What does linking mean?

I watch a Khan Academy video before sleeping. Does this mean that I am going to start linking Khan Academy (or Math) with sleepiness?

• I used to watch an episode  of a comedy series before going to sleep. But lately, I started to  watch a Khan Academy video, usually something math-related.  Does this mean, that in the long term, I might start to assimilate the  subject of the video and/or Khan Academy with being tired? I am going to start getting sleepy during Math lectures? In that case,  I will go back to the series!

• Answer:

  I doubt that very much, but it isn't entirely outside the realm of possibility. What you're referencing is http://en.wikipedia.org/wiki/Classical_conditioning (Pavlovian conditioning). The classic experiment with Pavlov's dogs involved a ringing bell every time they were fed. Consequently, after conditioning, when the bell was rung the dogs would begin to salivate even when food was not present. As mentioned in the Wikipedia article above, it was originally thought that the conditioned stimulus becomes so deeply associated with the unconditioned response, but it hasn't been shown to be that simple. It's probably more accurate to say that the conditioned stimulus predicts an unconditioned stimulus. Could this mean that eventually when you think about Khan academy you think about bedtime? It's certainly possible. But every time you think about brushing your teeth, do you get tired? What about eating dinner? People are fairly complex beasts and simple prompting doesn't necessitate a hardwired response. From my entirely unqualified point of view, I would say that if bedtime is the only time you ever think about math, there may eventually develop some connection. But chances are you think about a lot more than that, and are reminded constantly of it during the course of your life. Your brain is perfectly capable of sorting through these complexities without being victim to an uncontrollable physical response. For what it's worth, I did the same thing with Robert Sapolsky's lectures on human behavioral biology, and I can say with confidence that thinking about evolution doesn't make me tired. :) As a pure thought experiment, it's actually a very interesting question though, and there may indeed be studies in classical conditioning with human subjects which test the exact same thing, but I'm not aware of them.