reciprocate.

reciprocate: to act, feel or give mutually in return
reciprocal: a number that when multiplied by a given number, gives you 1

reciprocal altruism, reciprocal agreement, reciprocal cross, reciprocal inhibition, reciprocal translocation... so many kinds of reciprocals which basically means giving back in return.

How much do you give in return? Is it too little, or too much?

"The immediate emotional rewards motivating altruistic behaviour and partnerships will be the tendency to like others, to form friendships, and to act altruistically towards friends and likeable acquaintances" But as time goes by, and nothing to given mutually in return, cheaters form and then reciprocity will end (relationship ends).

Sometimes i think too much. haha!