Brigham and Women's Hospital Conducted a Study with Two Groups

Brigham and Women's Hospital conducted a study with two groups of participants.One group was allowed to experience deep sleep, while the other group was deprived of deep sleep.Next, participants in both groups completed a visual task.Results indicated that performance did improve on the visual task for participants in the group that experienced deep sleep.In this study, what was the independent variable?

A) the conditions of sleep
B) performance on visual spatial task
C) percent correct on visual spatial task
D) reaction time on visual spatial task