The concept of 'cognitive load' refers to the total amount of mental effort being used in the working memory. In educational settings, instructional designers often aim to manage cognitive load to optimize learning. According to Sweller's cognitive load theory, learning is hampered when the intrinsic load (complexity of the material) and extraneous load (how the material is presented) exceed the learner's working memory capacity. However, recent research suggests that a certain degree of desirable difficulty, such as interleaving practice or introducing spaced repetition, can actually enhance long-term retention, even though it may temporarily increase cognitive load. This paradox implies that the optimal level of mental effort is not always the lowest, but rather a balance that challenges learners without overwhelming them.