Reaction Time and Fine Motor Dexterity in Adults With Intellectual Disabilities

PURPOSE: The primary purpose of this study was to examine the relationship between reaction time and fine motor dexterity in a sample of adults with intellectual disabilities. A secondary purpose was to compare individuals with intellectual disabilities with individuals with Down syndrome, a subgroup of individuals with intellectual disability who have noted motor skill delays.

BACKGROUND: Many fine motor tasks are completed quickly and with precision. Individuals with intellectual disabilities, including those with Down syndrome, have been shown to have decreased reaction times and poor fine motor dexterity compared with typically developing peers. Poor reaction time and fine motor dexterity might be related to atypical information processing in the central nervous system or altered function in the prefrontal cortex area and cerebellum during tasks. As a result of this lack of fine motor dexterity, self-care tasks, such as using a toothbrush or knife and dressing, may be difficult for this population.

DESIGN: This descriptive, comparative study included 32 participants (14 female, 18 male) with intellectual disabilities (age range = 18–50 yr; M age = 28.5, SD = 8.96) recruited during a statewide Special Olympics event. Of the 32 participants, 11 had Down syndrome.

METHOD: Following a familiarization process, two trials were administered to each participant for each test for both reaction and fine motor dexterity. Reaction time was assessed using a Newtest Reaction Time Scale under a simple condition in which the seated participant pressed a button when they heard a beep and saw a light. Participants completed two trials with each hand. Fine motor dexterity was completed using the Purdue pegboard test. Participants completed two trials for all three subtests (dominant hand, nondominant hand, and bimanual). The assembly task was omitted.

The participants’ average reaction time scores and one-trial and sum-of-three-trials scores for each of the three Purdue pegboard subtests were analyzed using Pearson product–moment correlations, and independent-samples t tests were used to look for differences between genders and between individuals with intellectual disability and those with Down syndrome. Cohen’s d effect sizes were calculated to quantify the size of the difference between groups.

RESULTS: There were moderate to strong statistically significant correlations (–0.50 to –0.70, p < .05) between reaction time and each subtest of the Purdue pegboard test. Reaction times for the nondominant hand had stronger correlation values for all three Pegboard subtests. Participants with Down syndrome did not perform as well as their peers with intellectual disabilities. Although the two groups were not significantly different on any task, there were consistently medium effects sizes between the two groups (0.48–1.01). There was no relationship between age and reaction time (r = –.03, p = .85).

CONCLUSION: Results of this study suggest there is a relationship between reaction time and fine motor dexterity in adults with intellectual disabilities. These results might also help explain why some individuals with intellectual disabilities perform poorly on fine motor dexterity tasks. Future research should increase fine motor task complexity to better understand the role of motor planning or information processing. These results add to the body of literature related to poor reaction time and fine motor skills found in individuals with intellectual disabilities.

IMPACT STATEMENT: Studying the relationship between reaction time and fine motor dexterity in individuals with intellectual disabilities may be beneficial for identifying the exact mechanism in the brain impacting these delays. It may also allow occupational therapists to better tailor therapies. Teaching new strategies for fine motor tasks, conditioning and strengthening cues, and identifying hand preferences for various tasks requiring quick, precise movements are potential ideas for improving function in both these areas. By improving functioning in these areas, individuals with intellectual disabilities might be able to improve their speed, accuracy, and precision and be more successful in completing activities of daily living.

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