Does testosterone increase generosity instead of selfishness?

An interesting experiment has been done on women. A group of female volunteers received an injection of testosterone, the male hormone, associated with aggression in rodents, while, as usual, a control group received a placebo.

Among the women who did not know what was all about, those under testosterone behaved more generously than the control group (offering an average of 50 cents more in the test's deals). However those women who were told that had been injected testosterone, whether true or not, behaved more aggressively and offering up to 1 dollar less in their bargains.

These results contradict an earlier experiment in which young men did behave stereotypically macho under the effects the hormone. This other test did not consider bias though.

Source: New Scientist (I could not find the original paper, though I know it's been published in Nature).