The Dreaded Dichotomous Key

Oh, dichotomous keys. You’re like the cat who came back – I just can’t avoid you.

Have you ever used a dichotomous key? The idea is simple: use a series of mutually-exclusive statements to identify something. The execution is often more painful.

And this is a nice one...

Popular as torture devices in Invertebrate Zoology courses worldwide (have you identified over 300 species of Digenea using a dichotomous key? I have. I’m so much fun at parties), I’ve never seen them used successfully in museum exhibits and interactives. And yet they keep showing up. Maybe it’s just my experiences, but there has to be a more engaging way to show visitors how scientists identify and classify than with a awkward flowchart.

Several years ago, while working at a large natural history museum, I helped plan a new series of touch carts for the Geology Hall. One of the conversations went something like this:

Geologist 1: “We should put out different mineral samples that visitors could identify using a dichotomous key.”

Geologist 2: “And let’s include some that can’t be identified by the key provided. Then visitors will realize that they have the wrong key and they’ll understand more about identification!”

All the Geologists: “Yes!”

Katie’s Internal Monologue: “No!”

Frustrations about setting visitors up for failure aside, it was a bad idea for that space and audience. I suggested some alternatives, the dichotomous key idea was forgotten, and all remained right in the geological world. But at least once a year I come across another dichotomous key interactive, and they never quite work.

Here’s the latest:

“Schlangen,” [“Snakes”] Freiburg Naturmuseum (Frieburg, Germany)*

The goal: to identify the species of snakes represented by plastic snake heads using the dichotomous “tree” on the table. This is done by doing tedious exciting things like counting head scales.

I like the tree idea for a classification activity – it’s much easier to follow than the standard dichotomous chart, and simple enough that it’s not overwhelming. But then there are the snake heads to identify:

Good luck.

This activity almost made it. With better snake head models (e.g. ones in which the scales haven’t been worn away), or possibly close-up photographs, it might have been fun. But instead it was frustrating with little success, and the visitors I watched never stayed longer than a minute.

So I continue wondering – can dichotomous key activities work in museums? Have you seen/created/participated in any that were fun and made sense? And if dichotomous keys aren’t the answer, how can we better talk about identification? Or do we even need to?

*Disclaimer: The Freiburg Naturmuseum is lovely. And if they ever read this post, I thank them in advance for their gracious good humor.

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2 thoughts on “The Dreaded Dichotomous Key

  1. Pingback: Walking the Phylogenetic Tree |

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