Thanks for the memory

A humble flat worm that can survive decapitation demonstrates intriguing powers of recall.

- MARC WILSON

Planaria. What? You don't know your planaria from leeches, slugs or detritus worms? No, I don't know what a detritus worm is, either.

For the purpose of today's lesson let me introduce planaria - singular planarian, a kind of flat worm.

I first learnt about it in my second-year social psychology class. One of my academic idols, Frank Walkey, taught us about designing a good research study and among other things he introduced us to “demand characteristics” and “experimenter effects”, illustrated with the research of people like Martin Orne and Robert Rosenthal.

Demand characteristics occur when research participants respond to the research context in ways they think they're supposed to, and experimenter effects happen when people behave in particular ways reflecting the behaviour of the experimenter.