Individual Differences in Short-Term Memory

The relationship between tests of sustained attention and fluid intelligence

The relationship between item identification and short-term memory (STM) was investigated. It was hypothesized that both identification and memory storage make demands upon the individual's total available processing space, and that as the information load increases, recall is more dependent upon efficient identification. In Experiment 1, item-identification speed for 24 stimuli was significantly correlated with short-term recall of each stimulus, r(22) = .57, p < .05. Individual differences in item identification were not significantly related to individual differences in STM in Experiment 1, and were significantly related for only one of three stimulus sets in Experiment 2. When a measure of identification efficiency, independent of overall speed of identification, was computed for the subjects in Experiment 1, identification and STM were significantly related, r(17) = .52, p < .05. It was concluded that item identification is an important source of variance in shortterm memory capacity, and that the larger remaining variance probably was due to individual differences in total processing space.

Computational modeling of individual differences in short term memory search

Four groups of children were tested with a serial short term memory (STM) task. Three of the groups were matched in IQ and age, but differed in reading ability from reading-disabled to reading-superior. The fourth group consisted of competent readers matched in IQ with the other three groups, but two years younger than the other children. The STM data showed that (1) differences between the groups were confined mainly to the recall of recency items; (2) within the three older groups, the superior readers were superior to the competent readers, who in turn were superior to the disabled readers; (3) the younger competent readers were superior to the older disabled readers, in spite of the similarity in their reading test scores. These data are discussed both in terms of their implications for physiological approaches to the STM/reading relationship and for the possible causal nature of the relationship.

Encoding strategy accounts for individual differences in change detection measures of VSTM

Use of phonological coding during reading and short-term memory tasks was examined in 12 participants with congenital speech impairments who had reading grade levels of 3.0 or better. Six of the participants had no intelligible speech (anarthria) and six had moderate to severe speech production impairments (dysarthria). All 12 participants were capable of judging the homophony of printed words and nonwords, indicating that accurate phonological coding of text can occur in the absence of speech. Moreover, five participants with dysarthria and two with anarthria appeared to employ phonological coding in short-term memory tasks, as indicated by a phonological similarity effect in serial order memory, and also more weakly by a word length effect in serial order memory. These data indicate that persons with severe congenital speech impairments can learn to use phonological coding during reading and short-term memory tasks; articulatory coding is therefore not a necessary part of the phonological coding process in either word identification or short-term memory. In this study, four of the participants with anarthria did not engage in phonological coding during short-term memory tasks. These participants had more severe deficits in identifying printed words than other participants. Possible explanations of these individual differences are discussed.

There are age-related differences in the rat's short-term memory processes. Rats 24-25 days old are 90% correct when the delay interval separating the forced run and choice run of a trial is either 10 or 30 s, but they perform at chance when the delay interval is 60 s. In contrast, the choice performance of 30-day-old rats remains constant across all delay intervals. It is reported that the cholinergic agent physostigmine dramatically improved the short-term-memory-based performance of rats 24-25 days old such that they displayed no loss in choice accuracy even when the delay interval was 60 s. No such enhanced performance was seen in rats treated with neostigmine, a peripherally acting anticholinesterase. The results support the hypothesis that postnatal maturational differences in central cholinergic systems may contribute to age-related differences in short-term memory.

Serial order short-term memory capacities and specific language impairment: No evidence for a causal association

The Other Side of the Error Term - Aging and Development as Model Systems in Cognitive Neuroscience

In this study we investigated whether we could distinguish the use of specific verbal and visual short term memory (STM) processes in children, or whether the differences in memory performance could be interpreted only in terms of quantitative differences. First, the number of processes involved in the responses on six STM tasks (serial order reconstruction) of 210 primary school children aged 5–12 years was examined by means of latent states. The number of items to reconstruct was manipulated to unravel quantitative differences in responses (high or low performance), and the similarity of the items was manipulated to distinguish qualitative differences in responses (verbal or visual processing). Furthermore, we examined how children changed from one type of process to another on tasks with list lengths of 3, 5, and 7 items by means of the dynamics between the latent states using a latent Markov model. The results showed that two latent states representing the use of specific verbal and visual STM processes could be distinguished on all the tasks. Moreover, two latent states showing merely differences in performance were also found. These findings underline the value of latent variable models to unravel differences between as well as within individuals in the use of cognitive processes.

In three experiments, we studied the relation between degree of implicit learning and two aspects of short-term memory: (1) the activation level of the to-be-learned information, and (2) individual differences in short-term memory capacity. In all the experiments, we used the Nissen and Bullemer (1987) serial reaction time paradigm or a modification thereof. The effects of activation level were assessed by experimentally manipulating the rate of presentation. Individual differences in short-term memory capacity were assessed via traditional span measures. The experiments demonstrated that the rate of presentation reliably affected an indirect measure of learning (i.e., response time) under both incidental and intentional task instructions and under both single-task and dual-task conditions. Short-term memory span was reliably related to the indirect measure of learning only in some experimental conditions. The findings represent important constraints for models of implicit serial learning and are discussed within a general framework for understanding implicit learning and memory.

Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes.

Complexity as a reflection of the dimensionality of a task

Musicians are often regarded as a positive example of brain plasticity and associated cognitive benefits. This emerges when experienced musicians (e.g., musicians with more than 10 years of music training and practice) are compared with nonmusicians. A frequently observed behavioral finding is a short-term memory advantage of the former over the latter. Although available meta-analysis reported that the effect size of this advantage is medium (Hedges’s g = 0.5), no literature study was adequately powered to estimate reliably an effect of such size. This multilab study has been ideated, realized, and conducted in lab by several groups that have been working on this topic. Our ultimate goal was to provide a community-driven shared and reliable estimate of the musicians’ short-term memory advantage (if any) and set a method and a standard for future studies in neuroscience and psychology comparing musicians and nonmusicians. Thirty-three research units recruited a total of 600 experienced musicians and 600 nonmusicians, a number that is sufficiently large to estimate a small effect size (Hedges’s g = 0.3) with a high statistical power (i.e., 95%). Subsequently, we measured the difference in short-term memory for musical, verbal, and visuospatial stimuli. We also looked at cognitive, personality, and socioeconomic factors that might mediate the difference. Musicians had better short-term memory than nonmusicians for musical, verbal, and visuospatial stimuli with an effect size of, respectively, Hedges’s g s = 1.08 (95% confidence interval [CI] = [0.94, 1.22]; large), 0.16 (95% CI = [0.02 0.30]; very small), and 0.28 (95% CI = [0.15, 0.41]; small). This work sets the basis for sound research practices in studies comparing musicians and nonmusicians and contributes to the ongoing debate on the possible cognitive benefits of musical training.

The quality of education in Indonesia is still relatively low when compared with other countries. To improve student achievement, stimulation can be provided to improve learning abilities and memory abilities. The learning and memory process will be optimal if a person is in an alpha brain wave state (8 to 12 Hz). Music that has a tempo of around 60 beats per minute, such as classical music, has the ability to stimulate alpha brain waves. Dangdut music is more familiar to Indonesian people and there is dangdut music which can change alpha brain waves to be more dominant. This type of research is a pre-experimental design with a crossover design. This research aims to see the differences between dangdut and classical music in improving short-term memory. The sampling technique used was purposive sampling with a sample size of 30 people. Short-term memory measurements were carried out before and after receiving music exposure for 30 minutes. Measurements were carried out using the digit span test method. The result was that there was a significant increase in short-term memory after exposure to dangdut and classical music. The conclusion of this research is that dangdut music and classical music both have an impact on improving short-term memory abilities equally well.