Skills to Develop

### Research conducted by

Pearson et al. (2003, see reference below)

### Case study prepared by

David Lane and Emily Zitek

### Overview

This study investigated the cognitive effects of stimulant medication in children with mental retardation and Attention-Deficit/Hyperactivity Disorder. This case study shows the data for the Delay of Gratification (DOG) task. Children were given various dosages of a drug, methylphenidate (MPH) and then completed this task as part of a larger battery of tests. The order of doses was counterbalanced so that each dose appeared equally often in each position. For example, six children received the lowest dose first, six received it second, etc. The children were on each dose one week before testing.

This task, adapted from the preschool delay task of the Gordon Diagnostic System (Gordon, 1983), measures the ability to suppress or delay impulsive behavioral responses. Children were told that a star would appear on the computer screen if they waited “long enough” to press a response key. If a child responded sooner in less than four seconds after their previous response, they did not earn a star, and the 4-second counter restarted. The DOG differentiates children with and without ADHD of normal intelligence (e.g., Mayes et al., 2001), and is sensitive to MPH treatment in these children (Hall & Kataria, 1992).

Does higher dosage lead to higher cognitive performance (measured by the number of correct responses to the DOG task)?

### Design Issues

This is a repeated-measures design because each participant performed the task after each dosage.

### Descriptions of Variables

Table $$\PageIndex{1}$$: Description of Variables

 Variable Description d0 Number of correct responses after taking a placebo d15 Number of correct responses after taking .15 mg/kg of the drug d30 Number of correct responses after taking .30 mg/kg of the drug d60 Number of correct responses after taking .60 mg/kg of the drug