Babies may thrive on wordless conversation.

At 4 months of age, babies are at a loss for words. They're not at a loss for conversational skills, though.

A new study finds that 4-month-olds engage in precisely timed vocal interactions with adults. By this age, the researchers report, most babies have learned when to make sounds to a partner, when to pause and for how long, when to join in with a partner, and how to take turns vocalizing. In other words, they exhibit the same patterns of rhythmic give-and-take that adults use to converse.

Moreover, the extent to which an infant at this age coordinates sounds and silences with his or her mother and strangers has major implications for social and intellectual development by 1 year of age, reports a team led by psychiatrist Jerome Jaffe of Columbia University.

"More vocal coordination between an infant and an adult is not necessarily better," Jaffe says. His research appears in the current MONOGRAPHS OF THE SOCIETY FOR RESEARCH IN CHILD DEVELOPMENT (vol. 66, no. 2).

For example, 4-month-olds who coordinated vocalizations to a moderate extent' with both their mothers and with strangers exhibited considerable emotional and social ease in laboratory situations at age 1. These emotionally secure infants communicate flexibly by using a modest amount of conversational coordination, the researchers theorize.

In contrast, infants who displayed either the loosest or tightest vocal coordination with both their mothers and with strangers exhibited emotional and social problems at age 1. Jaffe proposes that these youngsters had learned either to stay out of nonverbal conversations as part of a larger tendency to shrink from interactions with adults or to ease anxiety associated with such conversations by rigidly timing their vocal rhythms.

A different pattern of nonverbal dialogue heralded intellectual advances. Babies who had tightly coordinated their vocalizations with those of a stranger in a laboratory scored particularly well on standard intelligence tests at age 1. This type of response among 4-month-olds reflects curiosity about novel situations, the scientists hold. Other researchers have linked this curiosity to high intelligence scores in later years.

Jaffe's group studied vocal interactions of 88 infants during brief play periods with their mothers and with an experimenter. Interactions with each adult took place in both the child's home and in a laboratory. A computerized system analyzed the timing and pattern of vocalizations during each encounter.

The researchers used conversational acts--such as turn taking, interruptions, and pauses at the point of turn exchanges--to calculate the degree to which the partners' behaviors were correlated.

The group later tested the 1-year-olds for social and emotional ease by briefly separating the children from their mothers and introducing an adult stranger. Intelligence tests consisted of tasks such as using toy blocks to build designs demonstrated by an adult.

Jaffe's results flesh out longstanding theories that babies somehow time nonverbal interactions in useful ways, comments psychologist Edward Z. Tronick of Children's Hospital in Boston.

"Infants may have an innate capacity for interactive timing that flexibly responds to the social context," Tronick says.

The new findings support the view that people at all ages learn to perceive and reason about the world primarily through dialogues rather than as isolated thinkers, remarks psychologist Phillippe Rochat of Emory University in Atlanta. However, he suspects that learning during the first months of life, rather than an innate capacity, enables infants to time their vocal responses.

"Language is not a prerequisite for children to experience the basic benefit of conversing with others," Rochat says.