"Our broad conclusion is that testosterone causes men essentially to be stingy," says Karen Redwine, a neuro-economist at Whittier College in California [...] To make this case, Redwine and her colleague Paul Zak, at the Claremont Graduate University in California, gave a testosterone-containing gel to 25 male university students, and then tested their generosity.

The students then played a simple economic game with another participant via a computer. One volunteer is tasked with splitting $10 with another volunteer in any way he likes. The other volunteer either accepts the offer or rejects it as unfair, in which case no one gets any money. Each volunteer played this game in both roles, on and off the testosterone gel.

Overall, the testosterone cream caused a 27 per cent reduction in the generosity of the offers, from averages of $2.15 to $1.57, Redwine and Zak found.

The article also described how oxytocin, the so-called cuddle chemical, can actually boost generosity: Link

Neurobiologist Larry Young of Emory University, Georgia, explains:

Animal testing is beginning to shed light on the complex neural and genetic components of love in the same way they have led to pharmaceutical therapies for anxiety, phobias and post-traumatic stress disorders.

The behavioural scientist Professor Larry Young, of Emory University, Georgia, writing in the journal Nature, said: "For one thing, drugs that manipulate brain systems at whim to enhance or diminish our love for another may not be far away."

Experiments have already shown a nasal squirt of the hormone oxytocin enhances trust and tunes people into others’ emotions.

Link