25 Mar 2019

48 Hours

Submitted by Shirley Lin, United States Naval Academy

I like BITeS posts with intriguing titles. Perhaps this one prompts you to wonder if this is a reference to the Nick Nolte/Eddie Murphy movie or the CBS news program or the 1977 song by The Clash. Actually 48 hours is a key result from our next spotlight article, ”Decay of Student Knowledge in Chemistry, ” from Journal of Chemical Education 2011, 88, 1231-1237.

While many of us practicing chemistry educators may have anecdotes about how our students seem to forget course material immediately after an exam or quiz, our colleagues in chemistry education research have designed and executed an elegant experiment in a real-life classroom situation to measure the amount of time required before decay of knowledge was observed. Prof. Diane Bunce, with collaborators from Catholic University of America and Grand Valley State University, gave 230 nonscience majors in a general chemistry course a question on a test that was repeated on a quiz administered 2 to 17 days later. The results revealed a decrease in the mean score of 14% after only 2 days, suggesting that for this population, decay of knowledge occurred in as little as 48 hours.

The factors that go into student learning and achievement are myriad and very complex. To address the possibility the decay occurred because of lack of motivation, the investigators examined the self-efficacy and motivation of students as captured by the course evaluation. They concluded that the decrease in testing performance was not easily explained by lack of motivation as the responses indicated both high self-efficacy and motivation.

These results may be discouraging to teachers but the article also offers suggestions for improving retention of learning. Repeated testing and the use of a spiral curriculum to reinforce concepts throughout the semester can minimize decay of knowledge as observed in student populations enrolled in a high school honors course or an undergraduate nursing chemistry class. Perhaps the next time we give an exam, we follow it up with a short extra-credit review assignment within 48 hours.

Wait….is this a VIPEr challenge? Not an official one. But, Friends of VIPEr, if you try something like this, please post a comment here and let us know how it went!

This BITeS post is dedicated to Prof. Diane M. Bunce, the recipient of the 2019 ACS Award for Achievement in Research for the Teaching & Learning of Chemistry. Prof. Bunce will be delivering her awards address on Tuesday, April 2 at 3:55 PM in the Orange County Convention Center, room W312A.



I wonder if the decay in knowledge could be fit to first order kinetics?  That could be a problem to hand over to the students.

I tried something two years ago in which I gave my inorganic students blank copies of the exam as they left the room.  They were then required to work in groups of three to hand in another completed version of the exm a few days later.  I think it helps students to get to work on the problems immediately afterwards.  I graded the group exams at the same time as I graded all the exams, and then students got something like 90% of their score from their own test and 10% from the group test.  It was a nice way to make sure that students had reviewed the exam material.

Thanks for the highlight, in time for the ACS meeting and the symposium honoring Diane.