A few days ago one of my colleagues mentioned a scholarly article he'd read the night before.  Researchers were attempting to show a genetic link for thrill-seeking (novelty-seeking) behaviour with some success.  That is, for their definition of "novelty-seeking" they seemed to have discovered a relationship between (IIRC a particular gene) and the behaviour in question.

Obviously with my academic background this was ear-pricking-interest-seeking time :) .

Our argument basically came down to a question of what "instinct" means.  He was arguing along the lines that the entire emotional pattern of "boredom" was an inherited instinctual (absolute) trait.  That is, if you were born a "thrill-seeker" you would always be bored and constantly driven to explore new things.  But what's more, he was essentially saying that the "emotion" of boredom was an irreducible "instinct", that is, it's operation was an atomic personality trait that would always express itself.

Thing is, what's an "emotion", and why is it irreducible? Just because if feels like it is?

As I've discussed before, the mind is an iterative process which is constantly feeding information up and down the perceptual pathways and predicting what should be coming "next" for each level of operation.  When our expectations are violated, our mind searches for new models that can match the violated expectations.  When our expectations are met (when our predictions are correct) we are generally content, experiencing less stress.  But our expectations are never met at all levels for all experiences (until we achieve omnipotent wisdom, anyway).

So what happens when most of our immediate expectations (predictions) are correct?  When everything is familiar and well-understood, some people find the experience fulfilling and satisfying, others find that they want to discover other, possibly better models.  My suggestion is that it is the second behaviour that causes the perception of "boredom" and causes us to "thrill-seek".

At the neurological level "On Intelligence" has some interesting attempts to explain the mechanisms.  In that model, neurons which are violated have a certain feedback strength, which would likely be swamped among more immediate concerns, but which can rise to prominence if there's nothing else to worry about (in my thesis rewrite see the section on sitting in a cafe for a fully-fleshed out example).  This pattern works both "up" and "down", so unsolved questions about the nature of the universe may start getting played with as you find yourself sitting waiting for a bus.

The interesting thing about the "On Intelligence" model is that it would be trivial to imagine a gene controlling the feedback strength of the neurons which are failing expectations... and a genetic "instinct" of "boredom" and "thrill-seeking" would seem to fall out automatically from the same model of perception as everything else... i.e. no special rules required, nothing particularly different, just tweaking a "parameter" to be someone who can "let things be" or needs to "find the underlying truth".

The model tends to "soften" the conclusion somewhat.  Yes, there would be a genetic predisposition, but if you are just tweaking the strengths of the neurological connections, then you would expect to see a wide range of different thrill-seeking levels, likely modulated by experiences sufficiently to mask many of the genetic effects.  We do see that in the real world, of course. We don't have a sharp divide between those who "seek thrills" and those who do not, everyone seeks deeper understanding of their universe, some just probe deeper and are willing to undergo a far greater risk than others.