Why interleaving feels harder and less effective
When learners practice one type of problem or skill repeatedly—blocked practice—they get into a rhythm. In a French grammar study, the blocked group used the new structure with greater fluency, showing fewer mid-clause pauses during training and at posttest [2]. That smoothness is a real experience, but it reflects immediate ease, not durable learning. Interleaved practice, which mixes different types of problems or concepts, forces the learner to switch and adjust constantly, so it feels more effortful. Nursing students who practiced auscultation with interleaving found it more effortful than blocking [5].
This effort is not a sign of failure. In the same grammar study, the interleaved group was more accurate in using the structure, though at the expense of fluency [2]. The discomfort of switching is part of what makes interleaving work: it pushes learners to notice differences between problem types and to select the right strategy each time, rather than falling into an automatic routine.
What learners miss when they judge by feel
Learners tend to use their moment-to-moment experience as a gauge of learning. If practice feels easy and fluent, they assume they are learning well; if it feels choppy and hard, they assume it is not working. In the auscultation study, many students were unaware of the learning benefits of interleaved practice even after experiencing it [5]. Their judgment was based on how the practice felt, not on how much they actually learned.
This misjudgment is not limited to one subject. In a classroom study with high-school science students, interleaved quizzes led to better performance a month later than blocked quizzes—63% correct versus 54% [1]. Yet the abstract does not report whether students noticed this difference. The evidence from the nursing study suggests that even when interleaving works, learners may not recognize it [5].
When interleaving helps most—and when it might not
Interleaving is not a universal fix. In a study with German third-graders learning subtraction strategies, interleaved practice with comparison prompts helped students adapt their strategy use, but the benefits depended on the learner. Students with higher need for cognition—a tendency to enjoy effortful thinking—benefited more from interleaving, while prior knowledge helped more in the blocked condition [3]. So for some learners, especially those who find cognitive effort less rewarding, the harder feel of interleaving may be a real obstacle, not just a misperception.
The type of task also matters. In the grammar study, interleaving improved accuracy but slowed down production [2]. In auscultation training, interleaving improved diagnostic accuracy [5]. In science quizzes, interleaving boosted later test scores [1]. These are different outcomes—accuracy, fluency, diagnostic skill—and interleaving does not improve all of them equally. A learner who values speed or smooth performance might reasonably prefer blocking, even if it produces weaker long-term retention.
How learners can judge practice more accurately
The practical fix is to stop relying on how practice feels and start checking what it produces. Since interleaving often feels worse but works better, learners can use delayed tests or real-world performance as their guide. In the auscultation study, the benefits of interleaving showed up in test scores, not in students' comfort [5]. In the science classroom, the advantage appeared a month after the quizzes ended [1].
Teachers and trainers can also explain the difference directly. When students understand that effortful switching is a feature of effective practice, not a bug, they may be more willing to stick with it. The grammar study suggests that interleaving promotes accuracy by forcing learners to distinguish between different uses of a structure [2]. The subtraction study suggests that comparison prompts can help, especially for students who might otherwise struggle [3]. But the evidence also shows that not every learner benefits equally, so a one-size-fits-all push toward interleaving may not be wise.
Sources used in this answer
Interleaving Retrieval Practice Promotes Science Learning
Interleaved quizzes led to better long-term test performance than blocked quizzes in high-school science classrooms.
The effects of interleaving and blocking practice on L2 contextualized grammar learning
Interleaved practice improved accuracy in using a French grammatical structure but reduced fluency compared with blocked practice.
The role of prior knowledge and need for cognition for the effectiveness of interleaved and blocked practice
Interleaved practice with comparison prompts supported adaptive strategy use, with benefits varying by students' prior knowledge and need for cognition.
Interleaved practice in multi-dimensional learning tasks: Which dimension should we interleave?
Interleaving learning tasks leads to better learning results than blocked practice, but the dimension on which tasks are interleaved matters.
Improving Diagnostic Accuracy of Lung Auscultation Through Interleaved Practice: A Quasi‐Experimental Field Study
Interleaved practice improved nursing students' auscultation performance, but many students found it more effortful and were unaware of its benefits.