In the Ivory Tower, lots of academic types have tried to get a handle on exactly what impulse buying is and why people engage in the behavior. That turns out to be a very un-simple task. I won't even go into how impulse buying can be a variety of compulsive buying. It can all get very confusing. I can tell you that humans are prone to purchase certain classes of products on impulse.
People also get impulsive about stuff on sale .
I mean, only in other people, of course. And pure impulse buying is unplanned. It just happens. At least, it does out there in the bricks and mortar world. There's a fellow, Paul Romanchuk, who has this scheme to make online shopping a more 3-D experience in order to stimulate browsing and impulse buying.