Cognitive deficits in reading disability and attention deficit disorder

This paper presents data from three studies (a cross-sectional study of school-referred children, a test-retest study of subtypes of reading disabilities, and a study of a large, random sample of first graders) that focus on specifying the cognitive deficits associated with reading difficulties and separating them from those associated with attentional deficits. The cognitive deficits associated with difficulty in reading were consistent across samples, developmental levels, definitions, and subtypes of reading disabilities. With IQ, age, and sex controlled for, poor readers were significantly impaired on measures of naming and phonological awareness. The effects of attentional deficits were more variable and complex but were clearly separate from the reading disability effects.     

Attention deficit disorder: A review of literature

A review of current and available literature tends to suggest that the search for identifying universal and specific features of handicapping conditions continues, as disagreement emerges over the construct of Attention Deficit Disorder. This paper attempts to summarize the debate in professional literature regarding the definitions, implications, diagnosis, and future research of Attention Deficit Disorder with and without hyperactivity.     

Attention deficit disorders: characteristics,assessment, and interventions

ABSTRACT

In the United States, there is an increasing prevalence of children who are diagnosed with an attention deficit disorder (ADD). The essential features of ADD are developmentally inappropriate degrees of inattention, impulsivity, and motor hyperactivity. The rate of prevalence could differ in other countries depending on the definition of the condition. This article will review related research in the United States about ADD which will include the following topics: differential diagnosis and assessment, treatment, interventions, and parent training. The overlap of ADD with other handicaps will be described as well as assessment techniques such as interviews, rating scales, and observations. Studies of the efficacy of medication, educational interventions, cognitive‐behavioral strategies, and parent training are reviewed. In the conclusion, suggestions for further research are outlined which may further assist youngsters with ADD to adjust at school, in the home, and in the community.     

Taxonomic separation of attention deficit disorders and developmental reading disorders

This investigation compared the behavior ratings and psychometric profiles of children with attention deficit disorders (ADD) and children with developmental reading disorders (DRD). ADD children showed no qualitative reading or spelling problems, although they were slightly behind expected levels of academic achievement. DRD children were significantly more impaired in academic attainment and showed evidence of qualitative disturbances in reading and spelling. DRD subjects did not differ from control subjects on ratings of hyperactivity, which was one of the defining variables of the ADD group. This evidence is interpreted as adding to a growing testimony that indicates that ADD and DRD are distinctly separate groups of disorders.     

The etiological relationship between reading disability and phonological disorder

The present study investigated the etiological relationship between two disorders: dyslexia or reading disability (RD) and phonological disorder (PD). These disorders manifest at different ages and have typically been studied by researchers in different disciplines. However, a growing body of evidence suggests that the disorders overlap at symptomatic, cognitive, and etiological levels of analysis. In previous studies, each disorder has been found to be heritable, and there is also evidence that RD and PD run together in families, but no studies to date have documented whether there is a shared genetic influence between the two disorders. The present study examined this question in a sample of RD and non-RD twins. Subjects with a history of PD were identified and the etiological relation between the two disorders was examined. Results indicated that in the present sample, RD and PD are each heritable on their own. Further, even when correcting for RD, the two disorders were found to be coheritable, indicating that the finding of cofamiliality of RD and PD is at least partially driven by genetic influences. The implications of these results for the conceptualization, identification, and treatment of these two disorders are discussed.     

Motor correlates of ADHD: contribution of reading disability and oppositional defiant disorder

This study investigated whether the likelihood of motor impairment in children with attention-deficit/hyperactivity disorder (ADHD) increases with the presence of other disorders, and whether the co-occurring diagnoses of reading disability (RD) and oppositional defiant disorder (ODD) account for the motor deficits seen in ADHD. A total of 291 children (218 boys, 73 girls) participated. Six groups of children were compared: ADHD only (n = 29); RD only (n = 63); ADHD and RD (n = 47); ADHD and ODD (n = 19); ADHD, RD, and ODD (n = 21); and typically developing control children (n = 112). Motor skills were assessed with the Bruininks-Oseretsky Test of Motor Proficiency and the Beery Test of Visual-Motor Integration. We found that the motor skills of the ADHD-only group did not differ from the typical control group. Furthermore, motor impairment in ADHD increased as a function of co-occurring disorders, and the presence of RD rather than ADHD predicted motor impairment.     

Why the timing deficit hypothesis does not explain reading disability in adults

It has been proposed that the phonological coredeficit that is linked to reading failure hasas its underlying cause a deficit in temporalprocessing. In a multivariate investigationdesigned to examine the temporal processingdeficit hypothesis, thirty reading-disabled(RD) adults, thirty-two normally achievingadults and thirty-one normally achievingchildren (reading-level controls) wereadministered a comprehensive battery thatincluded a wide range of timing tasks, inaddition to reading and phonological measures. Although adults with RD displayed overallperformance that was below that of normallyachieving adults on most of the timing tasks,their performance was not differentiallyinfluenced by rate of stimulus presentation. Although the RD adults displayed the typicalpattern of impaired phonological awareness andpseudoword reading relative to reading-levelmatched children, the reading-disabled adultsoutperformed the children on the timing tasks. Finally, with the exception of continuousnaming, the timing tasks shared little variancewith phonological sensitivity and contributedlittle unique variance to word reading. Although these findings undermine the timingdeficit hypothesis, they do provide evidencefor the involvement of naming deficits inreading disability.     

Attention deficit disorder with and without hyperactivity: reaction time and speed of cognitive processing

This study addressed the issue as to whether children reliably diagnosed as attention deficit disordered with hyperactivity (ADD/H) and without hyperactivity (ADD/WO) differed significantly from each other and a clinic control (CC) population on speed and efficiency of cognitive processing. From an outpatient clinic population, 43 ADD/H and 22 ADD/WO children were examined. An analysis of mean reaction time and speeded classification task performance revealed significant group effects on both mean reaction time and on a measure of within-subject variability. ADD/H children performed significantly more slowly and variably than the CC children on several of the speeded classification tasks. However, the ADD/WO group was not distinguished on any measure. Thus, while children may be reliably diagnosed as ADD/H or ADD/WO using behavioral measures, it would appear that they cannot be distinguished on these neurocognitive tasks. Issues related to childhood psychopathology and the neuropsychological basis of ADD/H are discussed.     

Comorbidity of reading disability and attention-deficit/hyperactivity disorder: differences by gender and subtype

This study used a community sample of 494 twins with a reading disability (223 girls, 271 boys) and 373 twins without a reading disability (189 girls, 184 boys) to assess the relation between reading disability (RD) and attention-deficit/hyperactivity disorder (ADHD). Symptoms of DSM-III and DSM-IV ADHD were classified into symptoms of inattention and symptoms of hyperactivity-impulsivity (H/I). Results indicated that individuals with RD were more likely than individuals without RD to meet criteria for ADHD and that the association between RD and ADHD was stronger for symptoms of inattention than for symptoms of H/I. Parents and teachers reported similar rates of ADHD, suggesting that ADHD symptoms were pervasive across settings and were not solely attributable to academic frustration. Analyses of possible gender differences revealed that RD was significantly associated with inattention in both girls and boys but associated with H/I only in boys. This difference may provide a partial explanation for the discrepancy between the gender ratio obtained in referred (approximately 4 boys to 1 girl) and nonreferred (1.2 to 1.5 boys to 1 girl) samples of individuals with RD. Specifically, the hyperactive and impulsive behaviors exhibited by boys with RD may be more disruptive than the inattentive behaviors exhibited by girls and may therefore precipitate more frequent referrals for clinical attention.     

The search for subtypes of specific reading disability: Reflections from a cognitive perspective

An overview of the literature on developmental dyslexia is offered, moving historically from attempts to identify a single underlying deficit to more recent efforts to define different subtypes of this developmental disorder. Two approaches to the subtyping problem are illustrated and briefly discussed. It is suggested that many of the remaining questions in dyslexia research could be more profitably addressed within the context of a coherent model of reading behaviour. In the latter half of this review, the potential implications of some aspects of the interactive reading theories for the study of reading dysfunction are explored. Preparation of this review was supported by funds from the Medical Research Council of Canada, the Ontario Mental Health Foundation/COMSOC Provincial Lottery Grants Program, and The Hospital for Sick Children Foundation.     

Specific reading disability: Follow-up studies

Twenty-four children with specific reading disability, originally studied and treated at the Bellevue Hospital Mental Hygiene Clinic between 1949 and 1951, were reexamined as young adults between 1961 and 1962 with the battery of tests given to them ten to 12 years before. Their specific perceptual problems and evidence of lack of clear- out cerebral dominance persists, although in less severe form. Those patients who as children had neurological signs in addition to the specific reading disability showed less improvement than those who had none.     

Familial patterns of expression of specific reading disability in a population sample

Summary A sample school population of 75 family units of equal size was investigated for expression of specific reading disability. 25.3% of the total children showed specific reading disability as defined in this study. By using spelling achievement as the criterion for the presence of the disability, the incidence of the disorder was shown to be much higher in certain families than in others, with clear sibling aggregation. The siblings of specific-reading-disability cases demonstrated lower spelling competence than the total siblings in normal families, even when well above a crippling level. Both within individual families and by grades, the spelling rating in relation to grade norms of the specific-reading-disability family cases with their siblings tended to decline with age, in contrast to normal families where it tended to improve with age. This pattern was even more striking if the greater language competence of females, now quite generally accepted and further supported by this study, was taken into account. It was demonstrated that the above patterns were not primarily a product of intelligence level or teaching methods. The bearing of these findings on the tenability of the most common, current hypotheses concerning causation was briefly discussed. From the Language Clinic and Division of Neurology, Massachusetts General Hospital.     

Temporal processing and reading disability

The present investigation examined thehypothesis that early auditory temporalprocessing deficits cause later specificreading disability by impairing phonologicalprocessing (Farmer & Klein 1995; Tallal1980, 1984). Temporal processing ability atschool entry was examined using Tallal'sRepetition Test in a large unselected sample ofover 500 children followed over subsequentyears. Although our data confirmed the presenceof certain non-speech auditory processingdeficits in children later classified asspecific reading-disabled, many findings wereclearly at odds with a causal interpretation ofthis relationship. (1) Reading-disabled (RD)children were impaired at school entry on thesubtest with long interstimulus intervals(ISIs) but not the critical short-ISIsubtest. (2) RD children were not inferior toreading-age (RA) controls. (3) A subgroup of RDchildren with evidence of temporal deficitswere no less proficient on later phonologicalor reading measures than RD children with noevidence of early temporal impairment. (4)Although there was a reliable concurrentcorrelation between temporal deficits andphonological awareness at school entry(suggesting a possible common causeexplanation), early temporal deficits did notpredict later phonological impairment,pseudoword processing difficulties, or specificreading disability. On the other hand, earlytemporal deficits did predict later oralreceptive vocabulary and reading comprehensionweaknesses. These findings suggest thatauditory temporal deficits in dyslexics may beassociated with the same dysphasic-typesymptoms observed by Tallal and her colleaguesin specific language-impaired populations, butdo not cause the core phonological deficitsthat characterize dyslexic groups.