Imperfect analogies: shortcuts to active learning

Note from Jeremy: this is a guest post from my friend Greg Crowther. Who among other things has been a biochemist, and an instructor in various biology courses including ecology. He’s an unusually thoughtful and creative teacher, for instance using songs to teach anatomy and physiology. Oh, and he has three papers in Annals of Improbable Research (e.g.), which is like the science humor equivalent of having three Nature papers. Thanks to Greg for writing us a guest post on a handy teaching tip. 


Most people who think hard about how to teach well accept that students should engage in “active learning,” which has been defined (by Freeman et al. 2014) as follows: “Active learning engages students in the process of learning through activities and/or discussion in class, as opposed to passively listening to an expert. It emphasizes higher-order thinking and often involves group work.”

Sounds good, right?  In general, it is good.  I enjoy challenging students with hard problems and helping them find their way toward an answer, and they are usually glad to be moving and talking, especially if the problems resemble ones they’ll encounter on tests.

Active learning is relatively easy to include in teaching about a specific research study.  For example, after providing some appropriate context, one can simply work through the figures by asking students how and why the data in each figure were collected and what they mean (Round & Campbell 2013).

When teaching basic conceptual material, though, I slip into straight-up lecture mode more often than I’d like.  It can be very time-consuming to add nontrivial interactivity to coverage of this material.

However, I do have one fall-back strategy for quickly turning a traditional lecture slide into a mini-discussion.  I call this approach the “Dissection of the Imperfect Analogy.”  Here’s how it works.

(1) Describe a scientific concept, relationship, or process that you want students to understand well.

(2) Offer an analogy that may help illuminate the concept, relationship, or process.

(3) Ask students, “In what way(s) is this analogy useful?  In what way(s) is this analogy misleading?” Students discuss with their neighbors before being called upon.

(Optional) Challenge students to come up with a different analogy that overcomes a limitation of the previous analogy.

Why do I like this approach?

(1) It encourages careful high-level thinking.  In terms of Bloom’s taxonomy, judging the strengths and weaknesses of an analogy could be considered Analysis and/or Evaluation, both of which are high up on the scale of cognitive challenges (Crowe et al. 2008).

(2) It doesn’t require a perfect analogy, and thus doesn’t require endless searching for one.  Acknowledging the analogy’s limitations is built right into the exercise!

(3) If you want different students to work on complementary tasks and then teach each other, there are always two discrete tasks to assign: identify the analogy’s strength(s), and identify its weakness(es).

(4) It helps students appreciate a fundamental truth about modeling in science.  That is, we use qualitative and quantitative models (such as analogies) to explain and/or predict things; models are not complete or perfect representations of the things being modeled, but they may have value anyway. Indeed, they may even have value because they’re incomplete and imperfect.

As an example of dissecting an imperfect analogy, consider the treatment of exponential population growth in an introductory biology course.  The instructor might say that this works like the accumulation of interest in a bank account, and then ask students to identify ways in which this comparison is and is not apt.  Students who understand exponential growth will be able to articulate that a fixed interest rate means that the higher the principal is, the higher the monthly interest earned; likewise, a fixed per-capita growth rate means that the larger a population is, the more individuals added to the population each breeding season.  With appropriate guidance, students should also be able to identify points at which the analogy breaks down.  For instance, they should recognize that while interest rates set by banks may fluctuate a bit, per-capita growth rates are highly density-dependent, so no phase of exponential population growth lasts for long in the real world (with the possible exception of human populations).

In this example, the analogy’s strengths may be more obvious than its limitations.  Of course, the opposite might also be true, depending on the analogy chosen and the instructor’s goals.  In the first quarter of UW-Bothell’s introductory biology sequence, Dr. Jeff Jensen gives a lecture on Mendel and meiosis titled, “Why Mom and Dad Aren’t Like Buckets of Paint.”  He emphasizes that, if the popular 19th-century hypothesis of “blending inheritance,” were correct, genetic variability would be diminished, rather than enhanced, by sexual reproduction; thus, students see that the buckets-of-paint analogy is a poor one.  But is it completely irredeemable?  If students are pushed to salvage something from the analogy, they might note that, even though alleles themselves remain segregated (i.e., they are not blended), some phenotypes do resemble a blending of parental traits, as when red-flowered plants crossed with white-flowered plants yield pink-flowered plants.

(Feel free to leave additional examples in the comments!)

In conclusion, I highly recommend the intentional addition of imperfect analogies to your lectures.  It’s sort of like adding a new spice to a familiar dish.  Sort of, but not exactly.

7 thoughts on “Imperfect analogies: shortcuts to active learning

  1. Thanks for the super-flattering intro, Jeremy! Seeing my humor credentials front and center, I now wonder whether I should have tried to make this post funnier (e.g., “certain analogies may not simply be imperfect, but downright awful, such as…”).

  2. We have students in an introductory ecology course design their own experiments and we just began this semester requiring the groups to design an analogy that represents the big concept question their research is approaching. We will see when they do their final presentations whether this method helped them in understanding their primary conceptual models. We offered them some example analogies for different things ecological and pointed out where it applied but also where it fell down. We then encouraged them to examine their own analogies in a similar way. Thanks for the post.

  3. Thanks for this post! (I’m late in getting to read it.) When you first suggested having students analyze an analogy, the first one that popped into my head was interest rates. 🙂

  4. I can remember mentioning the analogy to interests rates in my class here in NZ, and got a bit of a blank look from my students. It occurs to me that they may have not thought carefully about interest on student loans yet, so the a careful explanation of compound interest may be useful… for its own sake.

  5. Pingback: I’m not an ecologist, but sometimes I play one on the Internet | My Track Record

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