Follow the rules, baby.

Viewers of the movie Look Who's Talking hear the thoughts of a wisecracking baby who aims fully grammatical barbs at everything from loaded diapers to dimwitted adults. If real-life infants do the same, they're not telling. They have, however, given scientists a peek at how infants begin to make sense of all the gabbing that goes on around them.

Seven-month-old babies discern and remember simple rules for arranging speech sounds, an ability that may foster language acquisition, according to a report in the Jan. 1 SCIENCE.

In experiments directed by psychologist Gary F. Marcus of New York University, 7-month-olds developed an awareness of predictable patterns in three-syllable nonsense sequences that they heard.

Infants first listened to examples of a sequence in which two different syllables precede a repeat of the initial one. These included "ga ti ga" and "ni la ni." They then heard more versions of that sequence, such as "wo fe wo," and new sequences in which the second sound is repeated, such as "wo fe fe."

Babies looked much longer in the direction from which the sounds of a novel sequence came, reflecting surprise and curiosity about unexpected sound patterns. This reaction indicates that the tots had learned the rule that the first and third sounds are the same, the researchers contend.

Further trials showed that infants did not simply like the sound pattern of some sequences more than others or focus on particular syllables that occurred together more often in one sequence than another. Youngsters also distinguished between patterns such as "de ko ko" and "ji ji we," indicating that their insights were not based on whether sequences did or did not contain an adjacent pair of repeated sounds.

Other investigators have found that 8-month-olds detect the statistical tendency of certain spoken syllables to occur together (SN: 5/3/97, p. 276). They suspect that the ability to notice and generalize statistical regularities in speech ushers kids into the realm of rule-based grammar. Research on connectionist computer systems, which use simple arrays of processing units to learn past tenses of verbs and other linguistic conventions, has bolstered the notion that rule use emerges from statistical learning.

Marcus' findings lend support to the contrasting view that prewired brain circuits regulate grammar learning. A connectionist computer system devised by Marcus failed to recognize syllable sequences as the babies had done.

Yet using a different connectionist system, psychologist Jeffrey L. Elman of the University of California, San Diego says he has successfully simulated Marcus' infant findings. Grammar skills may indeed grow out of babies' recognition of statistical patterns in the talk that they hear, Elman proposes.