Dr Nick Wright and colleagues at the Wellcome Trust Centre for Neuroimaging at UCL carried out a series of tests on pairs of female volunteers who had never previously met. The tests required participants to work together to decide whether an image displayed in front of them contained a specific visual target.
The tests took place over two days, spaced a week apart. On one of the days, both volunteers in each pair were given a testosterone supplement; on the other day, they were given a placebo.
The researchers found that higher levels of testosterone were associated with individuals behaving egocentrically and deciding in favour of their own selection over their partner’s.
As Dr Wright explained, “Our behaviour seems to be moderated by our hormones – we already know that oxytocin can make us more cooperative, but if this were the only hormone acting on our decision-making in groups, this would make our decisions very skewed.
"We have shown that in fact testosterone also affects our decisions, by making us more egotistical. Most of the time, this allows us to seek the best solution to a problem, but sometimes, too much testosterone can help blind us to other people’s views. This can be very significant when we are talking about a dominant individual trying to assert his or her opinion in, say, a jury.”
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