory output processes. However, it has been suggested that perceptual deficits may contribute to the disorder. Identification and discrimination tasks offer a fine-grained assessment of central auditory and phonetic functions. Seventeen children with developmental apraxia (mean age 8:9, years:months) and 16 control children (mean age 8:0) were administered tests of identification and discrimination of resynthesized and synthesized monosyllabic words differing in place-of-articulatton of the initiai voiced stop consonants. The resynthetic and synthetic words differed in the intensity of the third formant, a variable potentially enlarging their clinical value. The results of the identification task showed equal slopes for both subject groups, which indicates no phonetic processing deficit in developmental apraxia of speech. The hypothesized effect of the manipulation of the intensity of the third formant of the stimuli was not substantiated. However, the children with apraxia demonstrated poorer discrimination than the control children, which suggests affected auditory processing. Furthermore, analyses of discrimination performance and articulation data per apraxic subject demonstrated a specific relation between the degree to which auditory processing is affected and the frequency of place-of-articulation substitutions in production. This indicates the interdependence of percep tion and production. The resuits also suggest that the use of perceptual tasks has significant clinical value.

SUMMARYA patient who already had Wernicke's aphasia due to a left temporal lobe lesion suffered a severe deterioration specifically of auditory language comprehension, subsequent to right temporal lobe infarction. A detailed comparison of his new condition with his language status before the second stroke revealed that the newly acquired deficit was limited to tasks related to auditory input. Further investigations demonstrated a speech perceptual disorder, which we analysed as due to deficits both at the level of general auditory processes and at the level of phonetic analysis. We discuss some arguments related to hemisphere specialization of phonetic processing and to the disconnection explanation of word deafness that support the hypothesis of word deafness being generally caused by mixed deficits.

The aim of this study was to assess auditory and phonetic perceptual processing of vowels in children with apraxic disorders, who demonstrated clinically with only a speech output deficit. Two experiments were conducted. In the preparatory Experiment 1 series of vowels were constructed by moving formant frequencies away from the extreme values in the vowel space in the direction of a 'neutral-vowel position'. These were presented to adults and children with no speech-language involvement. Based on identification performance low-redundancy vowels were selected, which served as the end-points of two vowel continua: /i/-/i/ and /a/-/a/. In Experiment 2 these continua were used in identification and discrimination tasks, presented to 11 children with apraxic speech problems (aged 6:11 to 9:6 years) and 12 normally developing children. The results showed poorer perception of vowels for the children with apraxic speech problems than for the control children for both continua. Identification functions indicated poorer phonetic processing; discrimination functions indicated poorer auditory processing. Furthermore, a combination of perception measures (identification and discrimination) proved to have a high differential and clinical value for the assessment of children with apraxic speech problems. The results support the view that subtle (subclinical) auditory processing deficits make part of speech output disorders.

Research on the relationship between early otitis media with effusion (OME), language impairment, and central auditory processing has been equivocal, identification and discrimi nation tasks provide us with a sensitive method of assessing speech perception on both an auditory and a phonetic level. The present study examined identification and discrimination of initial bilabial stop consonants differing in voicing by 9-year-old children with a history of severe OME. The groups studied were controlled for language impairment. The ability of these children to perceive major and minor voicing cues was examined using multiple voicing cues. Long-term effects of OME were found for both identification and discrimination performance. Children with OME produced an overall inconsistency in categorization, which suggests poorer phonetic processing. Discrimination was measured by means of " just noticeable differences" (JND).Children with early OME experience demonstrated a greater mean JND than children without early OME experience. Finally, in cases of language impairment with early OME, there was no additional deterioration of auditory or phonetic processing, it appears that either early OME or language impairment can lead to poorer perception.

The explanation of articulatory problems as an output speech disorder does not preclude the possibility that auditory processing problems are associated. Identification of brief auditory spectral cues in a place-of-articulation continuum was studied in children with articulation problems. First, it was shown that formant transition durations smaller than 20·0 ms dramatically decreased phonemic identification rates for alveolar stop consonants in control subjects. Identification tasks based on two place-of-articulation continua /pαk/-/tαk/ with F2/F3 transition durations of 52 and 20 ms were administered to groups of misarticulating children and adolescents and two control groups (children and adults). For all subject groups there was poorer phonetic processing with shorter transition durations of F2 and F3. The misarticulating subjects demonstrated poorer phonetic processing of formant transitions than did the control subjects. Shortening F2/F3 transition duration did not differentially influence perceptual behaviour between the experimental and the control groups. In determining the causal link between perception and production, an explanation of perception preceding production was favoured. It was argued that, in addition to assessing the specificity between perception and production mechanisms, assessment of perception of formant transitions may have potential as a clinical tool for evaluating phonetic processing.