Precategorical acoustic storage and postcategorical lexical storage

A variety of experimental findings have indicated that a system of precategorical acoustic storage is responsible for the recency effect obtained in the immediate serial recall of sequences of digits, consonants, or syllables. This study investigated whether such findings could be generalized to the recall of sequences of words. Experiment 1 showed that phonemic similarity among a sequence of words failed to reduce the modality effect or the recency effect. Experiment 2 demonstrated that this finding was not attributable to a failure to control the phonemic properties of the stimulus material. Experiment 3 showed that the stimulus suffix effect obtained with sequences of words was not affected by the acoustic similarity between the list items and the stimulus suffix. Finally, Experiment 4 demonstrated that phonemic similarity among a sequence of words failed to reduce the stimulus suffix effect. These results were explained by extending the original model of short-term memory to incorporate a system of postcategorical lexical storage.     

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.     

The effect of vowel similarity and syllable length on acoustic memory

Darwin and Baddeley (1974) argue that the presence of recency, suffix, and modality effects are not attributable to the acoustic properties of the stimuli but, rather, to the acoustic distance between the items comprising the test series. The present study is designed to determine whether stimulus duration is a significant variable in acoustic memory. Eight different blocks of synthetic stimuli were prepared; one block each of 60 msec similar and dissimilar syllables and 190 msec similar and dissimilar syllables. The other four blocks consisted of these same vocabularies, but each list in the block had an eighth syllable suffix of the same duration as the syllables in the block. Significant recency and suffix effects are seen for dissimilar syllables of both durations. No effects are demonstrated for 60-msec similar syllables, but both of the effects are seen for 190-msec similar syllables. These results indicate that whether or not a speech sound is preserved in precategorical acoustic storage (PAS) depends upon not only the acoustic distance between the stimuli, but also on other characteristics intrinsic to the stimuli, e.g., stimulus duration.     

Selective phonemic and semantic coding in short-term recall

Probed recall of targets from six-word sequences containing either phonemically similar, semantically similar, or control (i.e., unrelated phonemically and semantically) stimuli was compared under two conditions of encoding. For the semantic encoding condition, in which all cues provided category information about targets to be recalled, semantic similarity interference effects and phonemic similarity facilitation effects were demonstrated. In the phonemic encoding condition, in which all targets were cued by words which rhymed with them, only phonemic similarity interference effects were found. These results were taken to provide further evidence contradictory to the coding-based dichotomization of primary and secondary memory, and to reflect the importance of selective coding strategies induced by task requirements as determinants of interference effects in short-term recall.     

Syllable similarity: The effects of differences in vowels, consonants, and order

In five experiments with synthetic and natural speech syllables, a rating task we used to study the effects of differences in vowels, consonants, and segment order on judged syllable similarity. The results of Experiments I-IV support neither a purely phonemic model of speech representation, in which vowel, consonant, and order are represented independently, nor a purely syllabic model, in which the three factors are integrated. Instead, the data indicate that subjects compare representations in which adjacent vowel and consonant are independent of one another but are not independent of their positions in the syllable. Experiment V provided no support for the hypothesis that this position-sensitive coding is due to acoustic differences in formant transitions.     

The use of abstract graphemic information in lexical access

Three experiments investigated the nature of the information required for the lexical access of visual words. A four-field masking procedure was used, in which the presentation of consecutive prime and target letter strings was preceded and followed by presentations of a pattern mask. This procedure prevented subjects from identifying, and thus intentionally using, prime information. Experiment I extablished the existence of a semantic priming effect on target identification, demonstrating the lexical access of primes under these conditions. It also showed a word repetition effect independent of letter case. Experiment II tested whether this repetition effect was due to the activation of graphemic or phonemic information. The graphemic and phonemic similarity of primes and targets was varied. No evidence for phonemic priming was found, although a graphemic priming effect, independent of the physical similarity of the stimuli, was obtained. Finally Experiment III demonstrated that, irrespective of whether the prime was a word or a nonword, graphemic priming was equally effective. In both Experiments II and III, however, the word repetition effect was stronger than the graphemic priming effect. It is argued that facilitation from graphemic priming was due to the prime activating a target representation coded for abstract (non-visual) graphemic features, such as letter identities. The extra facilitation from same identity priming was attributed to semantic as well as graphemic activation. The implications of these results for models of word recognition are discussed.     

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.     

A tactile suffix effect

Evidence for a representational tactile memory was obtained from a tactile analogue of the auditory suffix effect. In two experiments, a short sequence of tactile stimuli applied to the fingers was followed by an acoustic (control) or tactile (suffix) recall signal. The serial position curves for the two conditions were compared. They revealed similar and strong primacy effects, but recall of the last few stimuli was higher in the control condition. This terminal control advantage was attributed to the retention of raw tactile information.     

Metaphonological Abilities of Spanish Illiterate Adults

The metaphonological abilities of illiterate Spanish-speaking people were evaluated. A group of rudimentary readers who have had deficient schooling was taken as control. The subjects were asked to discriminate between pairs of syllables that are minimally different in terms of phonetic features, to evaluate rhyme relations, to judge whether or not a particular phoneme or syllable was present in an utterance, and to delete and reverse phonemes and syllables. The results show that illiterates are quite good at phonetic discrimination. Almost half of them demonstrated an unequivocal ability to appreciate rhyme. However, their performance on the syllable tasks, and especially on the phoneme tasks, was very poor. There was almost no overlap between the scores of illiterates and rudimentary readers in the phonemic tasks. The present study confirms previous indications that phonemic awareness does not develop as a mere consequence of cognitive or linguistic maturation. It extends this claim to languages that, like Spanish, possess only a small set of vowels. On the other hand, the lack of phonemic awareness does not imply any substantial inferiority in phonemic sensitivity, i.e. the ability to discriminate between minimal pairs.     

Phonemic identification in a phoneme monitoring experiment: The variable role of uncertainty about vowel contexts

Subjects monitored for the syllable-initial phonemes /b/ and /s/, as well as for the syllables containing those phonemes, in lists of nonsense syllables. Time to detect /b/ was a function of the amount of uncertainty as to the identity of the vowel following the target consonant; when uncertainty was low, no difference existed between phoneme and syllable monitoring latencies, but when uncertainty was high, syllables were detected faster than phonemes. Time to detect /s/ was independent of uncertainty concerning the accompanying vowel and was always slower than syllable detection. The role of knowledge of contexts in a phoneme-monitoring task as well as the relative availability of phonemic information to the listener in this task are discussed.     

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.     

Multistable syllables as enacted percepts: a source of an asymmetric bias in the verbal transformation effect

Perceptual changes are experienced during rapid and continuous repetition of a speech form, leading to an auditory illusion known as the verbal transformation effect. Although verbal transformations are considered to reflect mainly the perceptual organization and interpretation of speech, the present study was designed to test whether or not speech production constraints may participate in the emergence of verbal representations. With this goal in mind, we examined whether variations in the articulatory cohesion of repeated nonsense words--specifically, temporal relationships between articulatory events--could lead to perceptual asymmetries in verbal transformations. The first experiment displayed variations in timing relations between two consonantal gestures embedded in various nonsense syllables in a repetitive speech production task. In the second experiment, French participants repeatedly uttered these syllables while searching for verbal transformation. Syllable transformation frequencies followed the temporal clustering between consonantal gestures: The more synchronized the gestures, the more stable and attractive the syllable. In the third experiment, which involved a covert repetition mode, the pattern was maintained without external speech movements. However, when a purely perceptual condition was used in a fourth experiment, the previously observed perceptual asymmetries of verbal transformations disappeared. These experiments demonstrate the existence of an asymmetric bias in the verbal transformation effect linked to articulatory control constraints. The persistence of this effect from an overt to a covert repetition procedure provides evidence that articulatory stability constraints originating from the action system may be involved in auditory imagery. The absence of the asymmetric bias during a purely auditory procedure rules out perceptual mechanisms as a possible explanation of the observed asymmetries.     

A comparison of the McGurk effect for spoken and sung syllables

The importance of visual cues in speech perception is illustrated by the McGurk effect, whereby a speaker’s facial movements affect speech perception. The goal of the present study was to evaluate whether the McGurk effect is also observed for sung syllables. Participants heard and saw sung instances of the syllables /ba/ and /ga/ and then judged the syllable they perceived. Audio-visual stimuli were congruent or incongruent (e.g., auditory /ba/ presented with visual /ga/). The stimuli were presented as spoken, sung in an ascending and descending triad (C E G G E C), and sung in an ascending and descending triad that returned to a semitone above the tonic (C E G G E C#). Results revealed no differences in the proportion of fusion responses between spoken and sung conditions confirming that cross-modal phonemic information is integrated similarly in speech and song.     

Perceptual-motor processing of phonetic features in speech

Some reaction time experiments are reported on the relation between the perception and production of phonetic features in speech. Subjects had to produce spoken consonant-vowel syllables rapidly in response to other consonant-vowel stimulus syllables. The stimulus syllables were presented auditorily in one condition and visually in another. Reaction time was measured as a function of the phonetic features shared by the consonants of the stimulus and response syllables. Responses to auditory stimulus syllables were faster when the response syllables started with consonants that had the same voicing feature as those of the stimulus syllables. A shared place-of-articulation feature did not affect the speed of responses to auditory stimulus syllables, even though the place feature was highly salient. For visual stimulus syllables, performance was independent of whether the consonants of the response syllables had the same voicing, same place of articulation, or no shared features. This pattern of results occurred in cases where the syllables contained stop consonants and where they contained fricatives. It held for natural auditory stimuli as well as artificially synthesized ones. The overall data reveal a close relation between the perception and production of voicing features in speech. It does not appear that such a relation exists between perceiving and producing places of articulation. The experiments are relevant to the motor theory of speech perception and to other models of perceptual-motor interactions.     

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.     

Contextual control of stimulus generalization and stimulus equivalence in hierarchical categorization

The purpose of this study was to determine whether hierarchical categorization would result from a combination of contextually controlled conditional discrimination training, stimulus generalization, and stimulus equivalence. First, differential selection responses to a specific stimulus feature were brought under contextual control. This contextual control was hierarchical in that stimuli at the top of the hierarchy all evoked one response, whereas those at the bottom each evoked different responses. The evocative functions of these stimuli generalized in predictable ways along a dimension of physical similarity. Then, these functions were indirectly acquired by a set of nonsense syllables that were related via transitivity relations to the originally trained stimuli. These nonsense syllables effectively served as names for the different stimulus classes within each level of the hierarchy.     

Speech, "inner speech," and the development of short-term memory: effects of picture labeling on recall

Three experiments explored the effect of overt speech on children's use of "inner speech' in short-term memory (STM). Experiments 1 and 2 compared recall of a series of pictured objects when 5- and 11-year-olds either labeled stimuli at presentation or remained silent. Use of inner speech was assessed by manipulating word length of the picture names (Experiment 1) or phonemic similarity (Experiment 2). Word length and phonemic similarity had greater effects in the older children and when pictures were labeled at presentation. These tendencies were such that 5-year-olds were sensitive to word length and phonemic similarity only with labeling. Experiment 3 compared labeling by the child with labeling by the experimenter in 5-year-olds. There were no significant differences with respect to overall performance or effects of word length and phonemic similarity. It is suggested that speaking or listening to speech activates and internal "articulatory loop,' and that such activation is especially important when the child's ability to use inner speech in STM has not fully developed.     

Heart rate, recall, and reaction-time measures of levels of processing

A problem of circularity emerges in any attempt to index depth by retention alone. In the present study, reaction time (RT), and heart-rate response were used to index the three qualitatively distinct levels of physical, phonemic, and semantic processing. An additional objective was to distinguish between the three levels under incidental vs intentional learning conditions. Subjects were 46 male undergraduates who were given 30 trials. A trial consisted of the presentation of an orienting question and an imperative word-stimulus separated by a 6-sec. interval. There were three types of questions in order to induce processing to one of the three target levels. The results indicated that recall as well as heart-rate acceleration distinguished between two (physical vs phonemic and semantic) rather than three levels of processing in the incidental condition. Heart-rate change differentiated between incidental and intentional, the intentional condition showing a smaller change. Semantic and phonemic RTs were faster than physical RT, but there were no differences between semantic and phonemic RTs. Intentional recall was superior to incidental recall. It is suggested that psychophysiological indices can provide independent evidence for 'levels of processing.'     

Listening to speech while retaining music: What happens to the right-ear advantage?

On each trial, subjects were played a dichotic pair of syllables differing in the consonant (/ba/, /da/, /ga/) or in the vowel (/ba/, /b?/, /bi/). The pair of syllables was preceded by a melody, or a sentence, and followed by the same or a different melody, or sentence. Subjects either had to retain the first piece of additional material or were free to ignore it. The different combinations of phonemic contrast, additional material, and instruction concerning the additional material were used in different sessions. In each case, the main task of the subjects was to respond to the presence or the absence of the target /ba/ on the ear previously indicated. There was no effect of context on relative ear accuracy, but the right-ear advantage observed for consonants in response latency when subjects retained a sentence gave way to a small nonsignificant left-ear advantage when subjects retained a melody. Right-ear advantage in response latencies was also observed for vowels in the verbal context, but the contextual effect, although in the same direction as for consonants, was very slight. The implications of contextual effects for a theory of the determinants of the auditory laterality effects are discussed.     

Developmental differences in short-lived auditory memory for various classes of speech sounds

Spoken serial recall by second-grade children of aurally presented lists of digits, synthetic stop consonants, and synthetic vowels showed a significant suffix effect (selective debilitation of recall at the final position under the stimulus suffix condition) only for the lists of digits and not for either consonants or vowels. Making the synthetic syllables more distinctive by simultaneously covarying the consonant and vowel failed to produce a suffix effect under a strict scoring criterion which required both consonant and vowel to be recalled correctly; however, when subjects were given credit for partially correct answers the suffix effect emerged. Adults given the redundant consonant-vowel syllables showed a significant suffix effect with the strict scoring criterion. However, when consonants and vowels varied orthogonally, the adults' performance showed the suffix effect only under the lenient scoring criterion. An argument is made for equivalence of basic memorial processing between children and adults, the difference being in the number of features needed to disambiguate the target items and in the ability to integrate these features to exploit interstimulus redundancy.