Mechanisms of aural encoding: VI. Consonants and vowels are remembered as subsets of distinctive features

An attempt was made to examine the manner in which consonants and vowels are coded in short-term memory. under identical recall conditions. Ss were presented with sequences of consonant-vowel digrams for serial recall. Sequences were composed of randomly presented consonants paired with/a/ or randomly presented vowels paired with /d/. Halle’s distinctive feature system was used to generate predictions concerning the frequency of intrusion errors. among phonemes. These predictions were based on the assumption that phonemes are discriminated in memory in terms of their component distinctive features, so that intrusions should most frequently occur between phonemes sharing similar distinctive features. The analysis of intrusion errors revealed that each consonant and vowel phoneme was coded m short-term memory by a particular combination of distinctive features which differed from one phoneme to another. A given phoneme was coded by the same set of distinctive features regardless of the number of syllables in the sequence. However, distinctive feature theories were not able to predict the frequency of intrusion errors for phonemes presented in the middle serial positions of a sequence with 100% accuracy. The results of the experiment support the notion that consonant and vowel phonemes are coded in a similar manner in STM and that this coding involves the retention of a specific set of distinctive features for each phoneme.     

The relation between discriminability and memory for vowels,consonants, and silent-center vowels

People remember lists of vowel-contrasting syllables better than lists that vary only in stop consonant identity. Most views suggest that this difference is due to the structure of immediate memory and the greater discriminability of vowels compared with consonants. In all of these views, there is a presumed systematic relationship between discriminability and recall so that the more discriminable an item, the better that item should be recalled. The 11 experiments reported here measured the relative discriminability of and compared serial recall for (1) intact syllables that varied only in the medial vowel, (2) intact syllables that varied only in the initial consonant, and (3) syllables with the center vowel replaced by silence (so-called silent-center vowels). When item discriminability, as measured by identification, was equated for consonant-contrasting and silent-center lists, serial recall performance was also equal. However, even when the vowels were less discriminable than the consonants or silentcenter vowels, serial recall performance for the vowels was still better. These results are problematic for theories based on acoustic discriminability but can be explained parsimoniously by Nairne’s (1990) feature model.     

Different memory functions for consonants and vowels

Different memory functions were obtained for consonants (C) and vowels (V) in a serial recall task. In general, the most recently heard vowels in a sequence were easier to recall than the most recently heard consonants. This effect was observed for auditorily presented sequences of CV or VC syllables, but was not observed for visually presented stimuli. The results were explained in terms of a limited capacity acoustic storage in which vowels are preserved longer than consonants. Retrieval of the last vowels from this storage was presumed to cause the vowel recency effect.     

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.     

Forgetting and redintegration of consonants and vowels in pseudoword lists

Immediate recall of phonemes was studied in a pseudoword span task. Finnish participants recalled lists of increasing length, consisting of C(consonant)V(vowel)CVCV pseudowords. The lists were made up from pools of 12 pseudowords. There were three types of lists. In the non‐redundant lists the items were unpredictable combinations of consonants and vowels. In consonant‐redundant lists, all items had the consonant frame /t/_/s/_/l/. In vowel‐redundant lists, all items had the vowel frame _/u/_/e/_/o/. Unlike redundant last syllables in a previous experiment, neither consonant nor vowel redundancy helped list recall. Instead, a harmful phonological similarity effect was apparent in the vowel‐redundant case but not the consonant‐redundant case. A phoneme‐level analysis of recall showed that consonants were recalled better in consonant‐redundant lists and vowels were recalled better in vowel‐redundant lists compared to non‐redundant lists. Vowels appeared to be more important for discrimination between items, with redundancy resulting in confusions. The consequences of phoneme‐level forgetting and redintegration for item‐ and list‐level recall are discussed.     

Mechanisms of aural encoding: VIII. Phonetic interference and context-sensitive coding in short-term memory

In previous experiments Ss were presented for ordered recall with sequences of five consonant phonemes paired with /a/ in which the middle three consonant phonemes shared the same manner of articulation (voiced, unvoiced, nasal), the same place of articulation (front, middle, back), or neither the same manner nor place of articulation (control sequences). Compared to performance in control sequences, the middle consonant phoneme was always more difficult to recall in manner of articulation sequences but not in place of articulation sequences. The results suggested that for these sequences consonant phonemes were not remembered in terms of their place of articulation. In the present experiment, sequences of consonant-vowel (CV) or vowel-consonant (VC) syllables were presented for recall in which each consonant phoneme was paired with a different vowel. When consonant phonemes in the different sequence types were presented for recall with different vowels, phonetic interference was observed for the middle consonant in place of articulation sequences as well as manner of articulation sequences, and the effect was observed in both CV and VC groups. It was suggested that vowels are encoded in short-term memory in terms of their place of articulation and that presenting consonant phonemes for recall with different vowels caused Ss to use this dimension to code consonant phonemes in short-term memory.     

前分类声音存储器对声调和情绪韵律的加工

采用系列位置回忆任务, 探讨作为声调语言的汉语普通话中声调及情绪信息是否具有近因及后缀效应, 从而揭示同为超音段信息的声调和情绪韵律在前分类声音存储器(Precategorical Acoustic Storage, PAS)中是否具有单独的表征, 及该表征可能受到哪些因素的影响。实验一和二分别考察了声调是否具有近因和后缀效应, 实验三和四分别考察了情绪信息是否具有近因和后缀效应。实验结果发现两者均在PAS存储器中有单独的表征, 但这种表征会受到一些因素的影响, 且受影响的方式不一样。研究结果表明作为超音段信息的声调和情绪信息在表征上的不稳定性和脆弱性, 及在短时记忆加工过程中的特殊性。     

Recency and the modality effect in immediate ordered recall

In immediate ordered recall, recency is the improved recall of the last item of a presentation, and the modality effect is the advantage for an acoustic presentation over a subvocalized visual presentation, primarily occurring at the last serial position. Experiment 1 tested grouped presentations. There was a modality effect for the first item of the last group, even though that item was at the third-to-last or fourth-to-last serial position. In Experiment 2, for vocalized presentations of syllables ending in a, recency was larger for staccato speech than legato speech; for subvocalized presentations, there was a substantial recency for the legato style. In Experiment 3, recency was larger for a set of syllables ending in ATE than for a set of syllables ending in AME. These results suggest that recency cannot be explained by the existence of a fixed-capacity store, auxiliary to the auditory short-term store, that retains only some types of presentations. It is suggested instead that recency might reflect an auxiliary method of using the information in the auditory short-term store.     

Acoustic memory and the perception of speech

The nature of acoustic memory and its relationship to the categorizing process in speech perception is investigated in three experiments on the serial recall of lists of syllables. The first study confirms previous reports that sequences comprising the syllables, bah, dah, and gah show neither enhanced retention when presented auditorily rather than visually, nor a recency effect—both occurred with sequences in which vowel sounds differed (bee, bih, boo). This was found not to be a simple vowel-consonant difference since acoustic memory effects did occur with consonant sequences that were acoustically more discriminable (sha, ma, ga and ash, am, ag). Further experiments used the stimulus suffix effect to provide evidence of acoustic memory, and showed (1), increasing the acoustic similarity of the set grossly impairs acoustic memory effects for vowels as well as consonants, and (2) such memory effects are no greater for steady-state vowels than for continuously changing diphthongs. It is concluded that the usefulness of the information that can be retrieved from acoustic memory depends on the acoustic similarity of the items in the list rather than on their phonetic class or whether or not they have “encoded” acoustic cues. These results question whether there is any psychological evidence for “encoded” speech sounds being categorized in ways different from other speech sounds.     

Forgetting and redintegration of consonants and vowels in pseudoword lists

Immediate recall of phonemes was studied in a pseudoword span task. Finnish participants recalled lists of increasing length, consisting of C(consonant)V(vowel)CVCV pseudowords. The lists were made up from pools of 12 pseudowords. There were three types of lists. In the non-redundant lists the items were unpredictable combinations of consonants and vowels. In consonant-redundant lists, all items had the consonant frame /t/_/s/_/l/. In vowel-redundant lists, all items had the vowel frame _/u/_/e/_/o/. Unlike redundant last syllables in a previous experiment, neither consonant nor vowel redundancy helped list recall. Instead, a harmful phonological similarity effect was apparent in the vowel-redundant case but not the consonant-redundant case. A phoneme-level analysis of recall showed that consonants were recalled better in consonant-redundant lists and vowels were recalled better in vowel-redundant lists compared to non-redundant lists. Vowels appeared to be more important for discrimination between items, with redundancy resulting in confusions. The consequences of phoneme-level forgetting and redintegration for item- and list-level recall are discussed.     

Recency and suffix effects in serial recall of musical stimuli

Auditory presentation of verbal items leads to larger recency effects in recall than visual presentation. This enhanced recency can be eliminated if a stimulus suffix (an irrelevant sound) follows the last item. Four experiments tested the hypothesis that recency and suffix effects in serial recall result from a speech-specific process. It was demonstrated that serial recall of musical notes played on a piano exhibited substantial recency effects. These recency effects were reduced when the list items were followed by either a piano chord or the word start. However, a white-noise suffix had no effect on recency. This pattern of data is consistent with current work on auditory perception and places constraints on theories of recency and suffix effects.     

Enumeration produces poor primacy for tactile presentation relative to visual and auditory presentation as the only modality effect

Methodological biases may help explain the modality effect, which is superior recall of auditory recency (end of list) items relative to visual recency items. In 1985 Nairne and McNabb used a counting procedure to reduce methodological biases, and they produced modality-like effects, such that recall of tactile recency items was superior to recall of visual recency items. The present study extended Nairne and McNabb's counting procedure and controlled several variables which may have enhanced recall of tactile end items or disrupted recall of visual end items in their study. Although the results of the present study indicated general serial position effects across tactile, visual, and auditory presentation modalities, the tactile condition showed lower recall for the initial items in the presentation list than the other two conditions. Moreover, recall of the final list item did not differ across the three presentation modalities; modality effects were not found. These results did not replicate the findings of Nairne and McNabb, or much of the past research showing superior recall of auditory recency items. Implications of these findings are discussed.     

Is there a modality effect? Evidence for visual recency and suffix effects

In Experiment 1, four groups of 16 subjects performed ordered recall of six-syllable lists in both suffix and nonsuffix conditions. Sequential presentation of the lists varied for each group. In the auditory presentation, the syllables were delivered from one location only and were read aloud by the subjects. For the visual, spatially nondistributed presentation, the syllables appeared in one location only and were read silently. For visual, spatially distributed presentations, the syllables were spread out either vertically or horizontally and were read silently. Very robust recency and suffix effects were found in the auditory presentation, as well as in visual, spatially distributed presentations. In Experiment 2, 16 subjects performed ordered recall of visually presented lists with the items spread out vertically and conflicting spatial and temporal orders. A reliable recency effect was found for the final block of trials. In Experiment 3, 16 subjects performed ordered recall in the same conditions as in Experiment 2, except that they were instructed to recall the temporal order in which the spatial positions would be filled in. A bow-shaped curve and a strong recency effect were obtained.     

The relationship between memory performance and the number of rehearsals in free recall

The purpose of the present study was to examine the relationship between the number of rehearsals and long-term recall performance by means of an overt rehearsal procedure. Subjects were induced to concentrate their rehearsal activity on specific items in free recall tasks. In Experiment 1, both the primacy and the recency items that had received additional rehearsals were recalled with higher probability than were the ordinarily rehearsed items in immediate recall but not in final recall. Experiment 2 was designed to extend the occasions for subjects’ rehearsal by manipulating the rate of item presentation. The overall pattern of resulting data shewed that for neither recency items nor primacy items does the additional overt rehearsal reliably lead to facilitative effects on long-term recall performance. The possibility of a qualitative change in rehearsal is discussed.     

Recency effects in delayed recall of mouthed stimuli

Auditory presentation leads to greater recency effects in recall than does visual presentation. This phenomenon (the modality effect) is found in both free and serial recall and in both immediate and delayed recall. Silent mouthing of visually presented stimuli also leads to enhanced recency effects in immediate serial recall. Two experiments reported here extend the generality of the mouthing effect by demonstrating that enhanced recency effects of mouthed stimuli occur in delayed serial and free recall. These results are inconsistent with theories that attribute the modality effect to a purely auditory sensory memory.     

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.     

The influence of word frequency on recency effects in directed free recall

Leading theoretical explanations of recency effects are designed to explain the reported absence of a word frequency effect on recall of words from recency serial positions. The present study used a directed free-recall procedure (J. J. Dalezman, 1976) and manipulated the frequency composition of the word lists (pure and mixed). Overall, with pure lists, a greater proportion of high-frequency (HF) words were recalled than low-frequency (LF) words, and with mixed lists, a greater proportion of LF words were recalled than HF words. Of importance, this recall advantage for one frequency over the other as a function of list composition was evident across the last three serial positions, indicating an influence of word frequency on recency effects that is dependent on the frequency composition of the lists. These results challenge one of the major assumptions on which several theories of recency effects have been based.     

Effects of speaker variability and phoneme location on speech perception

The effects of variation in a speaker's voice and temporal phoneme location were assessed through a series of speeded classification experiments. Listeners monitored speech syllables for target consonants or vowels. The results showed that speaker variability and phoneme-location variability had detrimental effects on classification latencies for target sounds. In addition, an interaction between variables showed that the speaker variability effect was obtained only when temporal phoneme location was fixed across trials. A subadditive decrement in latencies produced by the interaction of the two variables was also obtained, suggesting that perceptual loads may not affect perceptual adjustments to a speaker's voice in the same way that memory loads do.     

The separate but related origins of the recency effect and the modality effect in free recall

The recency effect found in free recall can be accounted for almost entirely in terms of the recall of ordered sequences of items. It is such sequences, presented at the end of the stimulus list but recalled at the very beginning of the response protocol, which produce a recency effect. Such sequences are recalled at the beginning of the response protocol equally often following auditory and visual presentation. These same stimulus sequences are also frequently recalled other than initially in the response protocol following auditory presentation. However, such responses are rarely found following visual presentation. The modality effect in free recall, the advantage of auditory over visual presentation, can be substantially accounted for in these terms. Theoretical and procedural implications of these data are discussed.     

Do updating tasks involve updating? Evidence from comparisons with immediate serial recall

Updating tasks require participants to process a sequence of items, varying in length, and afterwards to remember only a fixed number of the elements of the sequence; the assumption being that participants actively update the to-be-recalled list as presentation progresses. However recent evidence has cast doubt on this assumption, and the present study examined the strategies that participants employ in such tasks by comparing the serial position curves found in verbal and visuo-spatial updating tasks with those seen in standard serial recall tasks. These comparisons showed that even when the same number of items are presented or recalled, participants perform less well in an updating than a serial recall context. In addition, while standard serial position effects were observed for serial recall, marked recency and reduced or absent primacy effects were seen in updating conditions. These findings suggest that participants do not typically adopt a strategy of actively updating the memory list in updating tasks, but instead tend to wait passively until the list ends before trying to recall the most recently presented items.