He said that people take psychology courses because they want to understand their problems. Most people figure themselves out after a course or 2 and do something else. Some people's problems are more complex so they take more courses. And then when they've figured themselves out they say, "What do I do for a degree? Well I have all of these psychology courses..."
This uncle had a PhD in psychology and was a prime example of his own theory.
Cheers,
Ben