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It's that time of year again: Final exams. Are you taking (or giving) a cumulative final exam? From a cognitive psychologist's perspective, you should be: Cumulative finals may not be fun, but they can significantly enhance long-term learning. [edit: removed this link]
The spacing effect
Cumulative exams take advantage of the spacing effect: If you have already studied something, studying it again after a delay can produce a huge amount of learning. (Studying the same information without letting time pass in between produces much less learning.) A cumulative exam means that in December you're going to have to restudy whatever you learned back in September. Because that involves spacing, you're going to learn a lot from doing it.
Spaced learning is especially important for long-term learning. If you want to remember something for the short term, maybe just for your exam in a few days, spaced learning will help some. If you want to learn something for life, spaced learning is absolutely crucial. Research shows that the longer you want to remember something, the more you should space your learning. (This article reviews research on spacing effects in education.)
Repetition
When scientists study spaced learning, they hold the number of times you'll study constant. But a cumulative exam actually makes you spend additional time studying material from earlier in the year. Studying more obviously helps, and some studies show that it particularly helps in the long term (particularly if the studying involves self-testing). Thus, cumulative exams offer the advantages spaced repetitions and more repetitions.
Expectations
Knowing there will be a cumulative final probably changes the way most people study (for the better). But what if students weren't allowed to study differently? Here's a study that suggests that simply telling students that there will be a cumulative final may enhance their learning. The data were collected in a situation that was, admittedly, far from a real classroom experience. But the findings suggest that how we process and store knowledge depends on how long we expect to need to know it. The effect would probably have been amplified if the experimenters had allowed their subjects to change their behavior based on their expectations, which is what happens in real life.
Don't let your intuition fool you
We all know that studying more is good, right? Well, yes. But it turns out that people often underestimate the value of repeated studying. There seem to be at least three reasons for this misperception.
First, people don't recognize the benefits of spacing (they often think it has negative effects). Second, people are biased to think their memories won't change much in the future--so they underestimate the benefits of future studying. And third, people think that once they can recall something, they know it. And maybe they do in the short term, but just because you can recall it now, that doesn't mean you won't have forgotten it later. Thus, people think studying something they "know" is a waste of time, when in reality studying it more (or, actually, testing themselves on it) can have enormous long-term value.
Improving Education
In a perfect world, Bio 101 students would have to take a cumulative Bio 101 exams a year after completing the course. There'd be two advantages of doing so: The first is that even small amounts of spaced study can produce long-lasting learning. Second, if teachers geared their teaching toward longer-term learning, they might do things differently in ways that would make education more effective.
Update 2019
I wrote this blog in 2010. New research has come out since then. I'd especially like to highlight three studies that took place in real classrooms: One is titled Short- and Long-Term Effects of Cumulative Finals on Student Learning, another is called Cumulative Exams in the Introductory Psychology Course, and the third is The Effect of a Final Exam on Long-Term Retention.
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