How Deluded are You?

Grand delusions: Why we all believe the weirdest things
The human mind is the perfect breeding ground for bizarre beliefs, so we shouldn’t be surprised that fake news has such a powerful influence

By Dan Jones
New Scientist 15 Nov 2017
https://www.newscientist.com/article/mg23631520-800-grand-delusions-why-we-all-believe-the-weirdest-things/



THREE Messiahs walk into a psychiatric unit… No, this isn’t the set-up to a tasteless joke, but the beginning of a study done in the 1950s by Milton Rokeach at Ypsilanti State Hospital, Michigan. Rokeach brought together three men, each harbouring the delusion that he was Jesus Christ, to see if meeting the others and confronting their mutually contradictory claims would change their minds. Two years and many arguments later, their beliefs had barely budged. For each Jesus, the other two were fakers, while they were the real deal.

As delusions go, the Messiah complex is extreme. Most delusions are far more mundane, such as an unfounded belief that you are exceptionally talented, that people are out to get you or that a celebrity is in love with you. In fact, more than 90 per cent of us hold delusional beliefs. You may find that figure shockingly high – or perhaps you see evidence all around, in the willingness of so many people to swallow fake news, in the antics of politicians and celebrities, and even among your Facebook friends. Either way, what exactly does it mean? Why are some of us more prone to delusions than others? How do false beliefs get a hold in our minds? And can we all learn to tame our delusional tendencies?

First we need to be clear about what a delusion is. “There’s a loose way of talking about delusions – like when we talk about the ‘God delusion’ – which simply means any belief that’s likely to be false and is held despite lack of evidence, or even in spite of the evidence,” says Lisa Bortolotti at the University of Birmingham, UK. The psychological take is more nuanced. Delusions are still seen as irrational, but they are also idiosyncratic, meaning the belief is not widely shared. That rules out lots of things including most religious beliefs, conspiracy theories and the denial of climate change. Furthermore, the idiosyncratic nature of delusions makes them isolating and alienating in a way that believing, say, a conspiracy theory is not. Delusions also tend to be much more personal than other irrational beliefs, and they usually conform to one of a handful of themes (see “Strange beliefs”).

Bizarre beliefs
At any time, around 0.2 per cent of people are being treated for delusional disorders. We now know that this is the tip of an iceberg. In 2010, Rachel Pechey and Peter Halligan, both at Cardiff University, UK, presented 1000 people with 17 delusion-like beliefs, and asked whether they held them strongly, moderately, weakly or not at all. The beliefs were either relatively mundane, such as “Certain people are out to harm me” and “I am an exceptionally gifted person that others do not recognise”, or more bizarre, including “I am dead and/or do not exist” and “People I know disguise themselves as others to manipulate or influence me”. In all, 39 per cent of participants held at least one of these beliefs strongly, and a whopping 91 per cent held one or more at least weakly. What’s more, three-quarters of people subscribed to bizarre beliefs to at least some extent.

“Symptoms of psychosis-like delusions are just the extreme end of a continuum of similar phenomena in the general population,” says Ryan McKay at Royal Holloway, University of London. More evidence for this comes from the Peters Delusion Inventory, which is frequently used to measure how prone people are to delusional thinking. The inventory asks respondents whether or not they have ever experienced various different beliefs that often crop up in a clinical context, resulting in a delusion-proneness range from 0 to 21 (see “How deluded are you?“). Among the general population, people score an average of 6.7, with no difference between men and women. People with psychotic delusions score about twice this. So they do have more of these beliefs, but what really sets them apart from others is that they tend to be more preoccupied with their delusional beliefs and more distressed by them. “It’s not what you think, it’s the way that you think about it,” says Emmanuelle Peters of King’s College London, who led the development of the inventory.

That we are all prone to delusions may not be so surprising. A range of cognitive biases makes the human mind fertile soil for growing all kinds of irrational beliefs. Confirmation bias, for example, means we ignore inconvenient facts that go against our beliefs and uncritically accept anything that supports them. Desirability bias leaves us prone to shoring up beliefs we have a vested interest in maintaining because they make us or our group look good. Clustering bias refers to our tendency to see phantom patterns in random events, impairing our ability to draw logical conclusions from the available evidence.

A quick trawl of social media is all it takes to see how these utterly human ways of thinking can contribute to a cornucopia of strange and idiosyncratic beliefs. But the question of why some of us are more delusion prone than others is more difficult to answer.

It could have something to do with how we see the world – literally. In one study, volunteers watched an optical illusion consisting of a set of moving dots that could either be perceived as rotating clockwise or anticlockwise. The dots seemed to periodically flip direction, in much the same way a Necker cube changes its orientation as you look at it. Those individuals who scored highly on delusion-proneness perceived the dots as switching direction more frequently, suggesting they have a less stable perceptual experience. How this influences thinking remains unclear, but it doesn’t end there. Participants then wore glasses, which they were told would make the dots appear to rotate one way rather than the other. In reality, the glasses had no effect, but delusion-prone people reported seeing the dots move in the supposed biased direction – a case of seeing what you believe. Another recent study revealed that their perception of time is distorted, too. Delusion-prone people were more likely to believe they had predicted events they could not have because of the order they happened in, indicating that they were making mistakes in judging the temporal order of their thoughts.

It is tempting to conclude that people susceptible to delusional thinking are more suggestible than others, but another study designed to test this explicitly found the opposite. In fact, delusions don’t typically start out as an idea seeded by someone else, but from a strange or anomalous experience generated by ourselves. The crucial second step in forming a delusion is that the person then invents an explanation for this experience. People with Capgras delusion, for example, explain a disturbing feeling of disconnection from a loved one by concluding that he or she has been replaced by a doppelgänger or hyper-realistic robot. This implies some kind of problem with evaluating the plausibility of one’s beliefs, says McKay. In Capgras, it has been linked to damage in specific brain networks. However, there is a more everyday reason that people hold implausible beliefs: a tendency to jump to conclusions on the basis of limited evidence.

“Do you ever feel that things in magazines were written especially for you?”

The extent to which anyone does this can be measured with a simple experiment. Imagine two jars containing a mix of black and orange beads: one contains 85 per cent black beads and 15 per cent orange, and the other has the reverse proportions. You select a bead from one, without knowing which it is. Let’s say the bead is orange. You are then asked whether you would like to make a call on which jar you are taking beads from, or whether you want to draw another bead to help work it out. It is prudent to examine a few beads at least – it is quite possible to draw two orange beads from a jar with mostly black, and vice versa. Yet, around 70 per cent of people being treated for a delusion make a judgement after seeing just one or two beads. Only 10 per cent of the general population are as quick to jump to conclusions, but the more prone you are to delusional thinking, the fewer beads you are likely to sample before making your decision.

This jumping-to-conclusions bias might seem stupid, but it isn’t a sign of low intelligence, according to clinical psychologist Philippa Garety at King’s College London. Instead, she believes it reflects the kind of reasoning an individual favours. Some of us rely more on intuitive thinking – so-called system one thinking – while others are more likely to engage slower, analytic “system two thinking”, which is needed for reviewing and revising beliefs. In a recent study, Garety’s team found that the less analytical a person’s style of thinking, the fewer beads they wanted to see before making a judgement. “It’s not that people with a jumping-to-conclusions bias don’t understand or can’t use evidence,” she says. “They’re just overusing system one at the expense of system two.” And sure enough, Garety’s latest study confirms that these intuitive thinkers are also more prone to clinical delusions.


It looks like a vulnerability to delusions is part and parcel of regular human psychology. After all, everyone is an intuitive thinker at times: even people who favour system two thinking rely on quick, system one thinking when tired, stressed or scared. Whether humanity is becoming more deluded than ever is another question. In today’s hyper-mediated world, we are continually exposed to new experiences and people, and called upon to evaluate all sorts of beliefs that our forebears wouldn’t have encountered. We may also be more tired and stressed. As a result, it is possible we have more numerous or richer delusions than past generations. Nobody has done the research. But even if that is the case, this may have some advantages. “Delusions can be helpful when they make people feel good about themselves or explain aspects of their life that are difficult to understand,” says Bortolotti. It can be empowering to feel that a celebrity is in love with you, for example. And there is plenty of evidence that an inflated belief in your talents can have all sorts of benefits, from success in job interviews to attracting a sexual partner.

Alternatively, our alarming susceptibility to fake news and the outlandish behaviour of key players on the world stage might lead you to conclude that we could do with a bit less delusional thinking. If so, the good news is that insights into delusion psychology point to some ways we can curb it. Garety has helped design an intervention to train people’s slow-thinking skills. SlowMo, which includes therapy and an app, is intended for people with paranoid delusions, but it nurtures mental habits all of us can benefit from. They include gathering sufficient data before making conclusions, learning to question your initial thoughts and impressions about events, and considering different explanations of experiences. SlowMo is currently being tested. If it proves effective, the app will be available in the UK through the National Health Service.

Changing your mind
Of course, changing the way you think isn’t easy. It takes effort, and support. “There’s some evidence that people who have good relationships at home and have someone to talk to are more able to activate slow thinking,” says Garety. Even if that’s not your goal, sharing your thoughts is a good first step to dispelling delusions. “It’s psychologically healthy to recognise that our thoughts sometimes need inspection and engagement with the world to assess how right they are,” says clinical psychologist Daniel Freeman at the University of Oxford.

Simply talking can highlight delusional thoughts in ourselves and others. But then what? We know that delusions are impervious to counterargument. In fact, trying to disprove them can backfire. Freeman has some advice based on his clinical work. First, provide a plausible, non-threatening alternative perspective. Then, help the deluded person gain evidence that bolsters this perspective.

“We don’t try to disprove people’s beliefs,” he says, “because we know that has the opposite effect, just like when people argue in a pub – no one changes their mind.” If you don’t believe him, ask any Jesus Christ.


Strange Beliefs

Despite being diverse and idiosyncratic, delusions cluster into a few core themes.

Persecutory Delusions: beliefs that others are out to harm you. This is the most common type of delusion, affecting between 10 and 15 per cent of people.

Referential Delusions: beliefs that things happening in the world – from news headlines to song lyrics – relate directly to you. Persecutory and referential delusions often go hand in hand.

Control Delusions: beliefs that your thoughts or behaviours are being manipulated by outside agents. Such delusions are common in schizophrenia.

Erotomanic Delusions: beliefs that someone who you don’t know, typically a celebrity, is in love with you.

Grandiose Delusions: unfounded beliefs that you are exceptionally talented, insightful or otherwise better than the hoi polloi.

Jealous Delusions: irrational beliefs that your partner is being unfaithful. This is the type of delusion most commonly associated with violence.

Somatic Delusions: erroneous beliefs about the body. In Ekbom’s syndrome, people believe they are infested with parasites. People with Cotard delusion believe they are dead or don’t exist.

Misidentification Delusions: beliefs about changed identity. A classic is Capgras delusion, where people believe that a loved one has been replaced by a doppelgänger.


How Deluded Are You?

Almost everyone is vulnerable to delusions, but some of us more than others. These 21 questions constitute the Peters Delusion Inventory, which is the most widely used measure of delusion proneness. Give yourself one point for each “yes” and zero points for each “no”, then tot up your score.

1 Do you ever feel as if people seem to drop hints about you or say things with a double meaning?

2 Do you ever feel as if things in magazines or on TV were written especially for you?

3 Do you ever feel as if some people are not what they seem to be?

4 Do you ever feel as if you are being persecuted in some way?

5 Do you ever feel as if there is a conspiracy against you?

6 Do you ever feel as if you are, or destined to be someone very important?

7 Do you ever feel that you are a very special or unusual person?

8 Do you ever feel that you are especially close to God?

9 Do you ever think people can communicate telepathically?

10 Do you ever feel as if electrical devices such as computers can influence the way you think?

11 Do you ever feel as if you have been chosen by God in some way?

12 Do you believe in the power of witchcraft, voodoo or the occult?

13 Are you often worried that your partner may be unfaithful?

14 Do you ever feel that you have sinned more than the average person?

15 Do you ever feel that people look at you oddly because of your appearance?

16 Do you ever feel as if you had no thoughts in your head at all?

17 Do you ever feel as if the world is about to end?

18 Do your thoughts ever feel alien to you in some way?

19 Have your thoughts ever been so vivid that you were worried other people would hear them?

20 Do you ever feel as if your own thoughts were being echoed back to you?

21 Do you ever feel as if you are a robot or zombie without a will of your own?



0-5 You are less prone to delusions than most. Your thinking style is probably more analytical than intuitive.
6-7 Congratulations! You are normal. The average score is 6.7, with no difference between men and women.
8-21 You are more prone to delusions than most. You are likely to think intuitively and jump to conclusions.

Schizophrenia Bulletin

This article appeared in print under the headline “Delusional you”

Article amended on 24 November 2017
We corrected the scoring of the Peters Delusion Inventory questionnaire