Length of Testing: The Paradox

As McGill University Psychology students, most of us have participated in psychological tests, whether the motivation was sheer interest or to gain extra credit for certain classes (usually the latter). In my personal experience with psychological tests, they all share one common feature: they’re exhausting! To give one example, I have sat in a chair in a laboratory listening to and trying to decipher between different bird chirping sounds for nearly 2 hours, with very little break. About an hour in, my willpower had been depleted and the rest of the test felt like guesswork. One might ask: How can one expect to get reliable numbers on psychological tests when we’re working our participants to the point of cognitive fatigue? Let’s explore this further.

One response that you might not expect is that the reverse may be true. Could it really be that we are performing the same or even better on tests that are longer and more tiring? A 2009 article by Ackerman and Kanfer suggests that this may be the case. A large cohort of 239 University students participated in and completed 3 tests of different lengths. While subjective fatigue was greater as a result of the longer tests, performance actually “increased in the longer test length conditions, compared with the shorter test length condition” (Ackerman and Kanfer, 2009). A corroborating article was published in 2013 by Jensen, Berry and Kummer, in which the effect of exam length and cognitive fatigue on performance was measured. It was concluded that lengthier testing led to greater performance and that lengthier exams “did not result in lower performance due to fatiguing conditions” (Jensen, Berry and Kummer, 2013).

What are the ramifications of such findings? Well it could mean two things. First, it suggests that experimenters shouldn’t worry about their tests tiring people to mental exhaustion, because even if the participants report fatigue, research shows that it will not affect their performance. However, it also means that further research is required on the mechanisms of fatigue in relation to testing. Since we do not know that these effects described above relate to all forms of psychological tests, it might be prudent for psychological researchers to create longer and shorter versions of their tests to control for the effects of fatigue.

Does this mean that we should all go into our exams without sleeping the night before? Certainly not. The effects of increased performance could be due to third variable effects, such as the greater sample of questions and measures on these lengthy tests. Whatever the reason, what we see here is a phenomenon that we are so accustomed to in psychology: complex answers to simple questions.


Ackerman PL, Kanfer R. Test length and cognitive fatigue: an empirical examination of effects on performance and test-taker reactions. J Exp Psychol Appl. 2009 Jun;15(2):163–81.

Jensen J, Berry D, Kummer T. Investigating the Effects of Exam Length on Performance and Cognitive Fatigue. PLOS. 2013 10.1371/journal.pone.0070270.

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