The science of addiction: Do you always like the things you want? – BBC News

The most startling evidence that the dopamine system fires wanting, and not liking, comes once again from the unfortunate laboratory rat. In one experiment, Kent Berridge attached a little metal stick to the rat cage that, when touched, delivered a minor electric shock. A normal rat learns, after one or two touches, to stay well away from the stick. But by activating the rat’s dopamine system, Berridge was able to make the rodent become engrossed by the stick. It would approach it, sniff it, nuzzle it, touch it with its paw or nose. And even after the minor shock was received, it would return time after time within a five- or 10-minute period, before the experiment was stopped.