Babies mav thrive on wordless conversation At 4 months of age, babies are at a loss

for words. They’re not at a loss for con- versational skills, though.

A new study finds that 4-month-olds en- gage 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 pat- terns of rhythmic give-and-take that adults use to converse.

Moreover, the extent to which an infant at this age coordinates sounds and si- lences with his or her mother and strangers has major implications for so- cial and intellectual development by l year of age, reports a team led by psychia- trist Jerome Jaffe of Columbia University

“More vocal coordination between an infant and an adult is not necessarily bet- ter,” Jaffe says. His research appears in the current MONOGRAPHS OF THE SOCIETY FOR RE- SEARCH IN CHILD DEVELOPMENT (vol. 66, no. 2).

For example, Cmonth-olds who coordi-

Chemists decorate nanotubes for usefulness In a step that could lead to harder ma-

terials and tinier electronic devices, researchers have found a promising new way to attach molecules to carbon nanotubes.

In its simplest form, a carbon nanotube is a one-atom-thick sheet of carbon curved in- to a cylinder. Such tubes exhibit extraordi- nary strength and electrical conductivity. For many potential uses of carbon nan- otubes, chemists need to attach clusters of atoms, called functional groups, to the out- sides of the tubes. The new report, which will appear in an upcoming issue of the JOLR- NAL OF THE AMEIUCAN CHEMICAL S o c m , demon- strates a novel way to do just that.

A variety of tests by the Rice re- searchers revealed that the functional groups indeed attach to the carbon nan- otubes. Using a scanning tunneling mi- croscope, Paul Weiss of Pennsylvania State University in University Park has al- so confirmed that. He now is further characterizing the nanotubes.

“I think that [such] functionalization of the nanotubes is very important, be- cause there is a whole host of applica- tions,” comments Robert Haddon of the University of California, Riverside.

For example, nanotubes carrying cer- tain functional groups could mix more readily with other materials. Scientists

ton. The process can attach a A transmission electron microscope image shows a functional group to as many as simple carbon nanotube k smooth edges (left). A 1 out of every 20 carbons on a similar nanotube has bumpy edges after groups of nanotube. which can contain atoms bind to it (right). millions of carbon atoms.

Tour and his colleagues used a tech- nique similar to one by which chemists link functional groups to graphite, which forms from flat sheets of carbon. The Rice researchers attached an electrode to apply a voltage to a mesh of carbon nanotubes known as bucky paper. Then, to link each type of chemical group to the nanotubes, they bathed the bucky paper in a solution containing a different aryl diazonium salt.

Each molecule of an aryl diazonium salt contains a six-carbon ring, to which the researchers had attached one of a variety of functional groups. Joined to one of the ring’s five other carbon atoms was a different chemical group that the scientists expected would readily get knocked off as the molecule approached the charged bucky paper. If that hap- pened, the ring’s suddenly available car- bon atom would bond to a carbon of the nearby nanotube.

then might be able to create new conduc- tive plastics or even plastics that are as hard as steel. The Rice group now is working to make carbon nanotubes com- patible with the epoxy resins used by NASA on spacecraft, Tour says.

Another exciting vision would use car- bon nanotubes for making electronic cir- cuits that are far tinier than today’s silicon- based circuitry. Doing so will require chemically hooking carbon nanotubes to other microscopic electronic components, comments Weiss.

In fact, one of the functional groups that the Rice researchers successfully at- tached to carbon nanotubes has exhibit- ed both memory and switching behaviors necessary for electronic devices, says Tour. The researchers are investigating whether a nanotube and its functional groups retain their desirable strength, conductivity, and chemical traits after they’re combined. --J: Corman

nated vocalizations to a moderate extent with both their mothers and with strangers exhibited considerable emo- tional and social ease in laboratory situa- tions at age 1. These emotionally secure infants communicate flexibly by using a modest amount of conversational coor- dination, the researchers theorize.

In contrast, infants who displayed ei- ther the loosest or tightest vocal coordi- nation 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 anxi- ety associated with such conversations by rigidly timing their vocal rhythms.

A different pattern of nonverbal dia- logue heralded intellectual advances. Ba- bies 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 Bmonth-olds re flects curiosity about novel situations, the scientists hold. Other researchers have linked this curiosity to high intelli- gence scores in later years.

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

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

The group later tested the l-year-olds for social and emotional ease by briefly separating the children from their moth- ers and introducing an adult stranger. In- telligence tests consisted of tasks such as using toy blocks to build designs demon- strated by an adult.

Jaffe’s results flesh out longstanding theories that babies somehow time non- verbal interactions in useful ways, com- ments 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 ca- pacity, enables infants to time their vocal responses.

“Language is not a prerequisite for chil- dren to experience the basic benefit of conversing with others,” Rochat says.

-B. Bower

390 SCIENCE NEWS, VOL. 159 JUNE 23,2001