Defining key terms in Ecological Psychology

Andrew Wilson and I had a tiff on twitter about whether "Affordances" are by-definition "perceivable". Well... backing up... it was a tiff about whether it is fair for a researcher to start talking about something as an example of an affordance, when they have not bothering to demonstrate that the thing in question is perceived. This actually has deep implications for all the key terms in Ecological Psychology. As it is the type of thing you can't really discuss in 240 characters, we decided to return to the blogosphere. Who knows, maybe we can crank out a second blog-driven co-publication when this is done!*

I am extremely sensitive to the problems that occur in a theory when terms start to get mutually inter-defined. You quickly end up with tautologies, and tautologies stop your theory from being a theory in any proper sense. My post-doc advisor and occasional co-author Nick Thompson wrote about this problem extensively in the context of learning theory and evolutionary theory and other contexts in psychology. I don't think any prominent members of the Eco Psych community have such a problem when they are doing research. However, when they start writing theory, the problem pops up fairly often, and it is behind many of the long-term disputes in the literature. The temptation to inter-define terms is strong, because when terms are mutually defined, deduction is easier, and that makes the theory feel intellectually safe and well-founded. However, that feeling is misleading in a scientific context. you can't test things that are deducible from each other, so if you find yourself just stating things that are true by definition, you don't have a theory anymore, because the exact part this is supposed to be testable can't be tested. The way out of this is to rigorously ensure that your terms point to things that can be verified independently of each other, leaving it open for testing whether the things in question relate in the manner proposed. 

Tautology Part 1: Cognitive psychology and going to hell

One of the many problems with cognitive psychology, as practiced, is the frequent use of tautological explanations - a 'tautology' occurs when a thing is used to explain itself, and it is often called a 'circular definition'. The problem was mentioned in the comments section on this other blog, and Mike Samsa said:

For example, positing that the impulsivity in ADHD is caused by an impaired executive function - this doesn't really tell us anything useful when we define the executive function as something which governs self-control and the ability to resist impulsive urges.

This is a great example! In class, however, I have a really hard time getting my students to understand the problem. Alas, no matter how many examples I provide from psychology, about half the class still thinks the tautological claims seem reasonable. However, I have come up with an example that seems to work for all the students. I live in a somewhat religious area, but I suspect this would work just about anywhere.