Random conversation time

[TheGreatErenan]

It's because human beings are extremely complicated machines with extremely complicated brains. We are capable of swiftly processing information about many different subjects at once, and in fact, our brains function, at least in part, by forming associations between different things. So even if you are discussing one particular subject, ideas will arise in the course of that discussion that remind one or more parties involved in the discussion about something else with which they have an association formed with the first thing that was under discussion.

The usual example that occurs with me is that many scenarios remind me of various episodes of The Simpsons, much to my wife's eternal chagrin. If I begin a sentence with "That reminds me of..." she immediately knows that the ending of this sentence will be "...an episode of The Simpsons." If I go ahead and explain the connection and relate the details of the episode, she will invariably start thinking about something else and completely ignore me, because she is no longer interested in hearing me describe stuff that happened in that show, having heard it one too many times.