Reading difficulties observed in children with Attention Deficit Hyperactivity Disorder (ADHD) may result from deficits in working memory, states a new study by researchers at the University of Central Florida. ADHD is a common childhood disorder marked by impulsive behaviour and an inability to concentrate.
The 2017 study examined schoolboys with ADHD and linked poor reading skills to slow orthographic conversion. Orthographic conversion occurs when we change text into a sound-based code in the brain. Our working memory temporarily stores the code while we process and digest the information. According to the study, slow orthographic conversion leads to poor reading skills.
Badley’s Working Memory Model
Researchers based their investigation on the work of British psychologist, Alan Baddeley. Baddeley created the original working memory model in the 1970s. The working memory model proposes that temporary storage units manage different sensory information in the brain. Sensory information, such as sounds and visual information enters the working memory model administered by the central executive system. The central executive decides how and what to process. The central executive then forwards the important information to long-term memory. The central executive also retrieves relevant information from long-term memory when needed.
According to Badley, sensory information enters working memory and is managed by the central executive function.
The Phonological Loop
According to Baddeley, reading comprehension occurs because the phonological loop, a temporary storage unit, coordinates with the central executive. Together, the two systems convert phonological information into something meaningful. Phonological information consists of sounds and words, including what we read.
The phonological loop temporarily houses phonological information. The central executive then connects the information with previously stored information in long-term memory. The process sifts information and keeps related data in the working memory. Reading and conversations make sense because of the interrelated processes.
According to Badley, auditory information is temporarily stored in the phonological loop before further processing.
Findings of the Study
The study examined thirty-one ADHD diagnosed and thirty normally developing boys aged eight to twelve years of age. All boys completed orthographic conversion tasks over four consecutive test sessions. Orthographic conversion tasks assess reading comprehension and recall abilities. Results indicated poor orthographic conversion in boys diagnosed with ADHD.
Researchers concluded that the poor test results of the ADHD group indicate deficiencies in both executive function and the phonological loop. Deficiencies may arise from a bottleneck entering the phonological loop. The bottleneck subsequently increases demands on the central executive. Reading comprehension and recall abilities may suffer as a result.
Baddeley, A. (1996). The fractionation of working memory. Proceedings of the National Academy of Sciences of the United States of America, 93(24), 13468–13472. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC33632/pdf/pq013468.pdf
Friedman, L.M., Rapport, M.D., Raiker, J.S., Orban, S.A., & Eckrich, S.J. (2017). Reading comprehension in boys with ADHD: the mediating roles of working memory and orthographic conversion. Journal of Abnormal Child Psychology. 45(2). 273-287. https://doi-org.myaccess.library.utoronto.ca/10.1007/s10802-016-0171-7