Four year olds are rational

Young Children Make Good Scientists: Even 4-year-olds are able to use evidence to change their beliefs about how the world works by Alison Gopnik. Excerpts:

"Over the past 15 years, my lab and others have shown that, to a surprising extent, even very young children reason in this way. The conventional wisdom is that young children are irrational. They might stubbornly cling to their beliefs, no matter how much evidence they get to the contrary, or they might be irrationally prone to change their minds—flitting from one idea to the next regardless of the facts.

In a new study in the journal Child Development, my student Katie Kimura and I tested whether, on the contrary, children can actually change their beliefs rationally. We showed 4-year-old children a group of machines that lit up when you put blocks on them. Each machine had a plaque on the front with a colored shape on it. First, children saw that the machine would light up if you put a block on it that was the same color as the plaque, no matter what shape it was. A red block would activate a red machine, a blue block would make a blue machine go and so on. Children were actually quite good at learning this color rule: If you showed them a new yellow machine, they would choose a yellow block to make it go.

But then, without telling the children, we changed the rule so that the shape rather than the color made the machine go. Some children saw the machine work on the color rule four times and then saw one example of the shape rule. They held on to their first belief and stubbornly continued to pick the block with the same color as the machine.

But other children saw the opposite pattern—just one example of the color rule, followed by four examples of the shape rule. Those children rationally switched to the shape rule: If the plaque showed a red square, they would choose a blue square rather than a red circle to make the machine go. In other words, the children acted like good scientists. If there was more evidence for their current belief they held on to it, but if there was more evidence against it then they switched."

"A new paper in PNAS by Gordon Pennycook and David Rand at Yale shows that ordinary people are surprisingly good at rating how trustworthy sources of information are, regardless of ideology. The authors suggest that social media algorithms could incorporate these trust ratings, which would help us to use our inborn rationality to make better decisions in a complicated world."