My hypothesis: people are not trained as a young person to seek pleasure, they're genetically programmed to do so; many (most?) modern "foods" are engineered and designed to short-wire various naturally evolved systems by introducing artificial stimulus, thus creating closed feedback loops. The baseline is amended upwards with each iteration, and what was normal yesterday is under stimulating now.

> [...] Scientists call this phenomenon, “supernormal stimulus.” It is what happens when an exaggerated version of what appeals to evolutionary instincts can cause some one or some thing to engage in behavior counterproductive to its own survival (or the survival of its genes).

MORE!

http://joyousandswift.org/hyperstimulus/