Reverse Digit Span Research Articles

Does the right ear advantage persist in mature auditory systems when cognitive demand for processing increases?

Based on Kimura’s (1967) anatomical model of dichotic listening, the right ear has a slight advantage (REA) or performance asymmetry, compared with the left ear. This is due to left hemisphere dominance for language, which receives direct input from the right ear. Accurate performance on dichotic tests relies on sensory organization and memory; however, there is little evidence regarding the impact of increasing cognitive demands (i.e., number of items for recall) on auditory performance asymmetries in mature auditory systems. This study investigated 42 participants’ auditory perceptual and working memory abilities (e.g., forward and reverse digit spans, dichotic digits test, and directed ear dichotic digits test) to explore the relationships among cognitive demanded and performance asymmetries. Repeated measures ANOVA showed a significant effect for directed ear and digit list length. In addition, a priori comparison indicated significant performance asymmetry, with persistent REA when listening demands exceeded an individual’s auditory memory capacity. No significant performance differences were identified for digit list lengths relative to, or below an individual’s simple memory capacity. Overall, the study found the right ear tends to show better performance on dichotic listening tasks, even in adults, when the number of digits exceeded the participants’ digit span capacity.

Relating verbal and non-verbal auditory spans to language comprehension performance

Working memory capacity has often been assessed by various forms of the span task (e.g., reading span, digit span, etc.). Simple span tasks involve storage, whereas complex span tasks involve both storage and processing, and can include verbal and/or non-verbal stimuli. Arguably, daily activities, such as engaging in conversation or understanding a news article, require more storage and processing than recalling a list of numbers. The objective of this study was to determine the relationship of verbal and non-verbal auditory spans to language comprehension performance. Twenty-two normal-hearing adults participated in the study consisting of the following four experiments: forward and reverse digit span, Working Memory Span Task, Pitch Pattern Span Task, and the LISN (Lecture, Interview, and Spoken Narratives) listening comprehension task. Results revealed no significant relationship between non-verbal spans and language comprehension. Also, there was no significant relationship between forward and reverse digit spans to language comprehension. There was a significant correlation between the working memory span task and language comprehension. This suggests that complex language-based tasks that require more storage and processing will be better predictors of language comprehension than simple span tasks or tasks that do not involve language.

Verbal Working Memory in Older Adults: The Roles of Phonological Capacities and Processing Speed.

This study examined the potential roles of phonological sensitivity and processing speed in age-related declines of verbal working memory. Twenty younger and 25 older adults with age-normal hearing participated. Two measures of verbal working memory were collected: digit span and serial recall of words. Processing speed was indexed using response times during those tasks. Three other measures were also obtained, assessing phonological awareness, processing, and recoding. Forward and reverse digit spans were similar across groups. Accuracy on the serial recall task was poorer for older than for younger adults, and response times were slower. When response time served as a covariate, the age effect for accuracy was reduced. Phonological capacities were equivalent across age groups, so we were unable to account for differences across age groups in verbal working memory. Nonetheless, when outcomes for only older adults were considered, phonological awareness and processing speed explained significant proportions of variance in serial recall accuracy. Slowing in processing abilities accounts for the primary trajectory of age-related declines in verbal working memory. However, individual differences in phonological capacities explain variability among individual older adults.

The contribution of short-term memory capacity to reading ability in adolescents with cochlear implants

ObjectiveThis study aimed to establish the relationship between short-term memory capacity and reading skills in adolescents with cochlear implants. Methods and materialsA between-groups design compared a group of young people with cochlear implants with a group of hearing peers on measures of reading, and auditory and visual short-term memory capacity. The groups were matched for non-verbal IQ and age. The adolescents with cochlear implants were recruited from the Cochlear Implant Programme at a specialist children's hospital. The hearing participants were recruited from the same schools as those attended by the implanted adolescents. Participants were 18 cochlear implant users and 14 hearing controls, aged between 12 and 18 years. All used English as their main language and had no significant learning disability or neuro-developmental disorder.Short-term memory capacity was assessed in the auditory modality using Forward and Reverse Digit Span from the WISC IV UK, and visually using Forward and Reverse Memory from the Leiter-R. Individual word reading, reading comprehension and pseudoword decoding were assessed using the WIAT II UK. ResultsA series of ANOVAs revealed that the adolescents with cochlear implants had significantly poorer auditory short-term memory capacity and reading skills (on all measures) compared with their hearing peers. However, when Forward Digit Span was entered into the analyses as a covariate, none of the differences remained statistically significant. ConclusionsDeficits in immediate auditory memory persist into adolescence in deaf children with cochlear implants. Short-term auditory memory capacity is an important neurocognitive process in the development of reading skills after cochlear implantation in childhood that remains evident in later adolescence.

Biomarkers of a five-domain translational substrate for schizophrenia and schizoaffective psychosis.

BackgroundThe Mental Health Biomarker Project (2010–2014) selected commercial biochemistry markers related to monoamine synthesis and metabolism and measures of visual and auditory processing performance. Within a case–control discovery design with exclusion criteria designed to produce a highly characterised sample, results from 67 independently DSM IV-R-diagnosed cases of schizophrenia and schizoaffective disorder were compared with those from 67 control participants selected from a local hospital, clinic and community catchment area. Participants underwent protocol-based diagnostic-checking, functional-rating, biological sample-collection for thirty candidate markers and sensory-processing assessment.ResultsFifteen biomarkers were identified on ROC analysis. Using these biomarkers, odds ratios, adjusted for a case–control design, indicated that schizophrenia and schizoaffective disorder were highly associated with dichotic listening disorder, delayed visual processing, low visual span, delayed auditory speed of processing, low reverse digit span as a measure of auditory working memory and elevated levels of catecholamines. Other nutritional and biochemical biomarkers were identified as elevated hydroxyl pyrroline-2-one as a marker of oxidative stress, vitamin D, B6 and folate deficits with elevation of serum B12 and free serum copper to zinc ratio.When individual biomarkers were ranked by odds ratio and correlated with clinical severity, five functional domains of visual processing, auditory processing, oxidative stress, catecholamines and nutritional-biochemical variables were formed. When the strengths of their inter-domain relationships were predicted by Lowess (non-parametric) regression, predominant bidirectional relationships were found between visual processing and catecholamine domains. At a cellular level, the nutritional-biochemical domain exerted a pervasive influence on the auditory domain as well as on all other domains.ConclusionsThe findings of this biomarker research point towards a much-required advance in Psychiatry: quantification of some theoretically-understandable, translationally-informative, treatment-relevant underpinnings of serious mental illness. This evidence reveals schizophrenia and schizoaffective disorder in a somewhat different manner, as a conglomerate of several disorders many of which are not currently being assessed-for or treated in clinical settings. Currently available remediation techniques for these underlying conditions have potential to reduce treatment-resistance, relapse-prevention, cost burden and social stigma in these conditions. If replicated and validated in prospective trials, such findings will improve progress-monitoring and treatment-response for schizophrenia and schizoaffective disorder.

Evaluating visual and auditory contributions to the cognitive restoration effect

It has been suggested that certain real-world environments can have a restorative effect on an individual, as expressed in changes in cognitive performance and mood. Much of this research builds on Attention Restoration Theory (ART), which suggests that environments that have certain characteristics induce cognitive restoration via variations in attentional demands. Specifically, natural environments that require little top-down processing have a positive effect on cognitive performance, while city-like environments show no effect. We characterized the cognitive restoration effect further by examining (1) whether natural visual stimuli, such as blue spaces, were more likely to provide a restorative effect over urban visual stimuli, (2) if increasing immersion with environment-related sound produces a similar or superior effect, (3) if this effect extends to other cognitive tasks, such as the functional field of view (FFOV), and (4) if we could better understand this effect by providing controls beyond previous works. We had 202 participants complete a cognitive task battery, consisting of a reverse digit span task, the attention network task, and the FFOV task prior to and immediately after a restoration period. In the restoration period, participants were assigned to one of seven conditions in which they listened to natural or urban sounds, watched images of natural or urban environments, or a combination of both. Additionally, some participants were in a control group with exposure to neither picture nor sound. While we found some indication of practice effects, there were no differential effects of restoration observed in any of our cognitive tasks, regardless of condition. We did, however, find evidence that our nature images and sounds were more relaxing than their urban counterparts. Overall, our findings suggest that acute exposure to relaxing pictorial and auditory stimulus is insufficient to induce improvements in cognitive performance.

Effect of Fast and Slow Pranayama Practice on Cognitive Functions in Healthy Volunteers

To compare the cumulative effect of commonly practised slow and fast pranayama on cognitive functions in healthy volunteers. 84 participants who were in self-reported good health, who were in the age group of 18-25 years, who were randomized to fast pranayama, slow pranayama and control group with 28 participants in each group. Fast pranayama included kapalabhati, bhastrika and kukkuriya. Slow pranayama included nadishodhana, Pranav and Savitri. Respective pranayama training was given for 35 minutes, three times per week, for a duration of 12 weeks under the supervision of a certified yoga trainer. Parameters were recorded before and after 12 weeks of intervention: Perceived stress scale (PSS), BMI, waist to hip ratio and cognitive parameters-letter cancellation test, trail making tests A and B, forward and reverse digit spans and auditory and visual reaction times for red light and green light. Inter-group comparison was done by one way ANOVA and intra-group comparison was done by paired t-test. Executive functions, PSS and reaction time improved significantly in both fast and slow pranayama groups, except reverse digit span, which showed an improvement only in fast pranayama group. In addition, percentage reduction in reaction time was significantly more in the fast pranayama group as compared to that in slow pranayama group. Both types of pranayamas are beneficial for cognitive functions, but fast pranayama has additional effects on executive function of manipulation in auditory working memory, central neural processing and sensory-motor performance.

EPA-0010 – The “Double Whammy Effect” Of Combined Smoking And Drinking Upon Everyday Prospective Memory And Executive Function

Introduction Excessive alcohol use and persistent smoking have both been found independently to have a deleterious impact upon prospective memory (PM: memory for planning and executing future activities) and executive function (EF: the control of attention in memory) in the past. Aims The present study examined whether those who simultaneously drank alcohol and smoked were at greater risk of PM and EF deficits compared with an alcohol-only group and a zero-substance user group. Methods Anyone reporting using illegal substances (e.g. ecstasy/cannabis) were excluded. 23 poly-drug users (PD: those who drank and smoked), 27 single drug users (SD: who only drank alcohol) and 29 zero-users (ZU: who did not use any recreational drug) were compared on measures of anxiety, depression, PM and EF. PM was measured using a virtual reality PM task (VRPMT) in which the participant had to recall specific activities at particular locations when navigating though the computer-based virtual reality ‘office’ environment. EF was measured using the Reverse Digit Span (RDS) which required the participant to recall increasing numbers of digits in reverse order. Results There were no significant between-group differences in terms of gender, age, alcohol use (PD and SD only), anxiety, or depression scores. The PD group performed the worst on the VRPMT and RDS tasks; followed by the SD group; with highest performance on these tasks being observed in the ZU group. Conclusions Combined drinking and smoking produces a kind of ‘double whammy effect’ on PM and EF, compared with single drug-use and zero-user groups.

Comparison of Two Working Memory Test Paradigms: Correlation with Academic Performance in School-Aged Children

The purpose of this study was to examine the relationship between two different working memory task paradigms and academic achievement. Participants were 202 Australian primary-school children who were assessed on the Complex Auditory Span Evaluation (CASE) - a dual-task paradigm - and a reverse digit span paradigm, the number memory reversed test (NMR). Performance was correlated against the participants’ National Assessment Program - Literacy and Numeracy (NAPLAN) results. Both the CASE and NMR were significant predictors of academic ability in literacy and numeracy. Whereas there was a significant correlation between the CASE and NMR, the relationship was weak (r=0.18, p=0.012). It was concluded that, although both types of test are related to academic achievement, NMR and dual-task paradigm tasks may be differentially sensitive to the working memory abilities required in different real-world situations. This result has implications for use of such tasks to predict academic performance.

Adverse health effects of occupational exposure to radiofrequency radiation in airport surveillance radar operators

Introduction:Radar workers are exposed to pulsed high frequency electromagnetic fields. In this study, health effects of these radiations in personnel who routinely work with radar systems are investigated.Materials and Methods:The 28-item General Health Questionnaire was used as a self-administered tool for assessment of general mental health and mental distress. One hundred workers occupationally exposed to radar radiations (14-18 GHz) participated in the study. Visual reaction time was recorded with a simple blind computer-assisted-visual reaction time test. To assess the short-term memory, Wechsler Memory Scale-III test was performed.Results:Twenty to 39% of the radar workers reported different problems such as needing a good tonic, feeling run down and out of sorts, headache, tightness or pressure in the head, insomnia, getting edgy and bad-tempered. Furthermore, 47% of the radar workers reported feeling under strain. In response to this question that if they have been able to enjoy their normal day-to-day activities, 31% responded less than usual. It was also shown that work experience had significant relationships with reaction time and short-term memory indices i.e., forward digit span, reverse digit span, word recognition and paired words.Conclusion:To the best of our knowledge, this is the first study to show that occupational exposure to radar microwave radiation leads to changes in somatic symptoms, anxiety and insomnia, social dysfunction, and severe depression. Altogether these results indicate that occupational exposure to radar microwave radiations may be linked to some adverse health effects.

A Combined Early Cognitive and Physical Rehabilitation Program for People Who Are Critically Ill: The Activity and Cognitive Therapy in the Intensive Care Unit (ACT-ICU) Trial

In the coming years, the number of survivors of critical illness is expected to increase. These survivors frequently develop newly acquired physical and cognitive impairments. Long-term cognitive impairment is common following critical illness and has dramatic effects on patients' abilities to function autonomously. Neuromuscular weakness affects similar proportions of patients and leads to equally profound life alterations. As knowledge of these short-term and long-term consequences of critical illness has come to light, interventions to prevent and rehabilitate these devastating consequences have been sought. Physical rehabilitation has been shown to improve functional outcomes in people who are critically ill, but subsequent studies of physical rehabilitation after hospital discharge have not. Post-hospital discharge cognitive rehabilitation is feasible in survivors of critical illness and is commonly used in people with other forms of acquired brain injury. The feasibility of early cognitive therapy in people who are critically ill remains unknown. The purpose of this novel protocol trial will be to determine the feasibility of early and sustained cognitive rehabilitation paired with physical rehabilitation in patients who are critically ill from medical and surgical intensive care units. This is a randomized controlled trial. The setting for this trial will be medical and surgical intensive care units of a large tertiary care referral center. The participants will be patients who are critically ill with respiratory failure or shock. Patients will be randomized to groups receiving usual care, physical rehabilitation, or cognitive rehabilitation plus physical rehabilitation. Twice-daily cognitive rehabilitation sessions will be performed with patients who are noncomatose and will consist of orientation, memory, and attention exercises (eg, forward and reverse digit spans, matrix puzzles, letter-number sequences, pattern recognition). Daily physical rehabilitation sessions will advance patients from passive range of motion exercises through ambulation. Patients with cognitive or physical impairment at discharge will undergo a 12-week, in-home cognitive rehabilitation program. A battery of neurocognitive and functional outcomes will be measured 3 and 12 months after hospital discharge. If feasible, these interventions will lay the groundwork for a larger, multicenter trial to determine their efficacy.

Alteraciones de funciones cognitivas y ejecutivas en pacientes dependientes de cocaína: estudio de casos y controles

In the past, various studies have related chronic cocaine use to diverse types of neuropsychological impairment. However, the majority of these studies offer partial results using batteries of tests of little ecological weight.To investigate neuropsychological impairment (and of executive functions in particular) amongst severe chronic cocaine users, measured by means of more ecological tests and in a more global manner, taking confounding factors into account, such as age, years of schooling, gender, race, opioid dependence and alcohol consumption.We performed an observational study, comparing the cocaine dependence group (n = 24) with a non-cocaine use control group (n = 27).The principal results revealed significant differences in the direct and reverse digit span tests (p = 0.008 and p < 0.001 respectively), and in the Cards Test (p < 0.001). They also showed a significance result in the Zoo Map Test (p = 0.001), and in different measurements but not in all forming part of the Wisconsin test (number of correct responses and number of errors).These results confirm that the chronic use of cocaine per se causes neuropsychological impairment that is manifested in classical and ecologically-valid tests. This impairment may influence patients' functionality and prognosis, and also therapeutic failure.

P-38 - The impact of ecstasy upon prospective memory and related central executive processes

The prolonged use of MDMA or ‘ecstasy’ has been associated with a range of memory deficits, including impairments in prospective memory (PM: remembering future activities or events). What is not clear is the extent to which ecstasy users' PM problems might be underpinned by more general central executive problems within memory (CE: a set of processes underpinning the organisation and flow of information within memory). The present study extended this research by examining whether persistent use of ecstasy damages prospective memory independent of CE. An existing-groups design was utilised, comparing ecstasy users with a non-user group as the independent factor. Scores on the Cambridge Prospective Memory Test (CAMPROMPT: an objective measure of time- and event- based PM) constituted the PM dependent measure and scores on the Reverse Digit Span task (RDS: an objective CE task) constituted the CE dependent measure. Age, mood, and other drug use (alcohol, smoking, cannabis) were also measured. After observing no between-group differences on age, mood, and other drug use, ecstasy users performed significantly worse on the CAMPROMPT and RDS than did the non-users. After controlling for RDS scores, the difference between users and non-users on CAMPROMPT disappeared. The finding that ecstasy users showed reduced performance on the CAMPROMPT after controlling for CE performance suggests strongly that objective PM performance is underpinned by CE functions, suggesting CE deficits may be at the heart of ecstasy-related PM deficits.

Comparative study of OROS-MPH and atomoxetine on executive function improvement in ADHD: a randomized controlled trial

This study aimed to compare the effects of osmotic release oral system-methylphenidate (OROS-MPH) and atomoxetine (ATX) on executive function in children and adolescents with attention deficit hyperactivity disorder (ADHD) by a randomized controlled trial. Subjects who met DSM-IV ADHD criteria were randomized to receive either OROS-MPH or ATX treatment. The doses were titrated to achieve optimal response and then maintained for 4-6 wk. A battery of executive function tests and the Behavior Rating Inventory of Executive Function (BRIEF) were administered to subjects who completed the dose titration (OROS-MPH, n=85; ATX, n=57) at the pre- and post-treatment periods. Forty-six children without ADHD were recruited as controls. Both OROS-MPH and ATX significantly improved scores in the Rey Complex Figure Test (RCFT), digit span, and Stroop color-word task. The scores in RCFT and the reverse digit span were not significantly different from the control group at post-treatment assessment (OROS-MPH=ATX=control, p>0.05), whereas the word interference time of the Stroop test was still more than that of the control group (OROS-MPH=ATX>control, p>0.05). OROS-MPH also significantly improved the total correct response in the verbal fluency test to normal level, and the shifting time in the trail-making test to subnormal level. The current findings suggest both OROS-MPH and ATX improved executive function generally in children and adolescents with ADHD, and could return working memory back to normative performance level.

A short self-report measure of problems with executive function suitable for administration via the Internet

This article describes a short self-report measure of problems with executive function designed for use in Internet-mediated research. In Study 1, participants completed the online measure (Webexec) using a browser but under laboratory conditions. They also completed a paper self-report measure of executive problems (the Dysexecutive Questionnaire; DEX) and three objective tasks involving executive function: reverse digit span, semantic fluency (unconstrained), and semantic fluency (constrained). Webexec scores correlated positively with the DEX and negatively with the three executive tasks. Further evidence of construct validity came from Study 2, in which Webexec scores correlated positively with both use of cannabis and prospective memory problems reported in an online drug questionnaire. Webexec thus appears suitable for online research with normal populations.

Accuracy of neuropsychological tests and the Neuropsychiatric Inventory in differential diagnosis between Frontotemporal dementia and Alzheimer's disease.

The differential diagnosis between frontotemporal dementia (FTD) and Alzheimer’s disease (AD) is sometimes difficult.ObjectivesTo verify the accuracy of neuropsychological tests and a behavioral disorders scale in the differential diagnosis between FTLD and AD.MethodsRetrospective data on 12 FTD patients and 12 probable AD patients were analyzed. The scores on neuropsychological tests (MMSE score, reverse digit span, delayed recall for drawings, semantic fluency of animals) and the Neuropsychiatric Inventory (NPI) in both groups were compared.ResultsBoth groups had similar performance on neuropsychological tests. All FTD patients and 50% of AD patients had neuropsychiatric abnormalities. The NPI score was 58.0±19.3for the FTD patients, and 3.6±4.7for the AD patients (p< 0.01). Using a NPI cut-off score of 13, the sensitivity and specificity were 100% in this sample. The four most common neuropsychiatric disturbances in FTD patients were: apathy, aberrant motor behavior, disinhibition and eating abnormalities. Apathy and dysphoria/depression were the most common behavioral symptoms among the AD patients.ConclusionsIn this study, NPI was found to be a useful tool for the differential diagnosis between FTD and AD. The neuropsychological tests commonly used in the medical office were unable to distinguish between the two groups.

Abnormal auditory ERP N100 in children with dyslexia: comparison with their control siblings

BackgroundRecent research has implicated deficits of the working memory (WM) and attention in dyslexia. The N100 component of event-related potentials (ERP) is thought to reflect attention and working memory operation. However, previous studies showed controversial results concerning the N100 in dyslexia. Variability in this issue may be the result of inappropriate match up of the control sample, which is usually based exclusively on age and gender.MethodsIn order to address this question the present study aimed at investigating the auditory N100 component elicited during a WM test in 38 dyslexic children in comparison to those of 19 unaffected sibling controls. Both groups met the criteria of the International Classification of Diseases (ICD-10). ERP were evoked by two stimuli, a low (500 Hz) and a high (3000 Hz) frequency tone indicating forward and reverse digit span respectively.ResultsAs compared to their sibling controls, dyslexic children exhibited significantly reduced N100 amplitudes induced by both reverse and forward digit span at Fp1, F3, Fp2, Fz, C4, Cz and F4 and at Fp1, F3, C5, C3, Fz, F4, C6, P4 and Fp2 leads respectively. Memory performance of the dyslexics group was not significantly lower than that of the controls. However, enhanced memory performance in the control group is associated with increased N100 amplitude induced by high frequency stimuli at the C5, C3, C6 and P4 leads and increased N100 amplitude induced by low frequency stimuli at the P4 lead.ConclusionThe present findings are in support of the notion of weakened capture of auditory attention in dyslexia, allowing for a possible impairment in the dynamics that link attention with short memory, suggested by the anchoring-deficit hypothesis.

Attention control, memory updating, and emotion regulation temporarily reduce the capacity for executive control.

This research tested the hypothesis that initial efforts at executive control temporarily undermine subsequent efforts at executive control. Four experiments revealed that controlling the focus of visual attention (Experiment 1), inhibiting predominant writing tendencies (Experiment 2), taking a working memory test (Experiment 3), or exaggerating emotional expressions (Experiment 4) undermined performance on subsequent tests of working memory span, reverse digit span, and response inhibition, respectively. The results supported a limited resource model of executive control and cast doubt on competing accounts based on mood, motivation, or task difficulty. Prior efforts at executive control are a significant contextual determinant of the operation of executive processes.

EEG MARKERS FOR COGNITIVE DECLINE IN ELDERLY SUBJECTS WITH SUBJECTIVE MEMORY COMPLAINTS

New treatments for Alzheimer's disease require early detection of cognitive decline. Most studies seeking to identify markers of early cognitive decline have focused on a limited number of measures. We sought to establish the profile of brain function measures which best define early neuropsychological decline. We compared subjects with subjective memory complaints to normative controls on a wide range of EEG derived measures, including a new measure of event-related spatio-temporal waves and biophysical modeling, which derives anatomical and physiological parameters based on subject's EEG measurements. Measures that distinguished the groups were then related to cognitive performance on a variety of learning and executive function tasks. The EEG measures include standard power measures, peak alpha frequency, EEG desynchronization to eyes-opening, and global phase synchrony. The most prominent differences in subjective memory complaint subjects were elevated alpha power and an increased number of spatio-temporal wave events. Higher alpha power and changes in wave activity related most strongly to a decline in verbal memory performance in subjects with subjective memory complaints, and also declines in maze performance and working memory reaction time. Interestingly, higher alpha power and wave activity were correlated with improved performance in reverse digit span in the subjective memory complaint group. The modeling results suggest that differences in the subjective memory complaint subjects were due to a decrease in cortical and thalamic inhibitory gains and slowed dendritic time-constants. The complementary profile that emerges from the variety of measures and analyses points to a nonlinear progression in electrophysiological changes from early neuropsychological decline to late-stage dementia, and electrophysiological changes in subjective memory complaint that vary in their relationships to a range of memory-related tasks.

Commentary on Early Identification and Intervention for Students With Mathematics Difficulties

_ This article highlights key findings from the small body of research on mathematics difficulties (MD) relevant to early identification and early intervention. The research demonstrates that (a) for many children, mathematics difficulties are not stable over time; (b) the presence of reading difficulties seems related to slower progress in many aspects of mathematics; (c) almost all students with MD demonstrate problems with accurate and automatic retrieval of basic arithmetic combinations, such as 6 + 3. The following measures appear to be valid and reliable indicators of potential MD in kindergartners: (a) magnitude comparison (i.e., knowing which digit in a pair is larger), (b) sophistication of counting strategies, (c) fluent identification of numbers, and (d) working memory (as evidenced by reverse digit span). These are discussed in terms of the components of number sense. Implications for early intervention strategies are explored.