Conscious memories may emerge in infants.

Sometime in the first year of life, babies develop a flair for maintaining relatively durable memories of simple events that they can recall intentionally, a new study finds. The investigation raises new questions about why people typically forget all about their infancy.

It also adds to an ongoing debate about whether memory derives from one or many brain systems.

"This is the first solid evidence that infants consciously remember what they have learned," asserts Laraine McDonough, a psychologist at the University of California, San Diego. "But our data don't address whether infants consciously remember where and when they learned the same information."

She and her coworkers present their data in the Aug. 1 Proceedings of the National Academy of Sciences and an upcoming Journal of Experimental Child Psychology.

Before looking at memory in infants, the team examined "deferred imitation" of experimentally demonstrated tasks in eight healthy adults, three adults with frontal-lobe damage that largely spared memory, and seven adults with brain damage that blocked much of their ability to recall new information for more than a few minutes.

Volunteers concentrated on a series of word lists read by a researcher. In between these tasks, they watched the experimenter perform specific actions. These consisted of causal chains of events (such as turning on a hair dryer, placing a balloon in its air stream, and moving the balloon by tilting the dryer) and arbitrarily ordered events (for example, folding and unfolding a piece of paper, cutting off its corners, and drawing a star on it).

The next day, the researchers showed the same sets of objects to the volunteers and asked them first to handle the objects as they wished, then to imitate the researcher's earlier actions.

Healthy participants and those with frontal-lobe damage correctly imitated most of the previously viewed actions, even when doing what they wished with the objects, McDonough's group reports. The other brain-damaged patients recalled far less and performed on a par with seven healthy adults given the objects without having seen the demonstrations.

Successful deferred imitation relies on brain structures essential for declarative memory, the capacity for intentionally calling to mind specific facts and events, McDonough argues. Amnesia-inducing brain damage affects these structures, she theorizes, but not those needed for procedural memory, which handles skills and knowledge employed without conscious effort.

The second study shows that babies also imitate actions after long delays and thus display declarative memory, according to McDonough. She and San Diego coworker Jean M. Mandler conducted a study in which 12 babies, all 11 months old, observed a researcher performing simple actions. These included causal sequences (such as making a rattle by putting a button in a box and shaking it) and arbitrary sequences (say, putting a bracelet on a teddy bear and brushing the bear).

When shown the sets of objects 1 day later and 3 months later, infants accurately imitated the causal sequences but largely forgot the arbitrary sequences.

"These data reflect deferred imitation by 11-month-olds, but it's very difficult to know if this is conscious remembering in infants," asserts Carolyn Rovee-Collier of Rutgers University in New Brunswick, N.J.

Moreover, the work with amnesia patients probably revealed more about memory's decline than its development, Rovee-Collier holds, since all subjects exceeded 55 years of age.

Rovee-Collier theorizes that a single memory system renders infants sensitive to cues in their surroundings that trigger recall (SN: 4/18/92, p.244).

McDonough responds that Rovee-Collier studies only procedural forms of memory in infants. The loss by adulthood of declarative memories from infancy may stem partly from the massive pruning of brain connections that normally occurs during childhood, she suggests.