Memory Scanning Speed Research Articles

Speed of Information Processing and Verbal Working Memory in Children and Adolescents With Cochlear Implants.

Verbal working memory delays are found in many deaf children with cochlear implants compared with normal-hearing peers, but the factors contributing to these delays are not well understood. This study investigated differences between cochlear implant users and normal-hearing peers in memory scanning speed during a challenging verbal working memory task. To better understand variability in verbal working memory capacity within each sample, associations between memory scanning speed, speech recognition, and language were also investigated. Twenty-five prelingually deaf, early implanted children (age, 8-17 yr) with cochlear implants and 25 normal-hearing peers completed the Wechsler Intelligence Scale for Children, Fifth Edition, Letter-Number Sequencing (LNS) working memory task. Timing measures were made for response latency and average pause duration between letters/numbers recalled during the task. Participants also completed measures of speech recognition, vocabulary, and language comprehension. Children with cochlear implants had longer pause durations than normal-hearing peers during three-span LNS sequences, but the groups did not differ in response latencies or in pause durations during two-span LNS sequences. In the sample of cochlear implant users, poorer speech recognition was correlated with longer pause durations during two-span sequences, whereas poorer vocabulary and weaker language comprehension were correlated with longer response latencies during two-span sequences. Response latencies and pause durations were unrelated to language in the normal-hearing sample. Children with cochlear implants have slower verbal working memory scanning speed than children with normal hearing. More robust phonological-lexical representations of language in memory may facilitate faster memory scanning speed and better working memory in cochlear implant users.

Modality Effects on Lexical Encoding and Memory Representations of Spoken Words.

The present study investigated presentation modality differences in lexical encoding and working memory representations of spoken words of older, hearing-impaired adults. Two experiments were undertaken: a memory-scanning experiment and a stimulus gating experiment. The primary objective of experiment 1 was to determine whether memory encoding and retrieval and scanning speeds are different for easily identifiable words presented in auditory-visual (AV), auditory-only (AO), and visual-only (VO) modalities. The primary objective of experiment 2 was to determine if memory encoding and retrieval speed differences observed in experiment 1 could be attributed to the early availability of AV speech information compared with AO or VO conditions. Twenty-six adults over age 60 years with bilateral mild to moderate sensorineural hearing loss participated in experiment 1, and 24 adults who took part in experiment 1 participated in experiment 2. An item recognition reaction-time paradigm (memory-scanning) was used in experiment 1 to measure (1) lexical encoding speed, that is, the speed at which an easily identifiable word was recognized and placed into working memory, and (2) retrieval speed, that is, the speed at which words were retrieved from memory and compared with similarly encoded words (memory scanning) presented in AV, AO, and VO modalities. Experiment 2 used a time-gated word identification task to test whether the time course of stimulus information available to participants predicted the modality-related memory encoding and retrieval speed results from experiment 1. The results of experiment 1 revealed significant differences among the modalities with respect to both memory encoding and retrieval speed, with AV fastest and VO slowest. These differences motivated an examination of the time course of stimulus information available as a function of modality. Results from experiment 2 indicated the encoding and retrieval speed advantages for AV and AO words compared with VO words were mostly driven by the time course of stimulus information. The AV advantage seen in encoding and retrieval speeds is likely due to a combination of robust stimulus information available to the listener earlier in time and lower attentional demands compared with AO or VO encoding and retrieval. Significant modality differences in lexical encoding and memory retrieval speeds were observed across modalities. The memory scanning speed advantage observed for AV compared with AO or VO modalities was strongly related to the time course of stimulus information. In contrast, lexical encoding and retrieval speeds for VO words could not be explained by the time-course of stimulus information alone. Working memory processes for the VO modality may be impacted by greater attentional demands and less information availability compared with the AV and AO modalities. Overall, these results support the hypothesis that the presentation modality for speech inputs (AV, AO, or VO) affects how older adult listeners with hearing loss encode, remember, and retrieve what they hear.

High intensity intermittent games-based activity and adolescents\u2019 cognition: moderating effect of physical fitness

BackgroundAn acute bout of exercise elicits a beneficial effect on subsequent cognitive function in adolescents. The effect of games-based activity, an ecologically valid and attractive exercise model for young people, remains unknown; as does the moderating effect of fitness on the acute exercise-cognition relationship. Therefore, the aim of the present study was to examine the effect of games-based activity on subsequent cognition in adolescents, and the moderating effect of fitness on this relationship.MethodsFollowing ethical approval, 39 adolescents (12.3 ± 0.7 year) completed an exercise and resting trial in a counterbalanced, randomised crossover design. During familiarisation, participants completed a multi-stage fitness test to predict VO2 peak. The exercise trial consisted of 60-min games-based activity (basketball), during which heart rate was 158 ± 11 beats∙min− 1. A battery of cognitive function tests (Stroop test, Sternberg paradigm, trail making and d2 tests) were completed 30-min before, immediately following and 45-min following the basketball.ResultsResponse times on the complex level of the Stroop test were enhanced both immediately (p = 0.021) and 45-min (p = 0.035) post-exercise, and response times on the five item level of the Sternberg paradigm were enhanced immediately post-exercise (p = 0.023). There were no effects on the time taken to complete the trail making test or any outcome of the d2 test. In particular, response times were enhanced in the fitter adolescents 45-min post-exercise on both levels of the Stroop test (simple, p = 0.005; complex, p = 0.040) and on the three item level of the Sternberg paradigm immediately (p = 0.017) and 45-min (p = 0.008) post-exercise.ConclusionsGames-based activity enhanced executive function and working memory scanning speed in adolescents, an effect particularly evident in fitter adolescents, whilst the high intensity intermittent nature of games-based activity may be too demanding for less fit children.

A randomised-controlled trial of the effects of very low-carbohydrate and high-carbohydrate diets on cognitive performance in patients with type 2 diabetes.

This study compared the longer-term effects of a very low-carbohydrate, high-fat diet with a high-carbohydrate, low-fat diet on cognitive performance in individuals with type 2 diabetes (T2D). In total, 115 obese adults with T2D (sixty-six males, BMI: 34·6 (sd 4·3) kg/m2, age: 58 (sd 7) years, HbA1c: 7·3 (sd 1·1) %, diabetes duration: 8 (sd 6) years) were randomised to consume either an energy-restricted, very low-carbohydrate, low-saturated-fat (LC) diet or an energy-matched high unrefined carbohydrate, low-fat (HC) diet with supervised aerobic/resistance exercise (60 min, 3 d/week) for 52 weeks. Body weight, HbA1c and cognitive performance assessing perceptual speed, reasoning speed, reasoning ability, working memory, verbal fluency, processing speed, short-term memory, inhibition and memory scanning speed were assessed before and after intervention. No differences in the changes in cognitive test performance scores between the diet groups were observed for any of the cognitive function outcomes assessed (P≥0·24 time×diet). Percentage reduction in body weight correlated with improvements with perceptual speed performance. In obese adults with T2D, both LC and HC weight-loss diets combined with exercise training had similar effects on cognitive performance. This suggests that an LC diet integrated within a lifestyle modification programme can be used as a strategy for weight and diabetes management without the concern of negatively affecting cognitive function.

The older people, omega-3, and cognitive health (EPOCH) trial design and methodology: A randomised, double-blind, controlled trial investigating the effect of long-chain omega-3 fatty acids on cognitive ageing and wellbeing in cognitively healthy older adults

BackgroundSome studies have suggested an association between omega-3 long-chain polyunsaturated fatty acids (n-3 LC PUFAs) and better cognitive outcomes in older adults. To date, only two randomised, controlled trials have assessed the effect of n-3 LC PUFA supplementation on cognitive function in older cognitively healthy populations. Of these trials only one found a benefit, in the subgroup carrying the ApoE-ε4 allele. The benefits of n-3 LC PUFA supplementation on cognitive function in older normal populations thus still remain unclear. The main objective of the current study was to provide a comprehensive assessment of the potential of n-3 LC PUFAs to slow cognitive decline in normal elderly people, and included ApoE-ε4 allele carriage as a potential moderating factor. The detailed methodology of the trial is reported herein.MethodsThe study was a parallel, 18-month, randomised, double-blind, placebo-controlled intervention with assessment at baseline and repeated 6-monthly. Participants (N = 391, 53.7% female) aged 65-90 years, English-speaking and with normal cognitive function, were recruited from metropolitan Adelaide, South Australia. Participants in the intervention arm received capsules containing fish-oil at a daily dosage of 1720 mg of docosahexaenoic acid and 600 mg of eicosapentaenoic acid while the placebo arm received the equivalent amount of olive oil in their capsules. The primary outcome is rate of change in cognitive performance, as measured by latent variables for the cognitive constructs (encompassing Reasoning, Working Memory, Short-term Memory, Retrieval Fluency, Inhibition, Simple and Choice-Reaction Time, Perceptual Speed, Odd-man-out Reaction Time, Speed of Memory Scanning, and Psychomotor Speed) and assessed by latent growth curve modeling. Secondary outcomes are change in the Mini-mental State Examination, functional capacity and well-being (including health status, depression, mood, and self-report cognitive functioning), blood pressure, and biomarkers of n-3 LC PUFA status, glucose, lipid metabolism, inflammation, oxidative stress, and DNA damage.Trial registrationAustralia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12607000278437

The Prefrontal Model Revisited: Double Dissociations Between Young Sleep Deprived and Elderly Subjects on Cognitive Components of Performance

The prefrontal model suggests that total sleep deprivation (TSD) and healthy aging produce parallel cognitive deficits. Here we decompose global performance on two common tasks into component measures of specific cognitive processes to pinpoint the source of impairments in elderly and young TSD participants relative to young controls and to each other. The delayed letter recognition task (DLR) was performed in 3 studies. The psychomotor vigilance task (PVT) was performed in 1 of the DLR studies and 2 additional studies. For DLR, young TSD (n=20, age=24.60 ± 0.62 years) and young control (n=17, age=24.00 ± 2.42); elderly (n=26, age=69.92 ± 1.06). For the PVT, young TSD (n=18, age=26.65 ± 4.57) and young control (n=16, age=25.19 ± 2.90); elderly (n=21, age=71.1 ± 4.92). Both elderly and young TSD subjects displayed impaired reaction time (RT), our measure of global performance, on both tasks relative to young controls. After decomposing global performance on the DLR, however, a double dissociation was observed as working memory scanning speed was impaired only in elderly subjects while other components of performance were impaired only by TSD. Similarly, for the PVT a second double dissociation was observed as vigilance impairments were present only in TSD while short-term response preparation effects were altered only in the elderly. The similarity between TSD and the elderly in impaired performance was evident only when examining global RT. In contrast, when specific cognitive components were examined double dissociations were observed between TSD and elderly subjects. This demonstrates the heterogeneity in those cognitive processes impaired in TSD versus the elderly.

Histamine H1 receptor antagonist cetirizine impairs working memory processing speed, but not episodic memory

The histaminergic neurotransmitter system is currently under investigation as a target for drug treatment of cognitive deficits in clinical disorders. The therapeutic potential of new drugs may initially be screened using a model of histaminergic dysfunction, for example, as associated with the use of centrally active antihistamines. Of the selective second generation antihistamines, cetirizine has been found to have central nervous system effects. The aim of the present study was to determine whether cetirizine can be used as a tool to model cognitive deficits associated with histaminergic hypofunction. The study was conducted according to a three-way, double-blind, cross-over design. Treatments were single oral doses of cetirizine 10 and 20 mg and placebo. Effects on cognition were assessed using tests of word learning, memory scanning, vigilance, divided attention, tracking and visual information processing speed. Cetirizine 10 mg impaired tracking performance and both doses impaired memory scanning speed. None of the other measures indicated impaired performance. Cetirizine affects information processing speed, but these effects were not sufficient to serve as a model for cognitive deficits in clinical disorders.

Examining the Link between Information Processing Speed and Executive Functioning in Multiple Sclerosis

Slowed information processing speed (IPS) is frequently reported in those with multiple sclerosis (MS), and at least 20% are compromised on some aspect of executive functioning also. However, any relationship between these two processes has not been examined. The Sternberg Memory Scanning Test, Processing Speed Index (WAIS-III), Delis Kaplan Executive Function System (D.KEFS), and Working Memory Index (WMS-III) were administered to 90 participants with MS. Their performance on the PSI was significantly below the normative scores but no deficits in memory scanning speed were evident. The initial response speed of the Sternberg and the PSI were more closely related to D.KEFS performance, particularly in timed tasks with a high cognitive demand (switching tasks). In contrast, memory scanning speed was related to working memory. This study reinforces the link between IPS and working memory in MS, and supports the suggestion that IPS is not a unitary construct.

Assessment of information processing in working memory in applied settings: the paper & pencil memory scanning test

Sternberg's Memory Scanning Test (MST) is a useful paradigm for evaluating the speed and efficiency of information processing in working memory. Unfortunately, the classical MST has major drawbacks for use in applied settings such as the clinic. For example, its administration time is long and the test is too difficult for older people or people with cognitive disorders. It would be advantageous to have a test for the assessment of information processing in working memory for use in applied settings, for example in differential diagnostics in clinical settings. The MST was modified into a format that makes it more appropriate for use in the clinic, the Paper & Pencil MST (P&P MST). The influence of age and age-extrinsic factors on the P&P MST was evaluated in a large sample (n=1839) of healthy and cognitively intact adults (24-81 years) to establish the normal range of performance. Age and education affected all components of information processing in working memory. Gender did not affect the non-memory processing stages in the P&P MST, but affected the speed of memory scanning. An Age x Gender interaction was observed, which suggested that females who were aged below 55 scanned working memory faster than males, and vice versa for people aged above 55. The established P&P MST norms provide a useful tool in applied settings when a person's memory scanning and non-memory processes in working memory are to be evaluated.

Correlation of cognition and FDG-PET findings in early multiple sclerosis

Introduction: Patients with multiple sclerosis (MS), disease history of 11.5 years, an expanded disability status scale (EDSS) up to 6.0 and an involvement of verbal and/or spatial and long-term memory showed a bilateral reduction of glucose metabolism in the cingulate gyrus, thalamus, associative occipital cortex and cerebellum. To our knowledge no similar studies in early stages of MS are reported. Therefore we stressed the question of possible correlation of quality of life, objective cognitive impairment and FDG-PET findings in newly diagnosed definite MS according to McDonald criteria. Methods: In 11 patients (f=4, m=7, mean age: 35 years (CI 25–42), IQ 112 (CI 97–118)) with newly diagnosed definite MS and minor disability (mean EDSS=1.0) neuropsychological testing (VLMT, d2, Benton, TMT) and quality of life measurement (MSQOL-54) were done and correlated with age and education matched healthy group (mean age 33 years (CI 25–38), IQ 112 (100–124)). Additionally all patients were investigated by a FDG-PET. Results: Cognitive impairment reported by patients (MSQOL-54) was correlated with impairment of alertness, processing speed and concentration measured by neuropsychological testing (p<0.05). The FDG-PET analysis showed an increased metabolism of glucose at Brodmann-area 7, 18, 19, 21, and a decrease of glucose metabolism at the thalamus and cerebellum in these patients compared to a age-related healthy group. Discussion: In patients with newly diagnosed MS a increased glucose metabolism in cortical areas associated with secondary visual alertness processing could be demonstrate in contrast to prior findings in long-term MS. We suppose unconscious reactions of the MS patients lead to hyperactivity within the visual cortical regions to equalize the impairment of verbal memory and alertness. In correlation to patients with long-term history of MS reduction of glucose metabolism was found at the thalamus und cerebellum. According to previous studies the significant relationship between reduction of glucose metabolism at the cerebellum and memory scanning speed suggests that functional damage in the posterior fossa may contribute to slowed cognitive processing.

Correlation of cognition and FDG-PET findings in early multiple sclerosis

Introduction: Patients with multiple sclerosis (MS), disease history of 11.5 years, an expanded disability status scale (EDSS) up to 6.0 and an involvement of verbal and/or spatial and long-term memory showed a bilateral reduction of glucose metabolism in the cingulate gyrus, thalamus, associative occipital cortex and cerebellum. To our knowledge no similar studies in early stages of MS are reported. Therefore we stressed the question of possible correlation of quality of life, objective cognitive impairment and FDG-PET findings in newly diagnosed definite MS according to McDonald criteria. Methods: In 11 patients (f=4, m=7, mean age: 35 years (CI 25–42), IQ 112 (CI 97–118)) with newly diagnosed definite MS and minor disability (mean EDSS=1.0) neuropsychological testing (VLMT, d2, Benton, TMT) and quality of life measurement (MSQOL-54) were done and correlated with age and education matched healthy group (mean age 33 years (CI 25–38), IQ 112 (100–124)). Additionally all patients were investigated by a FDG-PET. Results: Cognitive impairment reported by patients (MSQOL-54) was correlated with impairment of alertness, processing speed and concentration measured by neuropsychological testing (p<0.05). The FDG-PET analysis showed an increased metabolism of glucose at Brodmann-area 7, 18, 19, 21, and a decrease of glucose metabolism at the thalamus and cerebellum in these patients compared to a age-related healthy group. Discussion: In patients with newly diagnosed MS a increased glucose metabolism in cortical areas associated with secondary visual alertness processing could be demonstrate in contrast to prior findings in long-term MS. We suppose unconscious reactions of the MS patients lead to hyperactivity within the visual cortical regions to equalize the impairment of verbal memory and alertness. In correlation to patients with long-term history of MS reduction of glucose metabolism was found at the thalamus und cerebellum. According to previous studies the significant relationship between reduction of glucose metabolism at the cerebellum and memory scanning speed suggests that functional damage in the posterior fossa may contribute to slowed cognitive processing.

The contribution of sleep to improvements in working memory scanning speed: A study of prolonged sleep restriction

Working memory scanning and motor response speeds were assessed in chronically sleep restricted participants using the Sternberg item recognition paradigm (SIRP). Twenty-two healthy volunteers (ages 21–30) living in a controlled hospital environment were allowed either 4 h of sleep opportunity (50% of habitual sleep) or 8 h of sleep opportunity (100% of habitual sleep) for 12 days. Working memory scanning efficiency (time taken to access an item in working memory) was tested for the first 9 days of sleep restriction and improved over time in participants permitted an 8 h sleep period, but did not change significantly in participants permitted a 4 h sleep period. Speed of motor response (reaction time independent of cognitive processing) did not change significantly in either group. These results indicate that the efficiency of working memory scanning can improve with repeated practice given sufficient sleep, and that prolonged sleep restriction to 50% of habitual sleep prevents this improvement.

ASSESSMENT OF COGNITIVE FUNCTION OF THE ELDERLY POPULATION: EFFECTS OF DARIFENACIN

Overactive bladder is common in the elderly population, which is susceptible to cognitive disorders and drug induced cognitive impairment. Existing overactive bladder treatments may cause adverse events, such as cognitive impairment, due to antagonism of the M1 receptor in the central nervous system. In this study we evaluated the effect of darifenacin, an M3 selective antagonist, on cognitive function in elderly volunteers without clinical dementia. This double-blind, 3-period crossover study randomized 129 volunteers 65 years or older with no/mild cognitive impairment to receive 3 of 5 treatments, namely darifenacin controlled release (3.75, 7.5 or 15 mg once daily), darifenacin immediate-release (5 mg 3 times daily) or matching placebo for 14 days. Each treatment period was separated by 7 days of washout. Cognitive function tests were completed at baseline and at treatment end. For the primary end points of memory scanning sensitivity, speed of choice reaction time and word recognition sensitivity, there were no statistically significant differences for darifenacin vs placebo. There were no statistically significant differences in secondary variables except memory scanning speed, which increased in all groups relative to baseline, but improvement was greater with placebo than with 3.75 mg darifenacin. Darifenacin treatment was not associated with changes in alertness, contentment or calmness, which are likely to be clinically relevant. Darifenacin was well tolerated. : In elderly volunteers 2 weeks of treatment with darifenacin had no effect on cognitive function compared with baseline and it was not significantly different from placebo. This may be related to its M3 receptor selectivity with negligible M1 receptor antagonism.

Effects of smoking/nicotine on performance and event-related potentials during a short-term memory scanning task.

Nicotine absorbed from cigarette smoke shortens reaction time (RT) in a wide variety of cognitive tasks. However, relatively few studies have tried to isolate the specific stage(s) of information processing affected by smoking/nicotine. The present study was designed to investigate the effect of smoking/nicotine on the short-term memory (STM) scanning stage of information processing in minimally abstaining smokers. Both RT and event-related potentials (ERPs) were measured. A Sternberg-type STM-scanning task was performed before and after smoking each of two cigarettes. One cigarette had a 0.05-mg nicotine yield ("denicotinized") and the other had a 1.1-mg yield ("nicotine-yielding"). On each trial, either 2, 3, or 4 consonants were displayed as a memory set. After a brief interval, a single probe consonant was displayed. If the probe was in the memory set (positive probe) a right button press was required, and if the probe was not in the memory set (negative probe) the left button was pressed. Smoking the nicotine-yielding cigarette but not the denicotinized cigarette shortened RT. However, memory-scanning speed, as estimated from the increase in RT as a function of increasing set size, was not differentially affected by the two types of cigarettes. For the ERPs, smoking the nicotine-yielding but not the denicotinized cigarette (a) reduced N200 latency to both the memory-set stimuli and negative probes, (b) increased N200 amplitude to negative probes and P300 amplitude to both types of probes, and (c) produced a sustained negative shift in memory-set ERP amplitude beginning around 600 ms post-stimulus. While smoking/nicotine shortened probe RT, it did not affect the speed of STM scanning. Moreover, the ERP-latency effects obtained for the probes were small relative to the effects of smoking/nicotine on RT, suggesting that smoking/nicotine shortens RT primarily by affecting response-related processes.

The relationship between articulation time and memory performance in verbal and visuospatial tasks.

The number of verbal items which can be recalled immediately is related to the rate at which an individual can speak. Subvocal rehearsal, or articulatory recoding in working memory, has been assumed to mediate this relation. For spatial items recalled in order there is also a relationship with articulation rate, which is not related to verbal rehearsal of the items. One reason for this might be that the relationship is mediated by speed of memory scanning for serial position tags in a memory set, which is related to processing speed. Subjects were asked to perform visuospatial memory tasks which involved serial position and visuospatial memory tasks in which serial position was not involved. They also performed a digit span task. The results indicated that the visuospatial memory tasks were highly related, that they were only weakly related to digit span, and that articulation rate was correlated with every measure of memory performance used, whether serial position was involved or not. There is no support for the hypothesis that speed of scanning for serial position information in immediate spatial memory leads to a relationship with articulation rate, nor is there any support for the view that memory span tasks in different domains share resources for dealing with serial order. The results are discussed in relation to Cowan, Keller, Hulme, Roodenrys, McDougall & Rack's (1994) suggestion that the relationship between articulation rate and memory span may be mediated by general processing speed.

Speed of memory scanning is not affected in early HIV-1 infection.

Thirty-seven nondemented HIV-seropositive and 17 seronegative control subjects were administered the Sternberg speed of memory scanning task, a procedure frequently employed to study mental slowing in patients with subcortical dementing disorders. Experimental and control subjects did not differ in speed of memory scanning, as indexed by the slopes of set size-reaction time functions, nor on mean 0-intercepts for the RT functions, which index stimulus detection and motor response time. Intercept values were significantly greater for subjects with a positive alcohol abuse history and for subjects with greater self-reported depression, but slopes were not significantly correlated with substance abuse history or psychological distress. Cognitive slowing in early HIV-1 infection is not a nonspecific effect observed across all measures of information processing speed. Underlying component functions measured must be carefully considered when selecting reaction time tasks for study with HIV-seropositive subjects. The term "subcortical" dementia may be too general a descriptor, and RT task performance may provide an alternative basis for classification of dementia types.

High‐speed memory scanning in Parkmson's disease: Adverse effects of levodopa

High-speed memory scanning as assessed by the Sternberg paradigm was studied in 12 nondemented patients with fluctuating Parkinson's disease and 13 age-matched healthy controls. Patients were first assessed before taking their morning dose of levodopa ("off") and again after that dose had produced full clinical effect ("on") after that dose had produced full clinical effect ("on"). Although motor components of the measured choice reaction time were slower in patients when off than in control subjects, memory scanning speed was not different. After levodopa (on), patients' motor time normalized, but cognitive processing speed became significantly slower when compared with previous performance in the off condition and with controls. Contrary to previous concepts of bradyphrenia in patients with Parkinson's disease, these results indicate that dopaminergic stimulation can reduce cognitive processing speed.

Memory scanning speed in language-disordered children.

Twelve students from classrooms for children with severe language disorders and 12 age-matched controls were evaluated for short-term memory scanning speed using the Sternberg task. Sets of two, three, and four digits were presented via earphones as memory sets, followed by single-probe digits. Reaction time was measured for a verbal response of "yes" or "no" indicating whether the probe was a member of the initial set. Average per-item scanning speed for the normal children was 66 ms, which was significantly different from the 253-ms average scanning speed of the language-disordered group. Many similarities were noted in the performance of the two groups on the memory scanning task. No differences were found in estimates of encoding and response speed, in percentage of errors or in serial or numerical position effects across groups. Results indicate that children with developmental language disorders may demonstrate reduced processing speed or memory retrieval time, which could contribute to linguistic deficits.

Memory scanning by children: Meaningfulness and mediation

Two experiments were performed for the purpose of isolating factors that influence speed of memory scanning by children. The first experiment revealed an interaction involving age and type of stimulus. Young children required relatively greater time to process ambiguous stimuli. The second experiment, involving a pretraining phase designed to induce mediation, showed that preschool children scan representations more rapidly when given instructions to apply a mediator.