The division between right and left around the world has rarely felt more polarised. Of course there have always been differences between people on the different ends of the political spectrum, but now it seems they are living in different worlds entirely. This is perhaps related to the tendency for those on the right to focus on the past and to strive for a world that once was and the tendency for those on the left to do the opposite.

Take two of the most famous political slogans of recent times: Barack Obama’s “Yes we can” and Donald Trump’s “Make America great again”. While Obama’s message evokes glimpses of a prosperous future, Trump’s expresses a nostalgic outlook towards the past.

In the UK, the successful Brexit campaign, which was largely led by conservatives, famously called on people to “take back control”, while the Labour party has just launched its local election campaign under the slogan “Britain’s future”.

The pattern is similar around the world. In South Africa, the right-wing Freedom Front Plus has recently carried the slogan “Stop the decay”. For the upcoming presidential elections in Mexico, the left-wing National Regeneration Movement is mobilising voters with “United for the transformation”.

In a recent study, I explored whether, within the general public, people on the right evaluate the past, present, and future differently compared to people on the left. I asked a sample of 1,200 people to judge different periods of history.

They were asked about the period from 1950 to 2000, the present day and the near future (by giving their view on what society would look like in 25 years). I drew participants from the US, UK, Italy, South Africa, Mexico and Poland – countries with different economies, cultures and political regimes.

In every country, right-wingers evaluated the recent past more positively than left-wingers. In the US, Poland and the UK, by contrast, left-wingers were more optimistic about what humanity could achieve in the near future.

Interestingly, the effect on the left did not emerge in Italy, Mexico, and South Africa. Therefore, while the right’s more positive view of the past seems to be shared across countries, the left’s higher optimism does not.

The glorious past

In one experiment for the study, a group of participants was prompted to look more favourably to the past. These participants did not appear to be more open to right-wing opinions after having done so. This suggests that the connection does not run in this direction. Being more nostalgic about the past does not predispose people to endorse right-wing beliefs.

On the other hand, another experiment encouraged a group of participants to freely reflect on their political opinions. Right-wing participants from this group became more nostalgic about the past when given this prompt.

Left-wing participants became less so. This suggests that endorsing right-wing opinions at the start leads people to be more nostalgic, while endorsing left-wing opinions does the opposite.

One last experiment explored nostalgia in more detail. Here I considered two potential forms of nostalgia. Some people may be nostalgic about traditional communities, about the old hierarchical order, about stronger family ties and about traditional culture. Other people may be nostalgic about the state of the economy, hearkening back to a time when governments tended to intervene more.

Is the right nostalgic about tradition, the economy, or both? In my experiment, it was people on the left, not the right, who were more nostalgic about the economy. Those on the right had greater nostalgia for tradition.

The data does also show that the economic nostalgia on the left is not as strong as the nostalgia for tradition on the right, explaining why the right can, overall, be considered more nostalgic than the left.

These findings help explain why it’s so common for right-wing politicians to appeal to voters with promises to take them back to the good old days, and for left-wing slogans to mobilise voters towards building a better future – and perhaps offers lessons to those politicians who’d like to reach across the divide.

Francesco Rigoli is Reader in Psychology, City, University of London.

This article was first published on The Conversation.