Here's a video of a TED Talk my daughter Isabel was telling me about.
The issues of motivation it raises are perhaps not directly related to language learning, though perhaps there is a connection between what is said and how you respond to what your learners say. If you don't respond to it at all, not even nod, perhaps you're suggesting (unintentionally!) that what the learner had to say was of zero interest to you…? And what effect will that have on their motivation?
With a fairly advanced class of adults (say, above FCE?), though, it might make for an interesting class discussion, which you might start by getting your learners to summarise and present what Dan Ariely is saying in his talk.
The talk is also interesting, I think, from a language teacher's point of view. How is our performance evaluated, by who, and what effect does that have on our motivation?