Politicians need to realise, and they need to realise it soon, that they can't unite people through identity politics. They can only divide, writes Claire Lehmann.

In the 1970s, a famous social psychology experiment established the in-group/out-group bias.

In what is now called the Minimal Group Paradigm schoolboys were assigned to two different groups according to whether they preferred the abstract paintings of Klimt, or the abstract paintings of Klee. When the two groups were pitted against each other in games where they could allot small amounts of money to each other, they consistently allotted more money to their in-group, despite the meaningless distinction between them.

This in-group/out-group bias was so robust the same results were found when the two groups were assigned with a coin toss. And further psychological research shows that it doesn't take much for such groups to start really derogating each other.

This is why today's identity politics can be such a worry. It is a scourge of superficiality, and you see it whenever words like "straight", "white" or "male" are used as insults, or as apparent checkmates within debate. You can see it when Bill Shorten grabs same-sex marriage to champion, as if he hadn't spent years indifferent to it, waiting for the issue to go away.

Every time we group people according to crude social categories we are setting up an in-group/out-group bias. When one group is earmarked for special treatment by policy makers, it can set up resentment in those who miss out, leading to a cycle where both groups start to compete with, stereotype, and dehumanise each other.

We can see this today with women's interest groups who feel aggrieved and dehumanised by men; and the proliferating men's groups who feel aggrieved and dehumanised by women. Yet this tribalism is by no means limited to gender.

The left do not have a monopoly on identity politics, but it does originate with them. Not from left-wing politicians, but from university campuses, in segments of academia where the preoccupation with gender and race verges on obsession. Yet while identity politics' home is not on the right, it has become a plague that does not discriminate.

In recent years, journalists from News Corp have attacked the ABC and Fairfax on a daily basis, oblivious to the fact that normal people don't care about media infighting.

Long before identity politics, left-wing ideology had two things going for it: solidarity and universalism. "Universalism" is an abstract term, but it's a simple concept. It simply refers to the fact that it didn't matter if you were a sheep-shearer in Australia, a miner in Wales, or a railroad worker in the US - if you were going to sacrifice your life (and lower back) to a faceless boss, then you had to get paid. But now the battles of worker's rights have largely been won. And these successes have left an ideological void.

James Bloodworth, a writer in the UK, has argued that identity politics has emerged as the left has become more middle-class. Activists who populate universities and the press no longer focus on material inequalities because they themselves are relatively well off. But it's not just because activists are middle-class that they focus on easy topics of gender, sexuality and racism.

It's hard to come up with solutions to today's policy issues. It's hard to address growing budget deficits while addressing socio-economic inequality. It's hard to figure out what to do about climate change whilst creating jobs.

Focusing on identity is simply easier than coming up with original ideas or workable policies. And this is why identity politics has spread to the right. In 2015, the low hanging fruits of policy have all been picked, and the problems that are left over are wickedly difficult. In this context, a retreat into a quagmire of tit-for-tat personal attacks is understandable. These problems have no easy solutions, have no political winners, and difficult trade-offs emerge at every corner.

No wonder the electorate feels unimpressed and dissatisfied. Our politicians keep trying to score cheap points by pigeonholing their policies and marketing them back to us. But if they don't stop, community detachment will continue apace. Protest parties will proliferate. Left-wingers will turn to libertarianism, and disenchanted conservatives will turn to independents.

Politicians need to realise, and they need to realise it soon, that they can't unite people through identity politics. They can only divide.

Claire Lehmann is a Sydney-based freelance writer. She is currently completing a master of forensic psychology. You can follow her on Twitter @clairlemon.