Expert Comment: How to build a ghost
Friday 31st Oct 2025, 1.39pm
The reason why ghosts, witches, and zombies are so appealing to us is because they violate our early developing expectations about the world in highly predictable ways. There is a simple formula for creating the scary creatures that come out at Halloween. We all know the formula but most of us don’t know how we know it.
Here’s how the magic happens.
When we were babies – long before we’d had a chance to observe very much about the physics of the world around us – we already expected unsupported objects to fall earthwards, to move in continuous paths, and not to pass through other solid objects. These expectations concern the basic physics of the world around us and form part our evolved psychological toolkit for navigating the world.
When we were babies – long before we’d had a chance to observe very much about the physics of the world around us – we already expected unsupported objects to fall earthwards, to move in continuous paths, and not to pass through other solid objects. These expectations concern the basic physics of the world around us and form part our evolved psychological toolkit for navigating the world.
A little bit later in childhood – around three or four years old – we start to appreciate that other people have beliefs and desires, that they can hold both true and false representations of the world, that they can be deceived and that they, in turn, can tell us lies.
All this may sound rather abstract, but it’s all you need to know if you want to build a ghost.
To create a simple ghost concept, all you have to do is imagine a perfectly normal physical agent but then ascribe to it some counterintuitive properties – such as the ability to defy gravity by floating upwards or being able to pass through solid walls.
Psychologists describe such constructs as ‘Minimally Counter-Intuitive’ or MCI for short. They are minimal in the sense that they typically involve just one or two small violations of our innate intuitions – just enough to be attention-grabbing, memorable, and catchy but not so counterintuitive as to leave us confused.
A little bit later in childhood – around three or four years old we start to appreciate that other people have beliefs and desires, that they can hold both true and false representations of the world, that they can be deceived and that they, in turn, can tell us lies.
As a result, simple ghost concepts have been documented all around the world but not beliefs in beings that only exist on Wednesdays or can only communicate through calculus.
And MCI concepts are big business.
Take Santa. He is presented to us as a regular humanlike agent in all respects except that he can magically pass through narrow passages – such as chimneys. So he violates the intuitive principle of object solidity. Santa and his reindeer also have the magical power of flight. So he also violates the principle of intuitive gravity. Santa also violates our ‘theory of mind’ expectations, by magically knowing whether we’ve been naughty or nice, presumably by monitoring the thoughts and behaviours of all children around the world at the same time.
This socially salient MCI feature may well be one of the clinchers that helps to explain not only why children are enchanted but also why adults buy into it.
The truth is that these kinds of ideas – the building blocks of religion and children’s stories alike – are universal.
And Santa, of course, is a huge money spinner – with worldwide expenditure on Christmas exceeding a trillion dollars by some estimates – more than the GDP of most countries.
Halloween ghouls – like Santa and his sleigh – are money-spinners in America but the same kinds of ideas have universal appeal because they tap deep into our evolved psychology. America is a big country but not as big as China. Chinese New Year with its fire-breathing dragons and evil spirits is estimated to be worth around $150 billion per annum. And of course, there are countless other festivals involving MCIs all around the world.
The truth is that these kinds of ideas – the building blocks of religion and children’s stories alike – are universal. We all know how to build a ghost. But now we know how we know.
Harvey Whitehouse is the author of Inheritance: The Evolutionary Origins of the Modern World.
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