I'll restate my very simplistic understanding:

• Your genes decide how well you make factories for biochemicals, and how well these factories make biochemicals.

• Learned behaviours require hardwiring between neurons, turning them into networks.

• Hardwiring requires the presence of biochemicals to trigger the process of new connections.

• The amount (and possibly quality) of these biochemicals produced in responding to stimulii influences the building of learned behaviours.

But, as you have pointed out, there is a cumulative feedback process in which the stimulii (and previously established responses/behaviour) change the way the factories work.

Some well known behaviours never occur because the threshold of learning is never reached. About 11% of Chinese have a genetic 'peculiarity' that means that they cannot process alcohol beyond the stage of toxicity. The first drink they take will make them ill. They will not repeat the experience, and thus never become alcoholics.

You can't be me, I'm taken