Time Between Tests

(Photo: Eric E Castro)

A new working paper (abstract; PDF) by Ian Fillmore and Devin G. Pope examines whether “cognitive fatigue” has any impact on exam results. The researchers looked at the number of days students had between AP exams, and found that resting time matters:

In many education and work environments, economic agents must perform several mental tasks in a short period of time. As with physical fatigue, it is likely that cognitive fatigue can occur and affect performance if a series of mental tasks are scheduled close together. In this paper, we identify the impact of time between cognitive tasks on performance in a particular context: the taking of Advanced Placement (AP) exams by high-school students. We exploit the fact that AP exam dates change from year to year, so that students who take two subject exams in one year may have a different number of days between the exams than students who take the same two exams in a different year. We find strong evidence that a shorter amount of time between exams is associated with lower scores, particularly on the second exam. Our estimates suggest that students who take exams with 10 days of separation are 8% more likely to pass both exams than students who take the same two exams with only 1 day of separation.

The race effects are particularly interesting:

Relative to the omitted category (White students), Black and Hispanic students benefit less from a greater number of days between exams. Asian students benefit even more than White students from a greater number of days between exams. The reason behind these heterogeneous effects is unclear and our data do not allow us to distinguish among various explanations. One possible scenario is that certain groups of students simply don’t recover their mental acuity as fast or they get stressed or “burned out” quicker than other groups. Another, perhaps more plausible, mechanism is that the students with larger effect sizes (e.g. females, Asians) study more for AP exams than their counterparts and thus have a higher value of having extra days between exams so as to have more time to “cram” for the second exam.


As the "more plausible" scenario highlights, it seems like they'd have trouble distinguishing "cognitive fatigue" from "proper time management". In college, a lot of students put off studying for the second exam until the first one is done because the first one seems more "pressing". Spacing tests out forces a more even distribution of studying across subjects, especially given that the second tests scheduled for the same day doesn't typically prompt students to start studying twice as far in advance.

I'm not usually a fan of "people aren't fully rational" explanations, but this one is a recurring personal theme.


Seems weird to blame "cognitive fatigue," as if the students are just relaxing their minds in between exams. From my experience as a student I'd say that the additional study time to devote to each specific exam is more likely to be causing the improved performance. Either way, interesting research to quantify the effect, and nice work discovering the "natural experiment" that allowed them to make the measurement!

science mindful

In real science' there is no proper time management. Ideas come when they please and not necessarily when it pleases us. I was fortunate to have had teachers who understood my objective.


A somewhat less exotic of an explanation is suggested in the second paragraph describing the race effects. Instead of saying that there is an ephemeral difference in how quickly different races recover from cognitive fatigue, it seems a lot more likely that the difference is due to different amounts of studying.

This seems to be easily explained that different groups put in more study between tests. Especially given humanity's tendency toward procrastination.

If group (regimented) R and (procrastinator) P only have 1 day of study time, the functional difference in actual studying done is going to be limited. "R" puts in 6 hours of study while "P" puts in 5. (out of the air example numbers) The difference in scores is going to be minimal, just based on the difference in studying.

But, if there are 10 days, regimented R can put in 10 days of 3 hours each and wind up with 30 hours of study. Procrastinator P, though, puts in 0, 0, 0, 1, 1, 2, 2, 3, 4, 6 hours of study: 19 hours.

There will be significant differences between test results. Tests with short times between them will have small differences in outcomes for the two groups while tests with longer times between them will have greater differences.

Are there any studies out there that show the recovery time for a person's mental acumen? Does a high-demand effort like a AP test take a day to recover? Two days? Three days? A week?



Would be nice if were only fatigue. You have forgotten need for calm n the face of unforseen developments over which one has no control and feels helpless. Knowing tragedy.... does romney have any such knowledge. If you really believe you are responsible for your fate then you wont and have no real feeling for others.



Or ability to understand others 'diiferent' !


What is wrong w saying i do not know? On a test.' There are some who may think it a sign of weakness. But the rush to judge in the absence of or before knowing all the facts as we have learned from mit can be disastrous.

Russell Harris

First-year engineering (freshman) was 13 exams in 10 days ... but we were all in the same boat. The experience whittled 410 students down to about 220.

In case you're wondering, about 150 of us graduated 4 years later - the first cut was the deepest.


It seems like the mental fatigue theory is totally unnecessary when the much simpler option of "more time to study" exists. If anything, the magnified difference in groups that are stereotypically more studious corroborates this.



They don't have more time to study necessarily. If the 2 tests are on the same day they can still study a lot before the two tests. If the tests aren't on the same day they can spread out there study (so as not to get fatigued).

Enter your name...

The experiment doesn't seem to address other sources of cognitive fatigue, which are unlikely to be identical between all groups. AP exams happen at the same time as major papers and final exams for a lot of schools. Also, cognitive fatigue isn't exclusively an academic phenomenon. "What will I wear to the prom?" or "How do I deal with my chaotic family situation today?" can also drain that resource. I'd be interested in seeing a breakdown by day of the week.

Sophie Russell

From my experience as a student it isn't just a time-management issue - I used to love it when I had a three day or more gap between exams because I found it much easier to focus my mind on a single subject at any one time, forgetting absolutely everything else. This was a perfectly rational decision made as soon as I found out exam dates. With a focused mind I always performed better than when I had revised for two exams simultaneously.

But I forgot everything I learnt for each exam within about a week because I focused solely on short-term memory, leaving me with first class honours but no knowledge of economics - so perhaps we should encourage exams closer together?


Mit seemed stressed. I can relate. Was not an easy test. I wish they both would have answered that what if question. Neither did. So i fella sleep.


...another instance of economists highlighting some phenomena that other fields have already investigated for years.


It seemed odd to me that m would repeat o on foreign policy and then i got it. The rrpublican strategy....promise everything o gave. then focus on economics sounds almost like divide and conquerish.


Spaced-out exams do help with memory performance. It allows us to practice retrieving info. What we cannot recall signals what we need to review.