Before they went to the button, the slot machine guys knew that the handle was an addictive mechanism. The button, it turns out, does have the same addictive properties when you push and you don't get money. You push, push, push, and you get money. It works just fine with the computer. You have this little button, and you click, click, and click.
Nothing happens at the time.
You get used to it, but you still keep this clicking thing and you also have oneness with the computer. I first noticed this phenomenon during the command-line interface period of the PC business. The only GUI guys were Mac users, and they were addicted to the Macintosh. You couldn't get them away from it, and they would never go back to the command line. It was obviously due to the addictive mechanism of this little mouse.