Part four of the Expert guide to conspiracy theories from The Anthill podcast explores whether the internet has been a game changer in helping conspiracy theories go viral. First, though, we find out how conspiracy theories spread before platforms like Facebook and YouTube came along and gave everyone the power to broadcast their thoughts to the world.

It’s important to differentiate between the producers of conspiracy theories and the consumers, which philosopher Quassim Cassam talked about in part one of the series. The producers often push a political ideology. They are also very good at dressing up their theories in academic language. This can make it difficult for the non-expert to recognise a conspiracy theory as bogus and is important for their initial spread.

But what makes these ideas really take hold is the people that buy into them – the consumers. Annika Rabo, an anthropologist from Stockholm University in Sweden, tells us how people enjoy spreading conspiracy theories because it can make them seem funny or clever. Most people don’t just spout a conspiracy theory as they hear it, they will often adapt it to their situation – and their audience.

Michael Butter, American studies scholar at the University of Tübingen in Germany, gives us some insight into the history of how conspiracy theories spread in the 19th and 20th centuries. Some were preached from pulpits and incited riots. Then, advances in printing technology made it easier for conspiracy theories to spread. Publishers made money selling fanciful stories – some that were openly fictional, others that were fake exposés.

We also delve into the world of conspiracy theories as entertainment. Clare Birchall, reader in contemporary culture at King’s College London, talks us through literature in the 1960s, 70s and 80s that engages with conspiracy theories in a playful way and uses them as a device to tell stories. We find out how The X-Files did something similar in the 1990s.

The internet has changed the game for communication in terms of how quickly information travels and how it gives everyone a platform to broadcast their views. But Stef Aupers, professor of media culture at the University of Leuven in Belgium, explains that this doesn't necessarily mean conspiracy theories reach more people. In large part, this is because most people end up in echo chambers online. Nonetheless, these echo chambers help solidify people's views.

Correction: this podcast refers to the 2019 mass shooting targeting Mexicans in El Paso, Texas, as happening in El Paso, New Mexico.

The Anthill podcast is produced by Annabel Bligh and Gemma Ware for The Conversation. Sound design is by Eloise Stevens, with original music from Neeta Sarl and audio from Epidemic Sound. Thanks to City, University of London, for letting us use their studios. Special thanks to Clare Birchall, Michael Butter and Peter Knight who helped bring this podcast into being, and to the COST Action COMPACT for funding it.