The moon landing and climate change are hoaxes, vaccines cause autism, 9/11 was a set-up, and our minds are secretly being controlled with chemtrails in the sky.
Is scepticism toward these kinds of unfounded beliefs simply a matter of intelligence?
Not according to new research.
"We show that reasonable scepticism about various conspiracy theories and paranormal phenomena does not only require a relatively high cognitive ability, but also strong motivation to be rational," said study leader Assistant Professor Tomas Stahl, a social psychologist of the University of Illinois at Chicago.
"When the motivation to form your beliefs based on logic and evidence is not there, people with high cognitive ability are just as likely to believe in conspiracies and paranormal phenomena as people with lower cognitive ability."
Earlier research indicated that people with higher cognitive ability — or a more analytic thinking style — were less inclined to believe in conspiracies and the paranormal.
The new studies, based on online surveys with more than 300 respondents each, looked closer.
One survey found that an analytic cognitive style was associated with weaker paranormal beliefs, conspiracy beliefs and conspiracy mentality.
However, this was only the case among participants who strongly valued forming their beliefs based on logic and evidence.
Among participants who did not strongly value a reliance on logic and evidence, having an analytic cognitive style was not associated with weaker belief in the paranormal or in various conspiracy theories.
In the second survey, the researchers examined whether these effects were uniquely attributable to having an analytic cognitive style or whether they were explained by more general individual differences in cognitive ability.
Results were more consistent with a general cognitive ability account.
The researchers noted that, despite a century of better educational opportunities and increased intelligence scores in the US population, unfounded beliefs remained pervasive in contemporary society.
"Our findings suggest that part of the reason may be that many people do not view it as sufficiently important to form their beliefs on rational grounds," Stahl said.
From linking vaccines with autism to climate change scepticism, these widespread conspiracy theories and other unfounded beliefs can lead to harmful behaviour, he said.
"Many of these beliefs can, unfortunately, have detrimental consequences for individuals' health choices, as well as for society as a whole."
How do we hang on to old memories?
Elephants are widely known for their incredible memories - but humans don't do so badly, either, when it comes to recall.
Scientists have just reported fascinating findings around long-term memorisation, and why we are somehow able to remember things that are not emotionally charged and have only been seen or experienced a few times in the past.
French researchers decided to challenge the memory of individuals they had tested in the laboratory a decade previously, discovering that participants recognised images seen for only a few seconds 10 years earlier.
It has been difficult for scientists to account for key factors involved in memorisation.
Yet it was known that frequent exposure to sensory data translated into durable memories - and that something seen or experienced only once might never be forgotten when strong emotions are involved.
Researchers at the Brain and Cognition Research Centre in Toulouse were able to control for these variables — and evaluate another type of memorisation.
They asked 24 people tested in the laboratory 10 years previously to return for new tests.
A decade earlier, the same individuals had been shown a sequence of simple clip-art images, each for only a few seconds, without being given any particular instructions to memorise them.
When they returned to the lab in 2016, they were asked to identify these pictures presented in pairs alongside new images.
On average, those surveyed obtained 55 per cent correct answers, compared with 57 per cent in the case of images already seen at least three times and up to 70 per cent for some participants.
Under these experimental conditions, it seemed that three exposures were sufficient to memorise an image for 10 years.
Although scientists have known for several years that memories can be retained implicitly — that is, without being able to consciously access them — the new study showed they could directly influence participants' choices, and may sometimes even provoke a strong feeling of familiarity.
The researchers are now seeking to clarify the biological basis for this, hypothesising the such memories rely on a small group of ultra-specialised neurons in our brains.