When learning new words, 7.5-month-old infants remember both the qualities of an actual word and the aspects of the voice speaking it, according to a new study in theJournal of Experimental Psychology: Human Perception and Performance (Vol. 29, No. 6).
In a study of 24 infants, Indiana University cognitive psychologist Derek Houston, PhD, in collaboration with the late Peter Jusczyk, a professor of psychology at Johns Hopkins University, found that infants could remember words one day after initially hearing them.
They inferred the infants' level of word recognition through a head-turn preference procedure.
In the procedure, a red light captured the attention of an infant, and then a recorded voice read words in the context of short sentences. A day after the training session, the words were read again, this time in the context of new sentences. Researchers inferred that infants recognized a word based on the length of time they looked at the light.
They found that the infants remembered the newly taught words on the second day because the infants looked longer at a red light paired with the newly learned words than with brand new words. Houston also found that infants paid more attention to words when they were read by the same voice that originally taught the word.
That finding, explains Houston, suggests that 7.5-month-old infants may encode information that's irrelevant to understanding words, such as intonation, speaking rate and volume. This information, though it interferes with an infant's ability to generalize word recognition across speakers, could aid infants in word recall at this early developmental stage, he adds.
"Recognizing words across different talkers is not a trivial accomplishment," says Houston. However, infants rapidly learn to do it. By 10.5 months, infants can recognize words spoken by many different speakers, and around a year old, children are actually starting to produce words on their own, Houston notes.
"We are really tapping into a very early stage of word recognition, and a very interesting stage," he says. These infants might not know yet what to really pay attention to, as they are encoding all the details of a speaker's voice, he adds.