Two separate verbal processing rates contributing to short-term memory span

Previous research indicates that verbal memory span, the number of words people can remember and immediately repeat, is related to the fastest rate at which they can pronounce the words. This relation, in turn, has been attributed to a general or global rate of information processing that differs among individuals and changes with age. However, the experiments described in this article showed that the rates of 2 processes (rapid articulation and the retrieval of words from short-term memory) are related to memory span but not to each other. Memory span depends on a profile of processing rates in the brain, not only a global rate. Moreover, there appears to be only a partial overlap between the rate variables that change with age and those that differ among individuals.     

The effects of word co-occurance on short-term memory: Associative links in long-term memory affect short-term memory performance.

In immediate serial recall tasks, high-frequency words are recalled better than low-frequency words. This has been attributed to high-frequency words' being better represented and providing more effective support to a redintegration process at retrieval (C. Hulme et al., 1997). In studies of free recall, there is evidence that frequency of word co-occurrence, rather than word frequency per se, may explain the recall advantage enjoyed by high-frequency words (J. Deese, 1960). The authors present evidence that preexposing pairs of low-frequency words, so as to create associative links between them, has substantial beneficial effects on immediate serial recall performance. These benefits, which are not attributable to simple familiarization with the words per se, do not occur for high-frequency words. These findings indicate that associative links between items in long-term memory have important effects on short-term memory performance and suggest that the effects of word frequency in short-term memory tasks are related to differences in interitern associations in long-term memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in short-term memory and subsequent long-term memory for actions.

Short-term memory for actions was investigated for young adult and elderly adult Ss with the Brown-Peterson procedure at retention intervals of 0 and 15 sec. The short-term memory trials were followed by the long-term recall of the prior to-be-remembered actions. The 15-sec retention interval was filled either with no activity or with 1 of 3 different interfering activities. Verbal interference had little effect on short-term memory at either age level. Actions performed in the interval either by the Ss or by the experimenter produced significantly lower recall scores at each age level, with the decrement being more pronounced for the elderly than for the young Ss. The long-term memory results indicated that successful short-term recall enhanced later long-term recall, regardless of age level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Competitive short-term and long-term memory processes in spatial habituation.

Exposure to a spatial location leads to habituation of exploration such that, in a novelty preference test, rodents subsequently prefer exploring a novel location to the familiar location. According to Wagner's (1981) theory of memory, short-term and long-term habituation are caused by separate and sometimes opponent processes. In the present study, this dual-process account of memory was tested. Mice received a series of exposure training trials to a location before receiving a novelty preference test. The novelty preference was greater when tested after a short, rather than a long, interval. In contrast, the novelty preference was weaker when exposure training trials were separated by a short, rather than a long interval. Furthermore, it was found that long-term habituation was determined by the independent effects of the amount of exposure training and the number of exposure training trials when factors such as the intertrial interval and the cumulative intertrial interval were controlled. A final experiment demonstrated that a long-term reduction of exploration could be caused by a negative priming effect due to associations formed during exploration. These results provide evidence against a single-process account of habituation and suggest that spatial habituation is determined by both short-term, recency-based memory and long-term, incrementally strengthened memory. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Differential involvement of cortical receptor mechanisms in working, short-term and long-term memory

Rats received, through bilaterally implanted indwelling cannulae, 0.5 microliter infusions of 6-cyano-7-nitroquinoxaline2,3-dione (CNQX) (0.5 microgram), D-2-amino-5-phophono pentanoic acid (AP5) (5.0 micrograms), muscimol (0.5 microgram), scopolamine (2.0 micrograms), SCH23390 (2.5 micrograms), saline or a vehicle into the CA1 region of the hippocampus, or into the antero-lateral prefrontal (PRE), posterior parietal (PP) and entorhinal cortex (EC). The infusions were given 6 min prior to one-trial step-down inhibitory avoidance training in order to measure their effect on working memory (WM), or immediately post-training in order to measure their effect on short-term (STM) and long-term memory (LTM), 1.5 and 24 h later, respectively. WM was inhibited by CNQX or muscimol given into any of the cortical areas, by SCH23390 given into CA1, PRE or PP, and by scopolamine given into PRE or EC. STM was unaffected by any of the treatments given into PRE, and was inhibited by CNQX or muscimol given into CA1, PP and EC and by scopolamine given into PP, and enhanced by SCH given into CA1. LTM was inhibited by CNQX, muscimol, scopolamine or SCH23390 given into PRE, by scopolamine given into PP, by SCH23390 given into the entorhinal cortex, and by AP5, CNQX, muscimol or scopolamine given into CA1. The results indicate a differential involvement of the various neurotransmitter systems in the three types of memory in the various brain areas, and a separation of the mechanisms and of the regions involved in each. In addition, some of the findings suggested links between WM and LTM processing in PRE, between WM and STM processing in EC and PP, and between all three types of memory in CA1.     

Tapping sensitivity to processing in short-term memory.

Examined the interference between finger tapping and searching in short-term memory (STM). 20 Ss (mean age 22.4 yrs) memorized a set of digits and then executed a series of 17 taps separated by 2 sec subjective time intervals. During each interval, a probe was presented for comparison with the items in the memory set. The amount of processing in STM was varied from series to series by manipulating the number of items in the memory set. Results show that mean duration and variability of intertap intervals increased proportionally with memory set size. This effect is explained as interference between STM processing and the timing component of the tapping performance. The authors suggest that tapping sensitivity to memory load indicates that, under some conditions, variations in tapping performance are valid indicators of STM processing requirements of a concurrent primary task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scopolamine injection into the olfactory bulb impairs short-term olfactory memory in rats.

A previous experiment showed that systemic administration of the muscarinic antagonist scopolamine altered delayed matching in an olfactory task in rats. The present experiment tested whether the impairment could result from blockade of the cholinergic transmission in the first relay structure of the olfactory system, the olfactory bulb. 25 rats served as Ss. The drug was infused directly into both olfactory bulbs before test sessions. Results show that the intrabulbar infusion reproduced the effect of the systemic administration. With a 4-sec delay between target odor and choice test, performances of treated rats remained unchanged; however, with a 30-sec delay, rats performed randomly. Results from a complementary electrophysiological experiment in anesthetized rats support the idea that scopolamine injected into the olfactory bulb was unlikely to have reached more central structures. Further evidence for the involvement of pure sensory areas in short-term memory is concluded. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phonotactic influences on short-term memory

The impact of phonotactic probabilities on serial recall was investigated in a series of experiments. In Experiments 1A and 1B, 7 and 8 year olds were tested on their serial recall of monosyllabic words and of nonwords varying in phonotactic frequencies. A recall advantage to words over nonwords remained when stimuli were balanced for phonotactic probability, but nonword recall showed superior accuracy for high over low probability nonwords, as in Experiment 2. The nonword frequency effect appears to reflect the frequency of constituent syllables rather than biphones. Both lexicality and high phonotactic frequency led to increased proportions of full over partial recall of the memory stimuli. These findings indicate that decayed memory traces in phonological short-term memory can be reconstructed using either lexical or phonotactic knowledge.     

Binomial variability in short-term memory.

Experiments in short-term memory usually collect binary data, e.g., an item is either correctly recalled or not. If the probability of recall is constant for Ss and/or items under a given condition, the proportion based on n observations can be transformed to angles by the arcsin transformation and will have variance 1/n. Violations of the assumptions are discussed and different strategies for pooling are assessed by conventional analysis of variance. Illustrative experiments with distractor and probe techniques, paired-associates and serial presentation, and single-trial free recall are briefly presented. The correspondence between observed and expected results seems good; apparently considerable latitude is possible in pooling Ss or items in data analyses of experiments in short-term memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Slope analysis in short-term memory.

Presents procedures for transforming dichotomously scored data from short-term memory experiments into slope measures for evaluation by analysis of variance techniques. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Binding in short-term visual memory.

The integration of complex information in working memory, and its effect on capacity, shape the limits of conscious cognition. The literature conflicts on whether short-term visual memory represents information as integrated objects. A change-detection paradigm using objects defined by color with location or shape was used to investigate binding in short-term visual memory. Results showed that features from the same dimension compete for capacity, whereas features from different dimensions can be stored in parallel. Binding between these features can occur, but focused attention is required to create and maintain the binding over time, and this integrated format is vulnerable to interference. In the proposed model, working memory capacity is limited both by the independent capacity of simple feature stores and by demands on attention networks that integrate this distributed information into complex but unified thought objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organization of visual short-term memory.

The authors examined the organization of visual short-term memory (VSTM). Using a change-detection task, they reported that VSTM stores relational information between individual items. This relational processing is mediated by the organization of items into spatial configurations. The spatial configuration of visual objects is important for VSTM of spatial locations, colors, and shapes. When color VSTM is compared with location VSTM, spatial configuration plays an integral role because configuration is important for color VSTM, whereas color is not important for location VSTM. The authors also examined the role of attention and found that the formation of configuration is modulated by both top-down and bottom-up attentional factors. In summary, the authors proposed that VSTM stores the relational information of individual visual items on the basis of global spatial configuration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationships between working memory and long-term memory

Recent studies have led to the proposal that working memory operates not as a gateway between sensory input and long-term memory but as a workspace. The core of argument is that access to acquired knowledge and prior learning occurs before information becomes available to working memory. This proposition is a way to accommodate Baddeley's multiple component working memory model and the view that considers that working memory is nothing other than temporary activations of representations and procedures in long-term memory. However, this 'workspace' conception of working memory raises the question of the relationships between the central executive system and long-term memory.     

Exploring developmental differences in visual short-term memory and working memory.

Although visuospatial short-term memory tasks have been found to engage more executive resources than do their phonological counterparts, it remains unclear whether this is due to intrinsic differences between the tasks or differences in participants’ experience with them. The authors found 11-year-olds’ performances on both visual short-term and working memory tasks to be more greatly impaired by an executive suppression task (random number generation) than were those of 8-year-olds. Similar findings with adults (e.g., Kane & Engle, 2000) suggest that the imposition of a suppression task may have overloaded the older children’s executive resources, which would otherwise be used for deploying strategies for performing the primary tasks. Conversely, the younger children, who probably never had the capacity or know-how to engage these facilitative strategies in the first place, performed more poorly in the single task condition but were less affected in the dual task condition. These findings suggest that differences in the children’s ability to deploy task-relevant strategy are likely to account for at least part of the executive resource requirements of visual memory tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coarse-to-fine encoding of spatial frequency information into visual short-term memory for faces but impartial decay.

Face perception studies investigated how spatial frequencies (SF) are extracted from retinal display while forming a perceptual representation, or their selective use during task-imposed categorization. Here we focused on the order of encoding low-spatial frequencies (LSF) and high-spatial frequencies (HSF) from perceptual representations into visual short-term memory (VSTM). We also investigated whether different SF-ranges decay from VSTM at different rates during a study-test stimulus-onset asynchrony. An old/new VSTM paradigm was used in which two broadband faces formed the positive set and the probes preserved either low or high SF ranges. Exposure time of 500 ms was sufficient to encode both HSF and LSF in the perceptual representation (experiment 1). Nevertheless, when the positive-set was exposed for 500 ms, LSF-probes were better recognized in VSTM compared with HSF-probes; this effect vanished at 800-ms exposure time (experiment 2). Backward masking the positive set exposed for 800 ms re-established the LSF-probes advantage (experiment 3). The speed of decay up to 10 seconds was similar for LSF- and HSF-probes (experiment 4). These results indicate that LSF are extracted and consolidated into VSTM faster than HSF, supporting a coarse-to-fine order, while the decay from VSTM is not governed by SF. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Emerging attributes in monkey short-term memory.

Conducted 2 experiments to examine the role of recency information and stimulus novelty and familiarity in delayed-matching-to-sample (DMTS) performance. Five female 5–8 yr old macaques (one of which was not included in Exp II) were tested on DMTS problems in which the correct and incorrect choice stimuli were both familiar, both relatively novel, or different in familiarity. Initially, novelty and familiarity exerted their influence as preferences (familiar stimuli were preferred). As more training was given, however, novelty and familiarity began to act as discriminative attributes. For example, Ss came to use the fact that the to-be-remembered stimulus was relatively novel to reject alternative choice stimuli that were more familiar. Theories of animal memory based on a single memory attribute cannot address these results. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trial-to-trial carryover in auditory short-term memory.

Using a short-term recognition memory task, the authors evaluated the carryover across trials of 2 types of auditory information: the characteristics of individual study sounds (item information) and the relationships between the study sounds (study set homogeneity). On each trial, subjects heard 2 successive broadband study sounds and then decided whether a subsequently presented probe sound had been in the study set. On some trials, the similarity of the probe item to stimuli presented on the preceding trial was manipulated. This item information interfered with recognition, and false alarms increased from 0.4% to 4.4%. Moreover, the interference was tuned so that only stimuli that were very similar to each other interfered. On other trials, the relationship among stimuli was manipulated to alter the criterion subjects used in making recognition judgments. The effect of this manipulation was confined to the trial on which the criterion change was generated and did not affect the subsequent trial. These results demonstrate the existence of a sharply tuned carryover of auditory item information but no carryover of the effects of study set homogeneity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modality effects in short-term verbal memory.

Argues that for short-term memory, auditory presentation is consistently superior to visual presentation, with the difference restricted to recently presented items. A review of the literature indicates that recall increases with fast presentation rates when auditory presentation is used in a serial recall task; otherwise, recall decreases as presentation rate increases. Some puzzling findings on dichotic and bisensory split-span memory are shown to be related to aspects of the modality difference, notably the strong sequential associations in auditory memory. (116 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention gating in short-term visual memory.

Investigated attention shift to a stream of numerals, in rapid serial visual presentation, using 3 graduate students with normal or corrected-to-normal vision. Ss detected a target embedded in a stream of letters presented at the left of fixation and, as quickly as possible, shifted their attention to a stream of numerals at the right of fixation. They attempted to report, in order, the 4 earliest occurring numerals after the target. Numerals appeared at rates of 4.6, 6.9, 9.2, and 13.4 sec. Analyses demonstrated that, for all Ss, targets, and numeral rates, the relative position of numerals in the response sequence showed clustering, disorder, and folding. Reported numerals tended to cluster around a stimulus position 400 msec after the target. Numerals were reported in an apparently haphazard order. The actual order of report resulted from a mixture of correctly ordered numerals with numerals ordered in the direction opposite to their order of presentation. Results are quantitatively described by a strength theory of order and are efficiently predicted by a computational attention gating model (AGM). The AGM may be derived from a more general attention model that assumes that (a) after detection of the target, an attention gate opens briefly to allow numerals to enter a visual short-term memory and (b) subsequent order of report depends on both item strength (how wide the gate was open during the numeral's entry) and on order information (item strength times cumulative strength of prior numerals). (78 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parrel processing in visual short-term memory.

Visual short-term memory for the contrast and spatial frequency of sinusoidal gratings was measured in a delayed discrimination task in which the 2 stimuli to be compared were separated in time by 1-10 s interstimulus intervals (ISIs). Delayed discrimination thresholds for spatial frequency and contrast were compared, both when the 2 types of thresholds were measured in separate blocks of trials and when the 2 types of measures were randomly intermixed in an uncertainty paradigm, which required participants to process information about both dimensions on each trial. In both cases, accuracy of memory for spatial frequency was independent of ISI, but memory for contrast decreased as ISI increased. Performance was lower in the uncertainty case, but only by an amount predicted by statistical decision theory for independent sources. The results are consistent with a model assuming a set of parallel special-purpose visual discrimination and short-term memory mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)