Transient phonemic codes and immunity to proactive interference

Empirical data indicate that when memory for subspan lists of taxonomically related material is tested immediately after study, prior experience with lists involving the same material has no effect upon recall or recognition. In six experiments, we explored the possibility that immunity to proactive interference (PI) is related to discriminative information that is provided by transient phonemic codes. In these experiments, we manipulated the strength of phonemic codes as well as their presence or absence. Immunity to PI was found only when it was presumed that a phonemic representation of the target items existed and that information provided discriminative information. In all other cases, PI was observed. The finding that PI effects correspond with the manipulation of phonemic information in a principled fashion provides strong evidence for the role of phonemic codes in producing short-term PI effects.     

Cuing effects in short-term recall

Past research indicates that short-term memory can be immune to the effects of proactive interference (PI). Past research also indicates that immunity to PI is found only in those circumstances where phonemic representations of to-be-remembered items are present and provide discriminative information. The first three experiments demonstrate the existence of a further boundary condition. PI is observed only if interfering and target items are subsumed by the same cue. This finding suggests that short-term recall, like long-term recall, is cue dependent. Cuing effects are further explored in two experiments that manipulate category dominance. The finding that category dominance effects parallel PI effects strongly suggests that retrieval cues play a critical role in short-term recall.     

Determinants of Short-term Forgetting: Decay,Retroactive Interference,or Proactive Interference?

In two experiments short-term forgetting was investigated in a short-term cued recall task designed to examine proactive interference effects. Mixed modality study lists were tested at varying retention intervals using verbal and nonverbal distractor activities. When an interfering foil was read aloud and a target item read silently, strong PI effects were observed for both types of distractor activity. When the target was read aloud and followed by a verbal distractor activity, weak PI effects emerged. However, when a target item was read aloud and nonverbal distractor activity filled the retention interval, performance was immune to the effects of PI for at least 8 seconds. The results indicate that phonological representations of items read aloud still influence performance after 15 seconds of distractor activity.     

Proactive interference and cuing effects in short-term cued recall: Does foil context matter?

Tehan and Humphreys's (1995, 1996) short-term cued recall paradigm showed that recall in short-term memory is cue driven. In critical trials, the participants studied two blocks of four words each and were required to forget the first block while remembering the second block. A foil in the first block (e.g., orange) was related to a target (e.g., carrot) in the second block. Proactive interference (PI) was evident when a retrieval cue was used that subsumed the foil and the target (e.g., type of juice), but not when a cue was used that subsumed only the target (e.g., type of vegetable). Four experiments were performed to examine the extent to which contextual organization in the foil block would enhance or diminish the foil's efficacy in creating PI. A novel condition was included in which the words in the foil block were studied in a phonologically related context but the target was cued semantically, and vice versa with a semantic context and phonological cue. There were no differences in recall accuracy between conditions with and without contextual organization, but reliable increases in foil intrusions were observed when contextual organization was present. Contextual organization enhanced the foil, rather than diminished it, but the strengthened foil generated PI only when the cue subsumed the foil and the target and had no effect when the cue subsumed only the target. The results are consistent with a cue-driven retrieval interpretation of short-term recall.     

Immunity to proactive interference is not a property of the focus of attention in working memory

The Focus of Attention (FOA) is the latest incarnation of a limited capacity store in which a small number of items, in this case four, are deemed to be readily accessible and do not need to be retrieved. Thus a corollary of these ideas is that those items in the FOA are always immune to proactive interference. While there is empirical support for instances of immunity to PI in short-term retention tasks that involve memory for four-item lists, there are also many instances in which PI is observed with four-item lists as well as instances where PI and immunity to PI can be shown in the same experiment. In contrast to the FOA assumptions, an alternative cue-based account predicts both the presence of PI and immunity to PI as a function of the relation between the cues available and the particular test. Three experiments contrasted the FOA assumptions and the cue-based approach in a short-term cued recall task in which PI is manipulated by testing whether the presentation of previous, similar items would interfere with immediate recall of three list items. The results indicated that even with very short lists, both PI and immunity to PI could be observed. The PI effects observed in our experiment are at odds with the FOA approach and are more readily explained using the cueing account.     

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 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.     

Orthography,phonology, and meaning: Word features that give rise to feelings of familiarity in recognition

In the present study, it is shown that participants can recognize test cues as resembling studied words even when these cues cannot be used to recall the words that they resemble. After studying a list of words, participants were given a cued recall test for which half of the cues resembled studied words on one particular feature dimension and half resembled nonstudied words on that dimension. In addition to trying to use each cue to recall a study list item, participants rated the degree to which the cue resembled a studied word. For those cues whose targets could not be identified, the mean rating was higher when the cues corresponded to studied items than when they corresponded to nonstudied items. Various types of features can give rise to this phenomenon, which was found when orthographic, phonemic, and semantic cued recall tasks were used. In all of these cases of recognition without recall, analysis of receiver operating characteristics revealed a pattern consistent with that of an equal-variance signal detection process.     

False working memories? Semantic distortion in a mere 4 seconds

False memories are well-established, episodic memory phenomena: Semantically related associates are confidently and erroneously remembered as studied items. We report four experiments yielding similar effects in a working memory paradigm. Four semantically related words were retained over a brief interval. Whether or not the interval was filled with a math verification task, semantically related lures were mistakenly recognized as members of the memory set and took longer to reject than did unrelated negative probes. In a short-term recall task, semantic intrusions exceeded other errors (e.g., phonemic). Our results demonstrate false memory effects for a subspan list when a mere 4 sec was given between study and test. Such rapid semantic errors presumably result from associative processing, may be related to familiarity-based proactive interference in working memory, and are consistent with recent models that integrate short- and long-term memory processes.     

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.     

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 course of proactive interference in immediate probed recall

Measurement of RT in positionally probed immediate recall was used to study the effect of interlist proactive interference (PI) on short-term retention in near- and subspan lists. The first experiment showed a pronounced effect of PI in the sense of a constant increase of RT, but only to the first three serial positions. This was confirmed in a second study that further showed that the size of PI was independent of the size of the preceding list. These results argue against a general acid-bath view of PI but are consistent with the hypothesis of degraded access to the first item. The minimal length of a list susceptible to PI was five items which suggests that PI develops as soon as the list grows beyond the span of direct access to all individual items.     

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.     

Semantic Similarity and Immediate Serial Recall: Is There a Detrimental Effect on Order Information?

Four experiments investigated the disruptive effect of semantic similarity on short-term ordered recall. Experiments 1 and 2 contrasted immediate serial recall performance for lists of semantically similar items, drawn from the same semantic category, with performance for lists that contained items from different categories. Experiments 1 and 2 showed the usual similarity advantage for item information recall, but, contrary to expectations, there was no similarity disadvantage for the recall of order information, even when the level of item recall was controlled. Experiments 3 and 4 replicate and extend these findings by using an order reconstruction task or a limited word pool strategy, both of which yield alternate measures of order retention. These findings clearly contradict the widespread belief stating that semantic similarity hinders the short-term recall of order information. Results are discussed in the light of a retrieval-based account where the effects of semantic similarity reflect the processes called upon at recall: It is suggested that long-term knowledge is accessed to support the interpretation of degraded phonological traces.     

Proactive interference and practice effects in visuospatial working memory span task performance

In the current study the influence of proactive interference (PI) and practice on recall from a visuospatial working memory (WM) task was examined. Participants completed a visuospatial WM span task under either high-PI conditions (a traditional span task) or low-PI conditions (a span task with breaks between trials). Trials of each length (i.e., two to five to-be-remembered items) were equally distributed across three blocks in order to examine practice effects. Recall increased across blocks to a greater extent in the low-PI condition than in the high-PI condition, indicating that reducing PI increased recall from WM. Additionally, in the final block the correlation between fluid intelligence and WM recall was stronger for the high-PI condition than the low-PI condition, indicating that practice reduced the strength of the correlation between span task recall and fluid intelligence, but only in the low-PI condition. These results support current theories that propose that one source of variability in recall from WM span task is the build-up of PI, and that PI build-up is an important contributing factor to the relation between visuospatial WM span task recall and higher-level cognition.     

Phonemic-similarity effects in good vs. poor readers

Experiments 1–4 examined immediate serial recall of rhyming and nonrhyming items by normal and poor readers in Grades 2–4. Children with generally low achievement were excluded from the poor-reader groups, so that the achievement deficit of the poor readers was centered in reading. The poor readers did not differ from the normal readers in their susceptibility to phonemic similarity either with letter lists or with word lists. Children low in both achievement and intelligence were included in Experiment 3, and they also showed normal susceptibility to phonemic similarity, except that phonemic-confusion effects were reduced when task-difficulty levels were high. Experiment 5 further demonstrated that the serial-recall task is relatively insensitive to phonemic-similarity effects when difficulty levels are high. Previous results suggesting that poor readers are relatively insensitive to phonemic similarity in such tasks may have been an artifactual consequence of marked differences in overall task difficulty for the groups compared. Implications of variations in sample-selection procedures also are discussed.     

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.     

Phonemic confusability,precategorical acoustic storage,and the suffix effect

Ss attempted ordered recall of acoustically presented strings of seven consonant-vowel syllables. In a control condition, each string was followed by a tone in presentation, while in the experimental (suffix) conditions, a verbal syllable followed the last to-be-remembered item. The independent variable was the phonemic similarity between the verbal suffix and the memory stimuli Although the verbal syllables produced a large suffix effect as compared with the control condition, and although more errors were made overall when similarity was high, the degree to which the verbal suffix items reduced the recency advantage at the end of the series was independent of their phonemic similarity to the stimuli. This independence was taken as support for a distinction between acoustic and articulatory coding.     

Pattern of intrusions in verbal recall: comparison of Alzheimer's disease, Parkinson's disease, and frontal lobe dementia

Although some researchers have suggested that intrusions in word list learning are more frequent in Alzheimer's disease, recent studies have shown that this might not be true. In fact, intrusions are common in many neurological degenerative diseases. The goal of the present study was to examine the types of intrusions made by three groups of patients, namely patients with Parkinson's disease (PD), Alzheimer's disease (AD), and dementia with prominent frontal lobe semiology (FD). Although PD patients learned more words (trials 1 to 5 on the RAVLT) than the two other groups, there was no significant difference in the total number of intrusions. However, significant differences between groups were observed for nonrelated intrusions, the proportion of PD patients (15.4%) being lower than the proportion of AD (45.5%) and FD (45.8%) patients with this type of intrusions. No other type of intrusions (same category, recurring, phonemic) significantly differentiated between the three groups. The proactive interference effect (PI), measured as the difference between first recall of list A and list B recall, was stronger in PD than in the two other groups, reflecting the strong positive correlation between total number of words recalled on the RAVLT and severity of the PI effect. Prior list intrusions (intrusions from list A while recalling list B items) were significantly more pronounced in FD than in the two other groups. Finally, free associations (series of intrusions related to one another but not to the target items) were observed almost exclusively in FD patients. These findings illustrate some qualitative differences between various neurological degenerative diseases. They also stress the marked similarities between AD and FD with regards to verbal learning.     

Proactive interference in immediate serial recall

Two experiments yielded significant inter-list proactive interference (PI) in immediate serial recall of nine-consonants lists. This argues against the assumption that intra-trial rehearsal is sufficiently powerful to prevent PI from occurring. In the first experiment PI proved to be more pronounced in the case of visually than of auditorily presented lists to the extent that the modality effect on the prerecent items could be completely attributed to PI. PI also enlarged the effect of output interference through reversed order recall. These findings were confirmed in the second experiment which also showed that the effect of PI persisted at a slower presentation rate, suggesting that the role of rehearsal in counteracting PI should not be overestimated. Implications of these results for current notions on short-term retention are discussed.