Monica Melby-Lervåg

Is working memory training effective? A meta-analytic review

It has been suggested that working memory training programs are effective both as treatments for attention-deficit/hyperactivity disorder (ADHD) and other cognitive disorders in children and as a tool to improve cognitive ability and scholastic attainment in typically developing children and adults. However, effects across studies appear to be variable, and a systematic meta-analytic review was undertaken. To be included in the review, studies had to be randomized controlled trials or quasi-experiments without randomization, have a treatment, and have either a treated group or an untreated control group. Twenty-three studies with 30 group comparisons met the criteria for inclusion. The studies included involved clinical samples and samples of typically developing children and adults. Meta-analyses indicated that the programs produced reliable short-term improvements in working memory skills. For verbal working memory, these near-transfer effects were not sustained at follow-up, whereas for visuospatial working memory, limited evidence suggested that such effects might be maintained. More importantly, there was no convincing evidence of the generalization of working memory training to other skills (nonverbal and verbal ability, inhibitory processes in attention, word decoding, and arithmetic). The authors conclude that memory training programs appear to produce short-term, specific training effects that do not generalize. Possible limitations of the review (including age differences in the samples and the variety of different clinical conditions included) are noted. However, current findings cast doubt on both the clinical relevance of working memory training programs and their utility as methods of enhancing cognitive functioning in typically developing children and healthy adults.

Phonological skills and their role in learning to read: A meta-analytic review.

The authors report a systematic meta-analytic review of the relationships among 3 of the most widely studied measures of childrens phonological skills (phonemic awareness, rime awareness, and verbal short-term memory) and childrens word reading skills. The review included both extreme group studies and correlational studies with unselected samples (235 studies were included, and 995 effect sizes were calculated). Results from extreme group comparisons indicated that children with dyslexia show a large deficit on phonemic awareness in relation to typically developing children of the same age (pooled effect size estimate: -1.37) and children matched on reading level (pooled effect size estimate: -0.57). There were significantly smaller group deficits on both rime awareness and verbal short-term memory (pooled effect size estimates: rime skills in relation to age-matched controls, -0.93, and reading-level controls, -0.37; verbal short-term memory skills in relation to age-matched controls, -0.71, and reading-level controls, -0.09). Analyses of studies of unselected samples showed that phonemic awareness was the strongest correlate of individual differences in word reading ability and that this effect remained reliable after controlling for variations in both verbal short-term memory and rime awareness. These findings support the pivotal role of phonemic awareness as a predictor of individual differences in reading development. We discuss whether such a relationship is a causal one and the implications of research in this area for current approaches to the teaching of reading and interventions for children with reading difficulties.

Working Memory Training Does Not Improve Performance on Measures of Intelligence or Other Measures of “Far Transfer” Evidence From a Meta-Analytic Review

It has been claimed that working memory training programs produce diverse beneficial effects. This article presents a meta-analysis of working memory training studies (with a pretest-posttest design and a control group) that have examined transfer to other measures (nonverbal ability, verbal ability, word decoding, reading comprehension, or arithmetic; 87 publications with 145 experimental comparisons). Immediately following training there were reliable improvements on measures of intermediate transfer (verbal and visuospatial working memory). For measures of far transfer (nonverbal ability, verbal ability, word decoding, reading comprehension, arithmetic) there was no convincing evidence of any reliable improvements when working memory training was compared with a treated control condition. Furthermore, mediation analyses indicated that across studies, the degree of improvement on working memory measures was not related to the magnitude of far-transfer effects found. Finally, analysis of publication bias shows that there is no evidential value from the studies of working memory training using treated controls. The authors conclude that working memory training programs appear to produce short-term, specific training effects that do not generalize to measures of “real-world” cognitive skills. These results seriously question the practical and theoretical importance of current computerized working memory programs as methods of training working memory skills.

Language and verbal short-term memory skills in Children with Down syndrome :A meta-analytic review

This study presents a meta-analytic review of language and verbal short-term memory skills in children with Down syndrome. The study examines the profile of strengths and weaknesses in children with Down syndrome compared to typically developing children matched for nonverbal mental age. The findings show that children with Down syndrome have broad language deficits (that are not restricted to measures of expressive language) and associated verbal short-term memory deficits. The profile of language skills in children with Down syndrome shows similarities to that seen in children with Specific Language Impairment. The practical and theoretical implications of these findings are discussed.

There is no convincing evidence that working memory training is effective: A reply to Au et al. (2014) and Karbach and Verhaeghen (2014)

The possible cognitive benefits of working memory training programs have been the subject of intense interest and controversy. Recently two meta-analyses have claimed that working memory training can be effective in enhancing cognitive skills in adulthood (Au et al. Behavioural Brain Research 228:(1) 107-115, 2014) and stemming cognitive decline in old age (Karbach & Verhaeghen Psychological Science 25:2027–2037, 2014). The current article critically evaluates these claims. We argue that these meta-analyses produce misleading results because of (1) biases in the studies included, (2) a failure to take account of baseline differences when calculating effect sizes, and (3) a failure to emphasize the difference between studies with treated versus untreated control groups. We present new meta-analyses and conclude that there is no convincing evidence that working memory training produces general cognitive benefits.

Reading Comprehension and its Underlying Components in Second Language Learners: A Meta-analysis of Studies Comparing First and Second Language Learners

We report a systematic meta-analytic review of studies comparing reading comprehension and its underlying components (language comprehension, decoding, and phonological awareness) in first- and second-language learners. The review included 82 studies, and 576 effect sizes were calculated for reading comprehension and underlying components. Key findings were that, compared to first-language learners, second-language learners display a medium-sized deficit in reading comprehension (pooled effect size d = -0.62), a large deficit in language comprehension (pooled effect size d = -1.12), but only small differences in phonological awareness (pooled effect size d = -0.08) and decoding (pooled effect size d = -0.12). A moderator analysis showed that characteristics related to the type of reading comprehension test reliably explained the variation in the differences in reading comprehension between first- and second-language learners. For language comprehension, studies of samples from low socioeconomic backgrounds and samples where only the first language was used at home generated the largest group differences in favor of first-language learners. Test characteristics and study origin reliably contributed to the variations between the studies of language comprehension. For decoding, Canadian studies showed group differences in favor of second-language learners, whereas the opposite was the case for U.S. studies. Regarding implications, unless specific decoding problems are detected, interventions that aim to ameliorate reading comprehension problems among second-language learners should focus on language comprehension skills.

Oral language deficits in familial dyslexia: A meta-analysis and review.

This article reviews 95 publications (based on 21 independent samples) that have examined children at family risk of reading disorders. We report that children at family risk of dyslexia experience delayed language development as infants and toddlers. In the preschool period, they have significant difficulties in phonological processes as well as with broader language skills and in acquiring the foundations of decoding skill (letter knowledge, phonological awareness and rapid automatized naming [RAN]). Findings are mixed with regard to auditory and visual perception: they do not appear subject to slow motor development, but lack of control for comorbidities confounds interpretation. Longitudinal studies of outcomes show that children at family risk who go on to fulfil criteria for dyslexia have more severe impairments in preschool language than those who are defined as normal readers, but the latter group do less well than controls. Similarly at school age, family risk of dyslexia is associated with significantly poor phonological awareness and literacy skills. Although there is no strong evidence that children at family risk are brought up in an environment that differs significantly from that of controls, their parents tend to have lower educational levels and read less frequently to themselves. Together, the findings suggest that a phonological processing deficit can be conceptualized as an endophenotype of dyslexia that increases the continuous risk of reading difficulties; in turn its impact may be moderated by protective factors.

Sentence repetition is a measure of children's language skills rather than working memory limitations

Sentence repetition tasks are widely used in the diagnosis and assessment of children with language difficulties. This paper seeks to clarify the nature of sentence repetition tasks and their relationship to other language skills. We present the results from a 2-year longitudinal study of 216 children. Children were assessed on measures of sentence repetition, vocabulary knowledge and grammatical skills three times at approximately yearly intervals starting at age 4. Sentence repetition was not a unique longitudinal predictor of the growth of language skills. A unidimensional language latent factor (defined by sentence repetition, vocabulary knowledge and grammatical skills) provided an excellent fit to the data, and language abilities showed a high degree of longitudinal stability. Sentence repetition is best seen as a reflection of an underlying language ability factor rather than as a measure of a separate construct with a specific role in language processing. Sentence repetition appears to be a valuable tool for language assessment because it draws upon a wide range of language processing skills.

Nonword-Repetition Ability Does Not Appear to Be a Causal Influence on Children’s Vocabulary Development

In the study reported here, we assessed the theory that vocabulary learning in children depends critically on the capacity of a “phonological loop” that is indexed by nonword-repetition ability. A 3-year longitudinal study of 219 children assessed nonword-repetition ability and vocabulary knowledge at yearly intervals between the ages of 4 and 7 years. There was a considerable degree of longitudinal stability in children’s vocabulary and nonword-repetition skills, but there was no evidence of any influence of nonword-repetition ability on later vocabulary knowledge. These results seriously call into question the claim that vocabulary learning in children is constrained by nonword-repetition ability, and they cast doubt on the broader theory that the phonological loop functions as a language-learning device.

Oral Language Skills Moderate Nonword Repetition Skills in Children With Dyslexia: A Meta-Analysis of the Role of Nonword Repetition Skills in Dyslexia

We present a meta-analysis reviewing studies that have focused on the relationship between dyslexia and nonword repetition. The results show that children with dyslexia have poorer nonword repetition skills when compared to both chronological-age and reading-level controls. However, the severity of the nonword repetition problem varies significantly between studies, and the most important predictor of this variability is oral language skills. We argue that the sizable explanatory value of oral language skills reflects sample variation in the rate of comorbidity between dyslexia and specific language disorders. Thus, samples with combined dyslexia and specific language disorders demonstrate the most severe nonword repetition problems.