Awash in streams of adult chatter, babies fish out and recognize some of their first words thanks to well-timed touches from their caregivers, a new study suggests.
An experimenter’s synchronized taps on an elbow or knee enabled 4-month-olds to notice nonsense words embedded in spoken strings of syllables, say psycholinguist Amanda Seidl of Purdue University in West Lafayette, Ind., and her colleagues. Timed touches from parents and other adults as they say the names of body parts may explain how babies tune in to words such as feet and tummy months before recognizing other nouns, the scientists propose April 16 in Developmental Science.
“Caregivers’ touch cues may play a key role in infants’ ability to recognize body part words so early, and these words could provide a toehold for learning other early nouns,” Seidl says.
Touch has largely been overlooked as a sense needed by babies for the daunting task of deciphering words as adults talk.
Infants selectively respond to people’s names, such as mommy, early on, but names appear to be special cases: Adults frequently say names to babies without using any other words. What’s more, a word such as mommy is often enunciated with an attention-grabbing melody.
In contrast, words referring to various types of objects cascade out of adults’ mouths amid a torrent of verbs and modifiers. In the last couple of years, evidence has suggested that infants nonetheless start to recognize words for foods and body parts by age 6 months.
When presented with pairs of pictures, 6- to 9-month-olds typically looked at the one depicting a food or body part — such as a banana or hand — just named by their mothers, psychologists Elika Bergelson of the University of Rochester in New York and Daniel Swingley of the University of Pennsylvania in Philadelphia reported in 2012.
Infants probably use a variety of acoustic cues to pick words out of adults’ utterances, including pauses and intonation changes, Bergelson says. Seidl’s results add tactile cues to this mix, she remarks. “Given that touches from adults are frequent and can be tracked by young babies, touch is a good candidate for helping babies break into the speech stream.”
In the new study, 24 4-month-olds were held by their mothers as a recording played of a woman speaking a string of 27 nonsense syllables that could be subdivided into nine fake words, each consisting of three consecutive syllables. The syllable string repeated 24 times, lasting five minutes and 45 seconds.
A female experimenter touched each child on a single body part, such as a knee, each time a specific set of three consecutive syllables, corresponding to a word, played. The experimenter also touched the youngster on another body part, such as an elbow, just once during the 24 repeats of the recording for each of the eight other words made of three-syllable combinations.
Afterward, babies spent substantially less time looking toward speakers playing the word that had always elicited touches than looking toward speakers emitting words linked with one touch or new words composed of three syllables that appeared in the recording but not consecutively.
Seidl interprets this result as an indication that 4-month-olds had familiarized themselves enough with words associated with consistent touches by an adult to be more intrigued or surprised by other three-syllable mixes.
In a trial with 24 more 4-month-olds and the same recording, a female experimenter touched her own knee or chin each time a particular three-syllable word played and touched her own elbow or eyebrow once for every other simulated word in the recording. Babies who watched that act showed no preference for any word type afterward.
Receiving consistently timed touches from caregivers critically helps infants to identify these words, Seidl concludes. Preliminary data from her lab suggest that mothers touch their babies on the appropriate spot within one second of saying words for body parts.