Volunteers who were administered propranolol, which is typically given for heart disease, plus anxiety and panic, appeared to be less subconsciously racially prejudiced than another group treated with a placebo.

Propranolol interrupts nerve circuits that govern functions such as heart rate and the part of the brain involved in emotional responses, so the study has led scientists to conclude that racism is fundamentally a symptom of fear.

The research, undertaken by Boffins at Oxford University, who asked volunteers to categorise positive and negative words, plus pictures of black and white people.

The results, published in the journal,  Psychopharmacology, showed more than a third of volunteers were biased towards being non-racist, but only at a subconscious level.

Experimental psychologist, Dr Sylvia Terbeck, described the research as a breakthrough in understanding the processes in the brain linked to implicit racial bias.

“Implicit racial bias can occur even in people with a sincere belief in equality. Given the key role that such implicit attitudes appear to play in discrimination against other ethnic groups, and the widespread use of propranolol for medical purposes, our findings are also of considerable ethical interest.”

The study also proved the drug cannot modulate explicit bias.

This was gauged through a “feeling thermometer” – a psychological tool used to assess explicit prejudice – where volunteers were asked to rate how “warm” they felt towards different groups.

Dr Chris Chambers, from the University of Cardiff’s School of Psychology, urged caution with the results.

“We don’t know whether the drug influenced racial attitudes only or whether it altered implicit brain systems more generally,” he said.

“And we can’t rule out the possibility that the effects were due to the drug incidentally reducing heart rate. So although interesting, in my view these preliminary results are a long way from suggesting that propranolol specifically influences racial attitudes.”