Which study design did Klinberg et al (2005) use to investigate WM training in children with ADHD?

• A. Case series
• B. Randomized controlled trial
• C. Cross-sectional survey
• D. Case-control study

Answer: (B)

This item tests how researchers determine whether an intervention truly causes a change. A randomized controlled trial is the design that best answers that question because participants are randomly assigned to receive the working memory training or to a comparison condition, and outcomes are measured before and after. Random assignment helps ensure the groups are similar at the start, so any differences after training are more likely due to the intervention itself rather than preexisting differences. The comparison group provides a clear baseline to determine the size and significance of any training effect, helping to rule out improvements from maturation, practice, or placebo.

Other designs don’t offer the same level of causal inference. A case series has no control group to compare outcomes against, so it can describe what happened but not whether the training caused it. A cross-sectional survey captures a single time point and can’t show changes over time or relate them to an intervention. A case-control study compares existing groups but isn’t randomized to receive the training and cannot establish causality as cleanly as a prospective randomized trial.

So, for assessing whether working memory training has a causal effect in children with ADHD, a randomized controlled trial is the most appropriate design.