Effect of Massed Versus Interleaved Teaching Method on Performance of Students in Radiology

Radiology instruction is based on the principle that grouped (or massed) repetition of an intellectual activity leads to expertise. The aim of this study was to test the hypothesis that the spaced (or interleaved) method of teaching chest x-ray interpretation is more effective than the massed method.

After institutional review board approval was obtained, 40 first- and second-year medical students were randomized into two groups matched by age, gender, and education experience. Both groups saw six examples of 12 common chest radiographic patterns, one grouped, the other scrambled randomly without repeating strings. After a distraction, participants took a multiple-choice test consisting of two cases in each radiographic pattern, one previously shown, one new. Results were analyzed using two-tailed Student's t test of proportion.

Comparing interleaved and massed groups, the average overall score was 57% versus 43% (P = .03), the recollection score was 61% versus 47% (P = .03), and the induction score was 53% versus 40% (P = 0.10), respectively. Comparing second- and first-year students, average scores were 67% and 39%, respectively (P < .01). First-year students in the interleaved and massed groups scored 55% and 36% (P = .02) in recall and 40% and 28% (P = .10) in induction. Second-year students in the interleaved and massed groups scored 71% and 63% (P = .36) in recall and 74% and 59% (P = .03) in induction.

The interleaved method of instruction leads to better results than the massed method across all levels of education. A higher level of medical education improves performance independent of method of instruction.