Not all milk cartons are made the same. Some have the folded-in spouts and others have the twist cap spout. I have a learning history with both. Day in and day out, I engage in a similar chain of events when grabbing the milk carton from the fridge and pouring milk on my cereal. This routine would seem almost mindless, automatic and yet, through behavioural processes, I discriminate between the two types of cartons: the one with the cap I shake (and no milk spills out) and the other, I do not. Today however I got mixed up and I accidentally shook the carton with the folded spout. The consequence of my error? Milk everywhere.

I won’t cry over the spilled milk; rather, I’ll consider the over-generalization that occurred. Both types of cartons share common features: tall, slender shape, waxed white cardboard, liquid inside. In my error, these features acted as the stimuli that set-up my ‘shaking of milk carton’ behaviour. Failing to notice the lack of twist cap, I acted as I have in the past with a twist cap carton.

This is an example of a stimulus control error that occurs in our lives from time to time. Minor accidents, “slip of the tongues” and mix-ups occur when common features of similar stimuli cue new behaviour. In some cases, our errors are quickly “caught” and punished. It’s how we are corrected and learn not to do that behaviour under those circumstances the next time. In my example, I was inconvenienced by having to clean up. I won’t be spilling milk that way again!