Socks and underpants, as usual. Love?

Beware humans bearing gifts - New Scientist
You won't be surprised to be told that academics in cognitive psychology departments the world over are busy producing evidence about the power of reward and its connection to dopamine, because it's something we've all experienced directly - albeit without the technical description. To be rewarded with a gift is to be subtly told that someone loves you, and we love nothing better than to be loved. Even adults will be momentarily taken back to a warm, childlike feeling of deserving the treat that has been given.