When Novak Djokovic was talking about why he won’t get the coronavirus vaccine, there was something about the way he was behaving that seemed familiar. It reminded me of something else, something I’d seen and felt before. Djokovic told us his refusal was about what he did and didn’t want to put in his body, but could it be something else entirely?

What Djokovic said was this: he has always been a student of wellbeing and his decision was based on the positive impact things like changing his diet have had on his health. “I'm trying to be in tune with my body as much as I possibly can," he said. He also said he was not against vaccination as such but supported the right to choose what you put in your body.

There’s a few things you could say about of all of that, the most important of which is that any student of wellbeing should know that billions of doses of vaccine have been administered, they’ve saved countless lives and the risk of side effects is vanishingly small. For Djokovic, having the vaccine is also clearly the most practical and sensible thing for him to do because it will allow him access to tournaments.

And yet he won’t. In fact, he says he would rather miss out on future trophies than get the vaccine. He also said he was willing to forego the chance to become statistically the greatest male tennis player of all time by winning the most Grand Slam titles. Perhaps Djokovic would call it sticking to his principles but perhaps we should just call it what it is: stubbornness.

I suspect it’s stubbornness for a number of reasons, the first of which is personal. Ask any of my friends and family what my flaws are and, if you have the time, they will work their way through the list and eventually get to stubbornness at number one. Undoubtedly, my stubborn streak has helped me pass exams and get to the end of 10ks and so on, but it has also caused problems too and, like Djokovic, it can even lead you to situations where you’re working against your own self-interest.

The other reason I suspect stubbornness is because it’s more likely to strike men than women. There’s research at Caltech which established the connection between higher levels of testosterone and the tendency to rely on intuitive judgments rather than longer-term reflection. Essentially, the conclusion of the research was that testosterone increases the feeling you’re definitely right and your determination to stick to it. Man means more testosterone means more chance of being stubborn and I’m not changing my opinion about that ever.

The consequences are obviously personal – Djokovic could miss out on becoming the greatest tennis player of all time – but there are bigger consequences too. I remember a consultant psychiatrist once telling me about research he’d seen in the States that looked at all the international conflicts of the last 50 years and concluded that the more women are involved in leading a society, the less militarily aggressive the society is. In fact, the research, which was published in the Journal of Conflict Resolution, showed that if the percentage of women in a legislature increases by 5%, a state is nearly five times less likely to use violence internationally.

My psychiatrist friend was understandably cautious about making any generalisations about the research but he did suggest that – perhaps – it was a preponderance of certain qualities in men that was causing the problem; his theory was that qualities more likely to be associated with men such as competitiveness, and stubbornness may explain the male approach to international relations. More stubborn men therefore more bloody war.

Naturally we should be careful about a conclusion that applies to everyone. But the consequences of stubborn men, men who will not budge, are all around us. It’s happening to Novak Djokovic. It’s happening in Ukraine and Russia. And it’s happening in a country that’s led by a man who stubbornly refuses to accept that during lockdown he went to a party.

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