In one sentence
Seventh-grade math students often liked spaced practice but nearly half failed to see it as effective — while interleaved (mixed) practice was judged both unlikable and ineffective by most, despite strong evidence for both strategies.
What the researchers did
Hartwig and Rohrer surveyed grade 7 math students about two high-utility strategies: spaced practice (same kind of problems spread across sessions) and interleaved practice (different problem kinds mixed rather than blocked).
Study 1 asked 174 students about the efficacy and likability of spacing and interleaving. Study 2 focused more deeply on interleaving with 233 grade 7 students, comparing perceptions of interleaved versus blocked practice on effectiveness, preference, time cost, and difficulty.
What they found
- In Study 1, spaced practice was often judged likable, but nearly half of students failed to recognise its efficacy.
- Interleaved practice was judged both unlikable and inefficacious by most students in Study 1.
- In Study 2, students again erroneously judged interleaved practice to have low efficacy.
- Versus blocked practice, interleaved practice was judged less effective, less preferable, more time-consuming, and more difficult.
- Perceptions differed by strategy: spacing had a likability–efficacy gap; interleaving was disliked and mistrusted.
What this means for learners and educators
- Do not assume students will adopt spacing or mixing because the evidence is strong — beliefs and feelings may block use.
- Teach why a mixed set that feels worse can transfer better on unsorted tests; pair explanation with a short delayed quiz that shows the gap.
- Treat “this feels hard / slow” as expected for interleaving, not as proof the method failed.
- Motivation design may need different levers for spacing (raise perceived efficacy) versus interleaving (raise both liking and trust).
Limitations and what we don't know yet
These are perception surveys, not experiments that change practice and remeasure grades. Samples are grade 7 math in the authors’ setting — other ages and subjects may differ. The paper identifies barriers; it does not yet test which classroom messages best flip those beliefs. Knowing students dislike interleaving does not tell us how large the learning cost of avoiding it is in their specific courses.