Penn study rethinks how children learn first words

Baby Talk

Proceedings of the National Academy of Sciences

Associative theory experiments (below) don't resemble the real world.

A team of Penn psychologists is helping to overturn the dominant theory of how children learn their first words. The research, conducted by postdoctoral fellow Tamara Nicol Medina and professors John Trueswell and Lila Gleitman in the School of Arts and Sciences, suggests that learning occurs more in moments of insight than gradually through repeated exposure.

Current thinking suggests that children track words they hear with things they see. Over time, they narrow down what common element a particular word refers to.

“This sounds very plausible until you see what the real world is like,” Gleitman says.

Experiments justifying the current theory use a limited number of possible word-object associations, whereas real world contexts have an almost infinite amount of associations.

A small set of psychologists and linguists, including members of the Penn team, have long argued that the sheer number of statistical comparisons necessary to learn words this way is simply beyond the capabilities of human memory. 

To demonstrate this, the Penn team conducted three related experiments, all involving short videos of parents interacting with their children. Subjects, both adults and preschool-aged children, watched these videos with the sound muted, except for an audio cue that sounded when the parent said a particular word. The subjects were asked to guess what that word was.

The first experiment was designed to determine how informative the vignettes were in terms of connecting the target word to its meaning. If more than half of the subjects could correctly guess the target word, it was deemed “High Informative,” or HI. If less than a third could, the vignette was deemed “Low Informative,” or LI. Of the 288 vignettes, 7 percent were rated HI and 90 percent were rated LI, demonstrating that even for highly frequent words, determining the meaning of a word simply from its visual context was quite difficult.

The second experiment involved showing subjects a series of vignettes with multiple target words. By asking the subjects to guess the target word after each vignette, the researchers could get a sense of whether their understanding was cumulative or occurred in a “eureka” moment.

The evidence pointed strongly to the latter. Repeated exposure to a target word did not improve accuracy over time. Moreover, it was only when subjects saw an HI vignette first did the accuracy of their final guesses improve.

“It's as though you know when there is good evidence, you make something like an insightful conjecture,” Gleitman says.

The third experiment showed that the inability to forget incorrect meanings is likely necessary for word acquisition. After a delay of a couple days, subjects saw vignettes for words they missed before and showed no evidence of retaining their incorrect assumptions.

“It’s the failure of memory that’s rescuing you from remaining wrong for the rest of your life,” Gleitman says. 

Future work by members of the Penn team will investigate what makes certain interactions more or less informative, as well as the order in which people process visual information in their environment. Both avenues of research could help rewrite textbooks and parenting guides, suggesting that rich interactions with children—and patience—are more important than abstract picture books and drilling.

Originally published on May 26, 2011