Variation Helps Toddlers Learn Words Faster
You probably know the old story about the three blind men and the elephant: One man grabs the tail and thinks an elephant is like a rope; one wraps his arms around a leg and things the animal is like a tree; the third touches the elephant's flapping ear and concludes it is a giant fan. The fable is often used to underscore differences in perspective, but as it turns out, children may learn words for objects a bit like the blind men and the elephant.
A new University of Iowa study published in this month's Psychological Science found that toddlers who play with similar but distinct objects learn words faster than students who play only with similar objects.
A research team at the University of Iowa, taught 16 18-month-old babies a dozen different categories of objects, either using very similar or fairly different sets of objects as examples. After a month of training, all of the toddlers studied could differentiate objects by shape, a typical developmental stage called "shape bias." However, toddlers allowed to play with variable toys learned on average about 10 new words a week as measured by a standard list of developmentally appropriate vocabulary words, such as names of furniture, food and vehicles. By comparison, normal 18-month-olds, and the toddlers playing with only similar objects, learned on average four words a week.
To get an idea of what's going on, picture two 18-month-olds, each playing with a set of bowls, while adults are talking about and repeating the names of the objects. One youngster has a matched set of cereal bowls like you'd pick up at the market, all blue plastic of medium size. The other child has a red plastic cereal bowl, a large metal mixing bowl, and a tiny plush toy bowl. The toddler who hears "bowl" used to name each of the diverse items learns more quickly that the word is associated with a shape and a function, not a material, a color or a size, and may also start to understand that different objects may be grouped according to different characteristics, like material.
Lead author Lynn K. Perry, a University of Iowa psychology doctoral student, and her colleagues found that toddlers who experienced varied examples of objects developed not just shape bias but materials bias. When exposed to new objects, they could categorize them by shape or material, and they more quickly learned new categories of objects as well as new words.
"It really was surprising how far the difference led; it cascaded to how well they learned those categories and novel categories and new words," Ms. Perry told me, even though the new words came from new categories, not simply words like "red" or "heavy" that might describe the original categories.
By contrast, the toddlers exposed only to similar objects became over-focused on the shape differentiation. In a follow-up experiment, the researchers made up a new shape out of hair gel and named it a nonsense word. Then they asked the child to point out another object of the same kind, showing one of a similar shape made out of shaving foam and another of a different shape out of gel. Toddlers exposed to similar objects could only distinguish based on shape, not substance.
The findings suggest, Ms. Perry said, that drilling children on a single set of flashcards or examples may be less effective in teaching toddlers words than giving them a broad experience.
"When teaching a new concept or a new word, it might be better to teach it through several different ways or examples or toys," she said. "It looks like the variety helps them learn that concept sooner and maybe understand other concepts, too. So don't just use one example over and over."
Even very young children, it seems, may be able to understand how an elephant is like a tree, and a rope, and a fan — if they get to experience all of those things.