Advances in Cognition, Education, and Deafness

Specialized Cognitive Function Among Deaf Individuals: Implications for Instruction

Specialized Cognitive Function Among Deaf Individuals: Implications for Instruction Helen B. Craig Harold W. Gordon T his study analyzed the preliminary results of an ongoing three-year study of cognitive function and cognitive education among hearing-impaired persons and considers these results in the context of previous studies (Craig & Gordon 1988; McKee 1987). In the earlier studies, the cognitive profile of deaf individuals was found to differ significantly from that of normally hearing persons. Cognitive task performance was below average, as might be expected, for the verbal and sequential skills associated with the left hemisphere, but more importantly, performance was above average for the visual and spatial skills associated with the right hemisphere. In addition, reading and mathematics achievement directly correlated with this cognitive profile, especially with verbosequential performance. In potentially related investigations (Craig 1987; Martin & Jonas 1986), the systematic implementation of a thinking skills program, Feuerstein's Instrumental Enrichment (FIE), has been found significantly to improve reading and mathematics achievement among deaf students. FIE is a metacognitive program that includes a selective focus on several of the visuospatial and verbosequential features associated with specialized cognitive functions. Consideration of the FIE results and of their potential interaction with our findings on brain function formed the basis for the current investigation. The purpose of this project was both theoretical and practical. The theoretical This project is being supported by Grant #H133G80184 from the National Institute on Disability Rehabilitation Research (NIDRR), Office of Special Education and Rehabilitative Services, U.S. Department of Education. 231 232 Neuroscientific Issues goal was to determine whether the pattern of performance of specialized brain functions-the cognitive profile-differs in individuals who have normal vs. impaired hearing. The practical goal was to determine whether the cognitive profile of hearing-impaired students can help to predict which training materials and techniques will most facilitate their academic achievement. The objectives, then, are fourfold. 1. To explore further, in a cohort of congenitally profoundly deaf persons , the relative performance of cognitive functions associated with the left and right hemispheres; 2. To determine whether there exists a "critical period" for development of brain organization and/or a "critical degree of deficit" relating to differing ages of onset and differing degrees of hearing loss; 3. To explore the relationship between cognitive profile and academic achievement; and 4. To determine whether success in a training program in higher-order thinking (such as FIE) can be attributed to the nature of training material that favors specialized brain function-specifically, whether a match or a mismatch between materials and students' cognitive profiles will be most effective for improvement in academic achievement . RATIONALE AND REVIEW OF PREVIOUS STUDIES The main theoretical hypothesis underlying this series of studies was that congenital loss of auditory experience alters the cerebral development and the normal lateralization of specific cognitive tasks associated with brain function, particularly of neurosystems associated with the left cerebral hemisphere. It was further hypothesized that these developmental differences may well be a critical factor influencing the academic achievement of persons with profound and congenital hearing impairment; and, by extension, that intervention techniques that take into consideration the cognitive profile of each deaf student may improve academic achievement. Underlying these hypotheses are two potentially interacting factors: 1. The identification of the left hemisphere as an analytic, serial, timedependent processor, uniquely specialized for speech, writing, and other language skills (Bradshaw & Nettleton 1983); and 2. The observation that children whose hearing is significantly impaired, regardless of preferred communication mode, will miss out on a major portion of the highly sequential and temporal input that is conveyed auditorily. It is also reasonable to suppose that continued deprivation of serial stimuli may further reduce development of these processes in the left hemisphere, whereas increased reliance on visual sources, which are inherently less sequential than the auditory, may potentiate right hemisphere development. Specialized Cognitive Function Among Deaf Individuals 233 METHOD The current study involved two major components, cognitive evaluation and cognitive training, both conducted throughout the three-year period. Evaluation Component Approximately 200 deaf subjects were evaluated over the three years, divided evenly into 4 cells in a 2 x 2 matrix-age of onset (congenital or postlingual) by severity of hearing loss (profound or moderate-to-severe). The age range was 15 to 45 years, with Performance IQs above 80. The major evaluation tool was the Cognitive Laterality Battery (CLB) (Gordon 1986). The CLB is specifically designed to measure the verbosequential...