When I was in school, teachers often implored us to not put off studying to the last minute. Sometimes they even suggested that we spread out our studying over a period of weeks. But who has time for that? Most of us just studied the night before the test — with varying results, of course.

But surely research has been done on the ideal way to study. Is it possible to over-study? How much studying is enough? Wray Herbert has uncovered some real data on the problem, from a study by Doug Rohrer and Harold Paschler:

They had two groups of students study new vocabulary in different ways. One group drilled themselves five times; these students got a perfect score no more than once. The others kept drilling, for a total of ten trials; with this extra effort, the students had at least three perfect run-throughs. Then the psychologists quizzed all the students, once one week later and again three weeks after that.

After a week, the students who had done the most studying scored higher, but the advantage disappeared after three weeks. So cramming a whole lot right before the exam might help, but not if you study too early. But what if you take a study break? Rohrer and Pashler repeated the study with breaks varying from 5 minutes to a month. Here’s what they found:

Those who had taken a one-day break performed best when they were tested ten days later. But if they were tested six months later (the laboratory equivalent of long-term learning), the optimal break time was a full month. In other words, as reported in the August issue of Current Directions in Psychological Science, “massing” all the study on a single topic together diminishes learning. It’s better to leave it alone for a while and then return to it, and indeed the longer you want new learning to endure, the longer the optimal break between study sessions.

I wonder if this effect would be maintained over *really* long time periods: If I returned to studying Italian after 19 years since college, maybe I’d be a true master! Actually I tried that a couple years ago before I visited Italy. I’m pretty sure my mastery of the language didn’t equal the level I was at in college, but I was surprised at how much I did remember.

Wray says Rohrer and Pashler’s results even extend beyond memorization and into abstract learning like mathematics. Sounds like their advice isn’t much different from what my teachers told me all those years ago. Now if only a researcher could explain how to get kids to *listen* to their teachers’ advice!