Evolution is poorly understood by students and, disturbingly, by many of their science teachers. Although it is part of the compulsory science curriculum in most schools in the UK and the USA, more than a third of people in both countries reject the theory of evolution outright or believe that it is guided by a supreme being.

It is critical that the voting public have a clear understanding of evolution. Adaptation by natural selection, the primary mechanism of evolution, underpins a raft of current social concerns such as antibiotic resistance, the impact of climate change and the relationship between genes and environment. So why, despite formal scientific education, does intelligent design remain so intuitively plausible and evolution so intuitively opaque? And what can we do about it?

Developmental psychologists have identified two cognitive biases in very young children that help to explain the popularity of intelligent design. The first is a belief that species are defined by an internal quality that cannot be changed (psychological essentialism). The second is that all things are designed for a purpose (promiscuous teleology). These biases interact with cultural beliefs such as religion but are just as prevalent in children raised in secular societies. Importantly, these beliefs become increasingly entrenched, making formal scientific instruction more and more difficult as children get older.

Defining essences

Pre-schoolers are committed to the idea that members of a species have an inner, inviolable “essence” that makes them what they are. Four-year-olds have a basic understanding of genetic inheritance: that a calf brought up its entire life by pigs will still moo like a cow and not oink like a pig. Three-year-olds insist that a Labrador that undergoes surgery to look like a Rottwieler is still a Labrador. Two-year-olds predict that a dolphin will breathe air and not water if you first tell them that dolphins are mammals (like dogs) that look like fish.

Psychological essentialism is a powerful learning tool. In the face of all the visual evidence to the contrary, it allows us to easily group Chihuahuas and Great Danes into the same category (dogs). And once we know they are members of a familiar category, all sorts of other information comes for free; that they both bark, eat meat and like to chase postmen.

However, the idea that species are determined by an unchangeable core essence directly contradicts the theory of evolution. A consequence of adaptation by natural selection is that populations within a species gradually adapt from one form to another, as humans and apes evolved from the same ancestor. Psychological essentialism is one of the primary reasons why the theory of evolution is so widely misunderstood by both children and adults.

The teleological function compunction

Teleology is the tendency to explain things in terms of their function rather than what has caused them. Adults do this when talking about artefacts – a chair is FOR sitting on – and body limbs – a hand is FOR manipulating things. Children are ‘promiscuous teleologists’. They go a step further and explain even natural phenomena in terms of their purposes – the bush exists SO THAT hedgehogs can hide in it, lions exist FOR looking at in the zoo.

Not only do they spontaneously produce promiscuous teleological explanations for natural things, they also prefer promiscuous teleological explanations compared to scientific explanations. When asked what is a better explanation for why a rock is pointy, the majority of children under 8 years of age choose the explanation that it is so that animals don’t sit on it, rather than because “bits of stuff piled up over time”. Promiscuous teleology is prevalent in children regardless of how their parents describe the world to them or the religious culture that they are growing up in.

This widespread function compunction is neither outgrown nor fully replaced by formal scientific education. Under speeded conditions, even adults with PhDs in scientific disciplines tend to say that promiscuous teleological explanations like ‘Cows have udders so that farmers can milk them’ are correct. The common-sense bias to believe that everything exists for a purpose underpins the intuitive attractiveness of intelligent design.

Can we overcome these psychological biases?

So how do we override such widespread and tenacious cognitive biases? Deb Kelemen and colleagues at Boston University recently published a promising, child-friendly intervention: illustrated storybooks about natural selection.

When asked how a feature changes in a species, the majority of children below 10 years of age will call on a teleological explanation: the giraffe has a long neck SO THAT it can reach the higher leaves. Having established this, Kelemen presented 5-8 year olds with storybooks about a made-up animal: Pilosas. Over the course of the story the children learn that some Pilosas have long, thin trunks while others have short, thick trunks and that all Pilosas eat bugs. The weather changes and the bugs move underground. Those Pilosas with long thin trunks are still able to reach the bugs but those with short thick trunks are not and they die. Only those Pilosas with long thin trunks survive and have babies, who also have long, thin trunks.

This is a great story for young children because it plays on lots of things that they are naturally interested in: life and death and the reasons why things are the way they are. More than that, the evidence suggests that such stories might help overcome cognitive hurdles to understanding adaptation by natural selection.

After having read the story, all of the children were asked a series of questions about a new animal they had never encountered before. For instance, ‘How did grown up Wilkies go from mostly having short legs many hundreds of years ago to having longer legs today?’ The majority of 5- to 8-year-olds in Kelemen’s study explained this change in terms of adaptation and reproduction, rather than promiscuous teleology. This is the opposite pattern of their responses before reading the story.

Perhaps most excitingly, the learning seems to stick. When the same children were asked a similar question about other unfamiliar animals 3 months later, most of them explained changes over time in terms of adaptation and reproduction rather than teleology.

Should we change the national curriculum (again)?

Evolution is typically taught to students at around 14- to 15-years of age as they prepare for their GCSEs. After persistent lobbying by the British Humanist Association, evolution was included in the British national primary curriculum for the first time last year. From September 2015, students will be taught about evolution from Year 6, at around 10-11 years of age.

Might this still be too late? Kelemen chose 5- to 8-year-olds to test because at this age promiscuous teleology and psychological essentialism are still separate and fragmentary. She argues that by 10 years of age they have coalesced into a coherent theoretical framework that then gets in the way of contradictory scientific explanations and may remain the default, gut reaction, even in adults.

Her storybook works because it provides children with an alternative explanatory framework before these cognitive biases become entrenched. Her findings show that even very young children can understand the basic mechanisms of natural selection and can generalise that analogy to new examples. If part of the reason that intelligent design is so popular is because it seems intuitively correct, might the solution be to disrupt those intuitions very early on? Should we reconsider the national curriculum (yet again) and start teaching evolution even earlier?