Kids as young as 4 innately use sorting algorithms to solve problems

Children as young as 4 years old are capable of finding efficient solutions to complex problems, such as independently inventing sorting algorithms developed by computer scientists. The scientists behind the finding say these skills emerge far earlier than previously thought, and should force a rethink of developmental psychology.

Experiments carried out by Swiss psychologist Jean Piaget and widely popularised in the 1960s asked children to physically sort a collection of sticks into length order, a task Piaget called seriation. His tests revealed until around age 7, children applied no structured strategies; they approached the problem in messy ways through trial and error.

But new research by Huiwen Alex Yang and his colleagues at University of California, Berkeley, shows a minority of even 4-year-old children can develop algorithmic solutions to the same task, and by 5 years old more than a quarter are capable of the same thing.

“Maybe we weren’t giving children enough credit,” says Yang. “We need to dig a little deeper at what children are actually doing, their reasoning ability.”

In the experiment, the team asked 123 children aged 4 to 9 to sort a series of digital images of bunnies into height order. Initially, they were able to see the bunnies in a group and compare their heights directly, and all the children were able to order them correctly with relative ease.

But later, the heights of all bunnies were obscured and the only way to compare them was to select two at a time. When selected, the children were told whether the bunnies were already in the right order or if they were in the wrong order, in which case the bunnies were switched automatically after being viewed. This forced the children to come up with a new strategy for ordering them without being able to see the whole group at once.

The researchers looked for evidence of the children applying known solutions, scouring their sequence of comparisons for evidence of the use of existing algorithms. The team found overall, the children still performed far above chance – indeed, they independently discovered at least two efficient algorithmic solutions to the sorting problem developed by the field of computer science: selection sort and shaker sort.

In 34 per cent of tests, children used a sequence of comparisons that suggested they employed – at least for a time – a known sorting algorithm. In 110 tests out of the total 667 carried out, children used selection sort, and in 141 tests they used shaker sort. In a further 21 tests they used a combination of the two algorithms. A total of 67 of the 123 children used at least one identifiable algorithm, and 30 of the children used both strategies at different points in the experiment.

But the number of children using an algorithm to solve the tasks was certainly linked to age. Only 2.9 per cent of 4-year-olds used an identifiable algorithm, while that rose to 25.5 per cent for 5-year-olds and 30.7 for 6-year-olds. By age 9, more than 54 per cent of children were using an identifiable algorithm.

“There’s a long history of overturning Piaget,” says Andrew Bremner at the University of Birmingham in the UK. Bremner says he views Piaget as a genius who revolutionised developmental psychology and set out the stages children go through when learning about the world, but admits he “wasn’t a fantastic experimentalist” and he often designed poor tests without proper controls. “People have set about pointing out that children could do things that he said they couldn’t do, a lot younger.”

Essentially, in recent decades it has been gradually shown Piaget had the right idea about childhood development, but was slightly pessimistic about the ages at which children passed through the process. And this new research adds to that weight of evidence. But interestingly, it focuses on seriation, which Bremner says was one of the last remaining and most stubborn of Piaget’s experiments to be found to apply to younger children than previously thought.

“The children can demonstrate success at this task in this particular context much earlier than we would predict,” says Bremner. “So they don’t just approach the world as a kind of blank slate, but they apply strategic approaches to the ways in which they try to solve problems.”

Sam Wass at the University of East London, UK, says Piaget believed children needed to build a thorough understanding of complex systems before they could develop strategies to work with them, but that this is increasingly seen as unnecessary.

“This research is part of a great wave in psychology that challenges the idea that, in order to generate behaviours that look complex, you have to have complex thoughts and understanding underpinning them,” says Wass. “In fact, as this study shows, you can produce behaviours that look complex based on a much more parsimonious set of rules.”