Although collaborative learning is becoming a widely popular instructional method, little research has been undertaken considering human cognitive structures and their influence on the design of collaborative learning tasks. Using cognitive load theory as a theoretical framework in this study, forty-five undergraduate students were assigned to either individual or two-person groups to solve simple and complex tasks. Overall, we found that participants took less time, scored better, and invested less cognitive effort while solving simple tasks compared to complex tasks, which indicates complex tasks were more cognitively demanding and difficult to solve. Consistent with cognitive load theory, groups scored higher than individuals while solving complex tasks. Analysis of nine semi-structured interviews on group participants revealed that collaborative interactions play an important role in the problem-solving process and resulted in three main themes that included: (1) perceived benefits, (2) associated challenges, and (3) various strategies used for collaborative problem-solving processes. These findings suggest that collaborative learning can overcome individual working memory limitations through the collective working memory effect, and collaborative interactions are vital in the groups' problem-solving processes. Based on the study findings, we discuss the significance of the study and provide implications for research and practice as well as study limitations.