Which of the following outcomes showed significant improvement as a result of the WM training?

• A. Sensory perception
• B. Reaction time only in a motor task
• C. Sleep quality
• D. Working memory capacity

Answer: (D)

Working memory training is meant to boost the ability to hold and manipulate information in the mind over short periods. The most direct and reliable sign of improvement is increased working memory capacity—being able to handle more items or perform mental operations more efficiently on WM tasks (like higher spans or quicker updating). That’s why this outcome is the best choice: it reflects the core skill the training is designed to enhance.

Other areas—sensory perception, motor-task reaction time, and sleep quality—are governed by different systems. WM training targets cognitive control and temporary storage, so these domains aren’t consistently or robustly affected, which is why they’re not the expected significant outcomes.