I am on a mission to spread the news of this transformational (yes!) exercise for all teachers of all subjects, but especially scientists.

It is called the Wason* 2-4-6 Task, (I’ve seen it referred to as the 2-4-8 test). It is the best exercise I’ve ever seen for demonstrating the perils of confirmation bias.  It also stimulates great conversations about the importance of controls, the careful examination of assumptions, the importance of negative results, and, the biggie, how critical it is to attempt to DISPROVE your hypotheses, not prove them.   When I’ve done it with colleagues as well as students, it has also stimulated discussions about experimental design, and different kinds of creativity, and how having multiple hypotheses can help prevent falling dangerously in love with one.

There are many versions on the web; I like this site:

https://explorable.com/confirmation-bias

It has a very nice explanation and a charming video. If you can, stop it before he gives the answer (at 2’55”) – see if you can guess the rule.

I cannot recommend this exercise more highly.  I do it with every new student that crosses my path, as well as friends and family (I am such a nerd).  Everyone, without exception, thinks it is a fun and intriguing experience.  And forevermore, you can help students realize when they are thinking in a biased way just by saying “2-4-6” so it also provides a handy tool for reinforcing the ideas.

Go forth and joyously spread the news of the Wason 2-4-6 Task!

*Peter Cathcart Wason, 1923-2003.  Among many achievements, he coined the term “confirmation bias”.