In a world where you can watch what you want when you want, The Traitors has once again made television appointment viewing. The finale of the Celebrity edition, that saw Alan Carr bumble his way to the finish line, was watched by a staggering 15 million people.

Ahead of the new series starting on Thursday 1 October on the BBC, we spoke to three of our academics about strategy, psychology and why the show captures the public’s attention:

• Dr Mehmet Mars Seven, a Lecturer in Economics who specialises in game theory
• Dr Caroline Catmur PhD, Reader in Cognitive Psychology
• Dr Emma Bielecki, Senior Lecturer in Nineteenth-Century French Studies

“Consider how others will react to your choices, and play the long game” – Dr Mehmet Mars Seven

Players publicly vote to eliminate a suspected Traitor. Why might a rational contestant follow the majority even when they privately believe the group is wrong?

Deviating from the majority has two main effects. If the eliminated person turns out to be a Faithful, you can always say, “Look, I was right,” so you gain reputation. But if the eliminated person was a Traitor, this puts you under the spotlight immediately. So, your action will be one of the first things to be evaluated after the vote.

The important thing is that you need to have a good reason to vote for someone.

A person’s vote matters most when they’re the pivotal voter. To give an example, if Alice knows that Bob is going to be eliminated regardless of her vote, the immediate cost of joining the majority may be very small. It may be rational for her to vote for Bob even if she believes that he is a Faithful.

The Traitors secretly remove one contestant each night. How should they balance eliminating their strongest opponents against the risk that an obvious choice will reveal their strategy?

Removing the “best” Faithful can be beneficial at first, but upon closer thought, one must consider the response it will create after the elimination.

In games of incomplete information such as The Traitors, sometimes randomisation can be optimal, meaning, for example, tossing a coin to decide who to remove. This can be especially helpful in The Traitors because randomisation may prevent a Traitor from giving themselves away through their behaviour.

Contestants often form alliances despite knowing that any ally could secretly be a Traitor. What does game theory tell us about cooperation when trust can never be fully established?

In game theory, cooperation can be sustained even if trust isn’t fully established. This is usually done by finding a mutually beneficial outcome and making a deviation carry a future cost, for example, via retaliation. Here the keyword is “mutually beneficial outcome,” which doesn’t mean that this outcome is equally beneficial to everyone.

Actually, both Faithfuls and Traitors have an interest in helping to build the prize fund, so they all have a reason to cooperate. But they also have a reason to defect when the timing is right.

A Traitor may want to keep a Faithful ally alive because that ally may provide a beneficial vote. A Faithful may benefit from that protection while remaining suspicious of the ally’s role. So, cooperation benefits both even though neither of them trusts the other, because each of them understands the other’s incentives to cooperate!

The Traitors cannot be reduced to purely technical game theory because human psychology also matters massively, as players have to infer emotions and intentions.

In summary, the main game theory message in The Traitors is not just to consider what the best action is to survive one more round, but also to consider how others will react to your choices and to play the long game.

“People who are better at detecting others’ lies are often good liars themselves” – Dr Caroline Catmur

The Faithful must identify who the Traitors are largely by how they speak and behave. Generally, how good are people at detecting deception?

People are, generally, very poor at detecting others’ lies. Most people are no better than chance at detecting when someone else is lying.

One thing that does seem to make people better at detecting others’ lies, is being a good liar themselves. We think this is probably a practice effect, where people who have had a lot of practice at working out how to lie convincingly are also better at spotting those clues to lying in other people.

In our work, we found that the main clue that someone was lying was how long they took to answer a question. Basically, it takes longer to think of a convincing lie. People who are good at lying, are quicker at coming up with a convincing lie so that clue is harder for other people to spot.

Contestants publicly discuss and vote on whom to eliminate. Why might people conform to the majority even when they privately disagree?

Conformity to the majority is made up of compliance (appearing to conform in public but privately disagreeing ) and acceptance (changing your own belief to conform in both public and private). We probably see both in The Traitors but compliance is psychologically more interesting.

Compliance in everyday life might happen for several reasons, for example including the desire to be accepted by the group, not wanting to ‘stand out’, or not being very sure about whether one’s own belief is actually true, so going along with the majority because they appear more confident (but without actually changing one’s mind).

In The Traitors there is the additional pressure that standing out, by disagreeing with the majority, could be very costly indeed as it could make one a potential target for elimination on subsequent rounds.

“The Traitors allows us to explore some ineluctable aspects of the human condition” – Dr Emma Bielecki

Are deception and betrayal an enduring aspect of storytelling? Do we simply like to watch people deceive one another?

I think for as long as people have been telling stories they've been telling stories about betrayal. Presumably this is because it is quite hard to get through life as a human without at some point both betraying someone (perhaps oneself) and being betrayed. Many of us know what the experience is like from both sides; we've been Traitors and we've been Faithfuls. We can project ourselves into the story from different angles.

We have a contemporary preoccupation with fake news, bot farms, misinformation and deep fakes and every day we have to confront questions about where to place our trust. The Traitors is a space where we can engage with those questions in a ludic, risk-free way. But also, I think we basically like to watch people deceive each other, as long as we're not being deceived. The pleasure of watching The Traitors is linked to the pleasure of being able to say “I know something you don't know”.

Are shows like The Traitors a natural successor to Agatha Christie’s murder mysteries?

I think we have to distinguish between the experience of playing and watching The Traitors. The appeal of playing the games, I think, does overlap to a very considerable extent with the pleasure of reading an Agatha Christie. French thriller writers Boileau-Narcejac say somewhere that the deep metaphysical root of crime fiction's appeal is that we don't tolerate ignorance very well; the greatest pleasure is the pleasure of coming to knowledge, of revelation.

But the pleasure of watching other people play the game is something else. I think that's about power, the thrill of being in possession of a secret, not the thrill of solving a puzzle.

I think that The Traitors as a show allows us to explore in a fun, safe way, some ineluctable aspects of the human condition that are not, in real life, very fun or safe at all, like betrayal and murder.