Child's 'mental number line' affects memory for numbers

The University of Oklahoma study suggested that the way kids visualise numbers reflects their understanding of what the symbols mean.

When children in Western cultures first learn numbers, they place them on number lines from left to right. But the placement is uneven: smaller numbers are spaced farther apart than larger numbers, which are crunched up toward the end of the line.

Gradually, this placement evens out, corresponding with the child's understanding of what the numbers mean, said Clarissa Thompson, co-author of the study.

"Young children's knowledge sometimes seems impressive, because they can count, 'one, two, three, four, five, six, seven, eight, nine, ten,' but often they just learn by rote," Thompson was quoted as saying by LiveScience.

"Their counting doesn't have much to do with their understanding of how big the numbers are."

To find out how number-line visualisation relates to understanding of numbers, the researchers gave a group of children a stack of blank number lines with "0" written on the left end and "20" on the right end.

Each child heard a series of numbers from one through 19 and had to mark on the number line where they thought that number belonged.

Next, the children were told a story that included a few numbers. After the story, the researchers threw off the kids' memories by asking them to name four cartoon characters. Then they asked questions about the story, like "How many forks did Colleen wash?" Children with a more linear number line were better at remembering the numbers in the story.

In three experiments, the researchers found that the more even a child's number line, the better the child was at remembering numbers.

This was true for preschoolers for numbers from one to 20 and for elementary school children for numbers from one to 1,000.

"We really do live in a world of numbers," Thompson said. Some we only need to approximate, and others we need to remember exactly. Ability to estimate the sizes of numbers influences the ability to remember the numbers exactly."

The findings are published in the journal Psychological Science.