According to the study, as happiness is a vague, abstract condition and in the end one won't know if the other person is really happy, it can cause frustration and thus unhappiness.
Psychologist Jennifer Aaker, lead author of the study said that a prosocial act can not only boost the happiness of the recipient, but it can boost the happiness of the giver as well, and that making someone smile is a concrete goal, they said, so it's easier to achieve.
The study was published in the Journal of Experimental Psychology.
Source: ANI