During a recent study, researchers found that students who studied in groups performed better on tests compared to those who studied alone. The researchers concluded that group study enhances learning and improves academic performance.
However, the researchers did not consider whether the students who studied in groups were inherently more motivated than those who did not, nor did they explore the possibility that group dynamics could lead to distractions.
Which of the following, if true, would most strengthen the researchers' conclusion that group study leads to improved academic performance?