Phonemic Similarity Effect Research Articles

Phonological Feature Repetition Suppression in the Left Inferior Frontal Gyrus.

Models of speech production posit a role for the motor system, predominantly the posterior inferior frontal gyrus, in encoding complex phonological representations for speech production, at the phonemic, syllable, and word levels [Roelofs, A. A dorsal-pathway account of aphasic language production: The WEAVER++/ARC model. Cortex, 59(Suppl. C), 33-48, 2014; Hickok, G. Computational neuroanatomy of speech production. Nature Reviews Neuroscience, 13, 135-145, 2012; Guenther, F. H. Cortical interactions underlying the production of speech sounds. Journal of Communication Disorders, 39, 350-365, 2006]. However, phonological theory posits subphonemic units of representation, namely phonological features [Chomsky, N., & Halle, M. The sound pattern of English, 1968; Jakobson, R., Fant, G., & Halle, M. Preliminaries to speech analysis. The distinctive features and their correlates. Cambridge, MA: MIT Press, 1951], that specify independent articulatory parameters of speech sounds, such as place and manner of articulation. Therefore, motor brain systems may also incorporate phonological features into speech production planning units. Here, we add support for such a role with an fMRI experiment of word sequence production using a phonemic similarity manipulation. We adapted and modified the experimental paradigm of Oppenheim and Dell [Oppenheim, G. M., & Dell, G. S. Inner speech slips exhibit lexical bias, but not the phonemic similarity effect. Cognition, 106, 528-537, 2008; Oppenheim, G. M., & Dell, G. S. Motor movement matters: The flexible abstractness of inner speech. Memory & Cognition, 38, 1147-1160, 2010]. Participants silently articulated words cued by sequential visual presentation that varied in degree of phonological feature overlap in consonant onset position: high overlap (two shared phonological features; e.g., /r/ and /l/) or low overlap (one shared phonological feature, e.g., /r/ and /b/). We found a significant repetition suppression effect in the left posterior inferior frontal gyrus, with increased activation for phonologically dissimilar words compared with similar words. These results suggest that phonemes, particularly phonological features, are part of the planning units of the motor speech system.

The case for subphonemic attenuation in inner speech: comment on Corley, Brocklehurst, and Moat (2011).

Corley, Brocklehurst, and Moat (2011) recently demonstrated a phonemic similarity effect for phonological errors in inner speech, claiming that it contradicted Oppenheim and Dell's (2008) characterization of inner speech as lacking subphonemic detail (e.g., features). However, finding an effect in both inner and overt speech is not the same as finding equal effects in inner and overt speech. In this response, I demonstrate that Corley et al.'s data are entirely consistent with the notion that inner speech lacks subphonemic detail and that each of their experiments exhibits a Similarity × Articulation interaction of about the same size that Oppenheim and Dell (2008, 2010) reported in their work. I further show that the major discrepancy between the labs' data lies primarily in the magnitude of the main effect of phonemic similarity and the overall efficiency of error elicitation, and demonstrate that greater similarity effects are associated with lower error rates. This leads to the conclusion that successful speech error research requires finding a sweet spot between too much randomness and not enough data.

Motor movement matters: The flexible abstractness of inner speech

Inner speech is typically characterized as either the activation of abstract linguistic representations or a detailed articulatory simulation that lacks only the production of sound. We present a study of the speech errors that occur during the inner recitation of tongue-twister-like phrases. Two forms of inner speech were tested: inner speech without articulatory movements and articulated (mouthed) inner speech. Although mouthing one's inner speech could reasonably be assumed to require more articulatory planning, prominent theories assume that such planning should not affect the experience of inner speech and, consequently, the errors that are "heard" during its production. The errors occurring in articulated inner speech exhibited the phonemic similarity effect and the lexical bias effect--two speech-error phenomena that, in overt speech, have been localized to an articulatory-feature-processing level and a lexical-phonological level, respectively. In contrast, errors in unarticulated inner speech did not exhibit the phonemic similarity effect--just the lexical bias effect. The results are interpreted as support for a flexible abstraction account of inner speech. This conclusion has ramifications for the embodiment of language and speech and for the theories of speech production.

Inner speech slips exhibit lexical bias, but not the phonemic similarity effect

Inner speech, that little voice that people often hear inside their heads while thinking, is a form of mental imagery. The properties of inner speech errors can be used to investigate the nature of inner speech, just as overt slips are informative about overt speech production. Overt slips tend to create words ( lexical bias) and involve similar exchanging phonemes ( phonemic similarity effect). We examined these effects in inner and overt speech via a tongue-twister recitation task. While lexical bias was present in both inner and overt speech errors, the phonemic similarity effect was evident only for overt errors, producing a significant overtness by similarity interaction. We propose that inner speech is impoverished at lower (featural) levels, but robust at higher (phonemic) levels.

The influence of phoneme position overlap on the phonemic similarity effect in nonword recall

The current research examined the predictions that short-term memory models generate for the phonological similarity effect, when similarity was defined in different ways. Three serial recall experiments with consonant-vowel-consonant (CVC) nonwords are reported, where the position of the phonemes that list items shared was manipulated (i.e., shared vowel and final consonant [_VC; Experiment 1], initial consonant and vowel [CV_; Experiment 2], or the two consonants [C_C; Experiment 3]. The results show that the position of common phonemes in nonwords has differential effects on order and item information. The findings are discussed in relation to previous research into the effect of phonemic similarity on nonword recall, and modifications to current short-term memory models are proposed.

The phonological similarity effect in serial recognition

An experiment is reported examining the effect of consistent phonemic similarity among list items on memory retention in a task that is independent of overt speech production, the serial recognition task. Lists of consonant-vowel-consonant (CVC) words and nonwords were constructed such that although phoneme overlap was manipulated (i.e., shared vowel and final consonant [_VC], initial consonant and vowel [CV_], or the two consonants [C_C]), similarity remained constant. The results show that the influence of sub-syllabic mechanisms on STM performance is independent of speech production processes, and similarity in the pattern of results suggests that the same mechanisms subserve the recall of words and nonwords in STM. It is argued that the results are more consistent with psycholinguistic models than nonlinguistic models of STM, and implications for current STM models are discussed.

Word length, phonemic, and visual similarity effects in poor and normal readers

Serial order recall for visually and auditorily presented stimuli was examined in a group of 12-year-old poor readers and 7-year-old reading-age controls. With pictorial presentation, the poor readers showed a visual similarity effect, no word length effect, and a smaller phonemic similarity effect than that of controls. However, with visual presentation of printed words and with auditory presentation, poor readers showed word length and phonemic similarity effects of similar magnitude to that of controls. It is concluded that poor readers rely on visual information in tasks where the presented images are highly codable, and where verbal recoding is not obligatory, but that they will make use of phonological coding when the stimuli are not as easily codable visually in memory.

Working memory in children: A developmental approach to the phonological coding of pictorial material

This study investigated the effects of age, speech, articulatory suppression and phonemic similarity on the phonological coding of pictorial material. A serial recall task was employed to assess the effects of phonemic similarity in children aged between 3 and 11. Half of the subjects in each age group overtly named the pictures at presentation and the others remained silent. For suppression subjects who named the pictures these two tasks were performed concurrently. It was hypothesized that the effects of phonemic similarity would be affected by age and speech. This was supported, with older children showing a greater effect of phonemic similarity and subjects scoring more when allowed to overtly name the items. It was also hypothesized that the youngest children would benefit most from the overt naming of items. Analysis of the results indicated that the overt naming of items facilitated phonological recoding amongst the younger children, thereby supporting this hypothesis. The possibility that these results are due to the maturation of a phonemic store prior to the development of subvocal rehearsal processes is discussed.

Developmental Aspects of Phonemic and Visual Similarity Effects: Further Evidence in Italian Children

Phonemic and visual similarity effects were investigated in Italian children of different ages. In Experiment 1, two groups of children (mean age 5;1 and 10;3 years) were asked to recall either pictures of common objects with phonemically similar or dissimilar names, or the spoken names of the pictures. Although a similarity effect was present in older children for both words and drawings, in younger children only a tendency in the expected direction occurred. The lack of a phonemic similarity effect for spoken words was attributed to the presence of a ceiling effect. In addition, results showed a significant superior recall for words in younger children and for drawings in older ones. An additional group of 5-year-old children was tested, increasing the list length to four items. Results indicated a significant similarity effect for words but not for drawings, together with a superior recall for words. These findings, in agreement with previous results, suggest that phonological memory traces contribute to performance of younger children only when material to be recalled is in the auditory modality, whereas in older children phonological coding is independent in the input modality. In Experiment 2 the performance of 5-and 10-year-old children was compared for immediate recall of two different sets of visually similar and dissimilar drawings. Results showed a significant effect of visual similarity in younger children only, for both sets of drawings, extending previously obtained results (e.g. Hitch, Halliday, Schaaftal, & Scrhaagen, 1988) to different materials and to Italian subjects. In Experiment 3, the visual similarity effect was investigated with a delayed recall procedure in a 5-year-old group. Four delay intervals (0, 5, 10, 15 seconds) and two activities during delay (articulatory suppression and a tapping task) were considered. Results obtained indicated that the visual similarity effect is present at all delay intervals for both activities during delay; and are discussed in terms of alternative interpretations of the visual similarity effect.

Articulatory rehearsal and phonological storage in working memory.

The theoretical distinction between an articulatory control process and a short-term phonological store was supported in five experiments on immediate serial recall. In Experiment 1, articulatory suppression during the presentation and recall of auditory material abolished the word length effect but not the phonemic similarity effect. In Experiment 2, the two latter effects were found to be independent with auditory presentation. In Experiment 3, the effects of irrelevant speech and word length were found to be independent with visual presentation. In Experiment 4, articulatory suppression during the presentation and recall of auditory material abolished the phonemic similarity effect with a slow presentation rate. Nevertheless, in Experiment 5, articulatory suppression with a conventional presentation rate did not reduce the effect of phonemic similarity, even when a 10-sec interval was interposed between presentation and recall. These results indicate that the encoding, maintenance, and retrieval of spoken material within the phonological store do not depend on a process of articulatory rehearsal.

The Effects of Word Length and Phonemic Similarity in Young Children's Short-term Memory

Two experiments tested the hypothesis that word length and phonemic similarity effects in young children's recall with auditory presentation result from verbal output, and not: (1) rehearsal in the case of word length effects; (2) confusion at input in the case of phonemic similarity effects. In an auditorily presented probed recall task, where there were no full verbal output requirements, children aged five years did not show either effect. Children aged seven years showed both word length and phonemic similarity effects. It was concluded that, in children of age five, word length effects can not necessarily be taken as evidence for rehearsal, nor can the phonemic similarity effect be assumed to result from confusion at input. It is suggested that the process of saying a list verbally may cause both of these effects, and that care must be taken to distinguish input and output processes in the development of children's short-term memory.

Phonemic similarity effects and prelexical phonology

Ten experiments were conducted on visually presented Serbo-Croatian words and pseudowords, comprising phonemically similar and dissimilar context-target sequences. There were five main results. First, phonemic similarity effects in both lexical decision and naming are independent of graphemic similarity. Second, phonemic similarity need not facilitate lexical decision; the direction of its effect depends on lexicality, target frequency, and type of similarity (specifically, the position of the phoneme that distinguishes context and target). Third, phonemic similarity expedites the naming of words and pseudowords, and to the same degree. Fourth, phonemic similarity is negated in naming, but not in lexical decision, when the visually presented context and target are stressed differently. Fifth, the phonemic similarity effect occurs even when the context is a masked pseudoword. These results are discussed in terms of a model in which word-processing units are activated routinely by phoneme-processing units, and in which compositionally similar word units, when activated, inhibit one another in proportion to each's familiarity. In this model, the phonemic similarity effect in naming is based on the states of phoneme units, whereas the phonemic similarity effect in lexical decision is based on the states of word units. Overall, the results comport with an account in which phonology is computed prelexically and automatically.

Verbal short-term memory in children: The role of the articulator loop

Abstract Three experiments investigated immediate memory for drawings of familiar objects in children of different ages. The aim was to investigate the effect of articulatory suppression on word length and phonemic similarity effects. Experiment 1 showed that, with pictorial presentation, 11-year-old children showed word length effects in memory span which were abolished by suppression, whereas 5-year-olds did not. Experiment 2 provided similar results in relation to the phonemic similarity effect. Experiment 3 showed that the absence of word length and phonemic similarity effects in the younger children was not due to a floor effect, because similar results were obtained in the serial recall of lists of fixed length. In all three experiments the processing demands of the suppression task were controlled for by comparing it with a simple motor task involving tapping. In the younger children, suppression and tapping had the same effect; in the older children, tapping reduced performance but did not abolish...

Developing the theory of working memory.

The theory of working memory was devised to explain the effects of a concurrent memory load in various experimental situations in terms of the operation of a central executive processor and a phonemic response buffer. It also explains the effects of phonemic similarity, articulatory suppression, word length, and unattended speech. Experiment 1 demonstrated that a concurrent memory load markedly reduced the phonemic similarity effect in immediate serial recall, which was taken to support the concept of a limited-capacity phonemic response buffer. A more detailed analysis of the results suggested that a concurrent memory load may affect the storage capacity of the central executive processor and the translation of orthographic stimuli into phonological representations, as well as the storage capacity of the phonemic response buffer. Experiment 2 showed that a concurrent free-recall task reduced the phonemic similarity effect in immediate serial recall, but only in the case of visually presented sequences of items. Moreover, unattended speech was found to have no effect upon performance in immediate free recall. These results were taken to imply that the phonemic response buffer contributes only to performance in cognitive tasks that require the accurate retention of serial-order information.

Does articulatory suppression eliminate the phonemic similarity effect in short-term recall?

Concurrent articulatory suppression does not appear to attenuate the effect of phonemic similarity upon short-term recall under conditions of auditory presentation. On theoretical grounds, the effect should be entirely abolished with visual presentation, but the available evidence is equivocal. The present study investigated the immediate serial recall of visually presented sequences of letters and words. Articulatory suppression reduced the overall performance and eliminated the phonemic similarity effect.

The effect of articulatory suppression in free recall

When subjects are required to utter a series of redundant speech sounds while memorizing lists of words, performance is impaired and the effect of phonemic similarity is reduced. If the recency effect in free recall is based upon phonemic coding then it should be very susceptible to the effects of such a procedure. Two experiments therefore explored the influence of articulatory suppression on performance in free recall. Both produced reliable effects of suppression, but neither showed the predicted interaction between suppression and serial position. It is suggested that the recency effect does not reflect a short-term phonemic store.

Retroactive effect of phonemic similarity on short-term recall of visual and auditory stimuli.

Retroactive effect of phonemic similarity on short-term recall of visual and auditory stimuli.