Homework SourseThis study investigated the cognitive effects of stimulant m
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).
Design Issues
This is a repeated-measures design because each participant performed the task after each dosage.
Descriptions of Variables
What is the independent variable of this experiment? How many levels does it have?
What is the dependent variable? On what scale (nominal, ordinal, interval, ratio) was it measured?
| 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 |
Solution
What is the independent variable of this experiment? How many levels does it have?
Independent variable: Amount of drug taken
Levels: 4 levels
**********************************
What is the dependent variable? On what scale (nominal, ordinal, interval, ratio) was it measured?
Dependent variable: Correct Delay of Gratification Responses
It is measured in RATIO, as they count the number of correct responses, which has a minimum value of 0. [ANSWER]
