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Shared perceptual processes in phoneme and word perception: Evidence from aphasia
No full textIntroduction
Dissociations between preserved word recognition with impaired phoneme perception have long been noted (e.g., Blumstein, Cooper, Zurif & Caramazza, 1977; Miceli, Gainotti, Caltagirone, & Masullo, 1980). This dissociation is surprising given the assumption that word perception depends on phoneme perception. Consequently, some researchers have claimed that different perceptual processes are involved in phoneme and word perception (Blumstein et al., 1977) and that there are two routes for speech perception – one sublexical and one lexical (Hickok & Poeppel, 2001).
An examination of prior findings indicates, however, that perceptual discriminability of targets and distractors has often not been closely matched across the phoneme and word perception tasks (e.g., Blumstein et al., 1977). The present study revisited the issue of separate processes for phoneme and word perception using tasks with closely matched perceptual demands.
Method
Eight individuals with aphasia were tested on auditorily presented consonant discrimination, word discrimination, and lexical decision tasks using natural speech tokens. In the word discrimination task, subjects made same/different judgments to single syllable words that differed by one distinctive feature in either the initial or final phoneme (e.g., pat-bat, voicing), with one item spoken by a male and one by a female. To create the consonant discrimination stimuli, the initial or final phoneme of the word was deleted (e.g., /pæ/-/bæ/). The lexical decision task presented single spoken stimuli, using the words from the discrimination task and non-words created by changing a single distinctive feature of the word stimuli (e.g., bat-bap, place). To compare to prior studies, scores are also reported on auditory word recognition from the Western Aphasia Battery (WAB; Kertesz, 1982), which does not include phonologically close distractors, and on a picture-word matching task (PWM) with phonologically related distractors differing from targets by more than one distinctive feature.
Results and Conclusions
Replicating previous studies, performance on the two word recognition tasks without closely matched distractors (WAB and PWM) was at ceiling for some subjects with impairments on consonant discrimination (see Figures 1a/1b). However, as shown in Figures 1c/1d, for word processing tasks matched in phonological discriminability to the consonant discrimination task, scores on consonant discrimination and word processing were highly correlated, and no individual demonstrated substantially better performance on word than phoneme perception. One patient demonstrated worse performance on lexical decision (d’ = .21) than phoneme perception (d’ = 1.72), which can be attributed to impaired lexical or semantic processing. These data argue against the hypothesis that phoneme and word perception rely on different perceptual processes/routes for processing, and instead indicate that word perception depends on perception of sublexical units
Evaluating proposed dorsal and ventral route functions in speech perception and phonological short-term memory: Evidence from aphasia
No full textIntroduction
Researchers have reported patients who perform substantially better on lexical than sublexical perception tasks (e.g., Miceli, Gainotti, Caltagirone, & Masullo, 1980). These findings challenge claims that lexical perception depends on sublexical perception (e.g., McClelland & Elman, 1986), leading to proposals of separate sublexical (dorsal) and lexical (ventral) routes in speech perception (dual route models; e.g., Hickok & Poeppel, 2000; Majerus, 2013). However, prior studies have not closely matched the discriminability of the sublexical and lexical stimuli. Further, dual route models claim that phonological short-term memory (pSTM) depends on perceptual dorsal route regions, including a sensory-motor interface that translates sensory representations into motor representations used in rehearsal (e.g., Hickock & Poeppel, 2000; Ravizza et al., 2011). In contrast, traditional models of pSTM assume a phonological maintenance buffer separate from perceptual regions (Martin & Breedin, 1992). The current study addressed shortcomings of the prior perception studies using sublexical and lexical stimuli closely matched in discriminability. Performance on these tasks was related to pSTM to determine the extent to which impairments in pSTM are predicted by speech perception deficits.
Method
Thirteen individuals with aphasia completed auditorily presented speech perception tasks using natural speech tokens (syllable discrimination, word discrimination, lexical decision, and picture-word matching) and a pSTM task (digit matching). For word discrimination, subjects made same/different judgments to pairs of monosyllabic words differing by one distinctive feature in the initial or final phoneme (e.g., pat-bat). For syllable discrimination stimuli, the initial or final phoneme of the word was deleted (e.g., /pæ/-/bæ/). Words from the word discrimination task were used in the lexical decision task and non-words were created by changing a single distinctive feature of one phoneme (e.g., bat-bap). For picture-word matching, patients made same/different judgments to word and picture pairs that matched or differed by one distinctive feature of the initial or final phoneme (e.g., word: “bear”, picture: pear). To provide a comparison to prior studies, a word discrimination task was also created where words differed by three distinctive features in the initial or final phoneme (e.g., bat-sat).
For digit matching, participants judged whether two lists of digits were the same or different where the non-matching lists differed in the order of two adjacent digits.
Results and Conclusions
When the lexical and sublexical stimuli were matched in discriminability, scores were highly correlated and no individual demonstrated substantially better performance on lexical than sublexical perception (Figures 1a-c). However, when the word discriminations were easier (as in prior studies; e.g., Miceli et al., 1980), patients with impaired syllable discrimination were within the control range on word discrimination (Figure 1d). Finally, digit matching showed no significant relation to perception tasks (e.g., Figure 1e). Moreover, there was a wide range of digit matching spans for patients performing well on speech perception tasks (e.g., > 1.5 on syllable discrimination and digit matching ranging from 3.6 to 6.0). These data fail to support dual route claims, suggesting that lexical processing depends on sublexical perception and suggesting that phonological STM depends on a buffer separate from speech perception mechanisms
Baseline structural neuroimaging correlates of treatment outcomes in semantic variant primary progressive aphasia
No full text
Lexical processing depends on sublexical processing: Evidence from the visual world paradigm and aphasia
No full textData presented in Dial, McMurray and Martin (2019) Attention, Perception & Psychophysics
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC661595
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