[scott_s]

How much of it did you read? They go into things like when people spend money on charitable causes, they tend to be happier with the purchase than when they spend it on material goods. One of the take-aways is: spend money on thing which will promote the internal happiness that you mentioned.

[NathanRice]

Giving a gift to someone buys you their attention for a period of time, and some degree of positive predisposition under circumstances of ambiguity. Respect still has to be developed based on observation of character and discernment of intent. A rich heir who gives to generously and has a negative character is probably attempting to buy influence or assuage a guilty conscience. A guy buying drinks for every attractive girl in a bar is probably slimy. Those acts have no payoff unless someone responds in the manner that the act was performed to induce.

My hypothesis here is that the happiness is coming from creation and strengthening of interpersonal connections as a result of post giving interaction, not from the act of giving itself. I would be interested in studies where someone spent money on others in versus themselves without the opportunity for interaction or feedback upon giving. I suspect that would confirm my hypothesis.