A very sophisticated and comprehensive set of 12 experiments confirms what experienced teachers have long known: students over-estimate how much they know and under-estimate the value of repeated study of the same material. This bias may apply to everyone, but the study was performed on college students. UCLA researchers studied the reliability of people's ability to judge how well they had remembered something just studied and to predict how well they could remember if they went over the same material in several sessions.

They asked the students to look at a list of word pairs and make two estimates: one a judgement of how well they remembered what they just studied and the other a prediction of how well they would be able to remember the words after subsequent study of those same word lists.

When asked after a given study trial to judge how well they thought they remembered, students' judgment of their knowledge was not confirmed by actual performance on the test.That is, they over-estimated how much they had learned.

Amazingly, students predicted little or no learning improvement would occur with repeated study sessions, yet they actually showed large increases in actual learning with repeated study. The change in predicted performance was about the same, irrespective of whether the word pairs were deemed easy or hard to remember. However, the actual performance benefit of extra study was especially marked for the hard-to-remember words.

Other studies have shown that people fail to predict accurately how much their memory of specific learning will deteriorate over time after the intiial learning.

Why does this matter? Well, it affects how well one manages learning tasks; that is, choosing the best activities that will create lasting memories, as for example, students choosing how and when to study. The implication is that students don't study as much as they should because they don't appreciate the value of extra study, especially for hard-to-learn material. They also don't study as much as they need to because they think they have learned more than they really have.

Is the problem that students are generally not as smart as they think they are? Or do they fail to study more because they don't correctly realize how much it would help? The ultimate consequence is that students tend to study too little and give up too quickly.

The authors suggest that these inaccurate beliefs and the negative consequences just reflect normal psychology. They do not consider that mental laziness could be a factor. Nor do they consider that this effect might be age-specific.

This may also relate to an observation that has puzzled me ever since I wrote my original book on memory improvement. Students have not been as interested in what the book had to say as I expected. Nor do they show as much interest as I anticipated in attending my lectures on the subject. At one unversity where I recently gave a well-advertised talk on how to improve memory, not one student showed up -- only faculty. Older adults, in general, seem to realize they need to work on their memory. Students tend to think they are either just fine as they are or can't improve.

A related matter is that students don't appreciate the value of testing in enhancing memory. This value was confirmed in the present study, and I have elsewhere discussed similar findings. Testing forces retrieval of stored information and that retrieval is a strong rehearsal process that reinforces the memory.


Kornell, N. and Bjork, R. A. 2009. A stability bias in human memory: overestimating remembering and underestimating learning. J. Exp. Psychol. 138 (4): 449-468.

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