Grade inflation and the Dunning-Kruger effect


Jason Collins


January 21, 2015

The famous Dunning-Kruger effect, in the words of Dunning and Kruger, is a bias where:

People tend to hold overly favorable views of their abilities in many social and intellectual domains

in part, because:

[P]eople who are unskilled in these domains suffer a dual burden: Not only do these people reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the metacognitive ability to realize it.

There have been plenty of critiques and explanations over the years, including an article by Marian Krajc and Andreas Ortmann who argue the overestimation of ability is partly a signal extraction problem. In environments where people are not provided with feedback on their relative standing, they are will tend to make larger estimation errors.

Krajc and Ortmann point out that the Dunning-Kruger study, as is typical, was done using psychology undergraduates at Cornell. This sample is already a self-selected pool that excludes those unable to gain admission. And once in University, the feedback they receive on their performance is not as useful as it could be. Krajc and Ortmann write [references largely excluded]:

In addition, it is well-known from studies of grade inflation that grades at the undergraduate level have – with the notable exception of the natural sciences – become less and less differentiating over the years: more and more students are awarded top grades. For example, between 1965 and 2000 the number of A’s awarded to Cornell students has more than doubled in percentage while the percentage of grades in the B, C, D and F ranges has consequently dropped (in 1965, 17.5% of grades were A’s, while in 2000, 40% were A’s). These data strongly suggest that Cornell University experiences the same phenomenon of (differential) grade inflation that Harvard experiences and the schools discussed in Sabot and Wakeman-Linn (1991). The dramatic grade inflation documented for the humanities and social-sciences devalues grades as meaningful signals specifically in cohorts of students that are newly constituted and typically draw on the top of high-school classes. Inflated grades complicate the inference problem of student subjects that, quite likely, were students in their first year or in their first semester.

Grade inflation is robbing people of feedback they could use to understand their level of competence.

*A post by Eaon Pritchard on the “Dunning-Kruger peak” reminded me that I was sitting on this passage.