When you tickle the toes of a newborn baby, the experience for them isn’t quite as you would imagine it to be, researchers from Goldsmiths, University of London’s Department of Psychology have found.
Their research - reported in the Cell Press journal Current Biology on October 19 – shows that infants in the first four months of life apparently feel a touch and wiggle their feet without connecting the sensation to you.
“Our findings are really the first to address what is quite a fundamental question about our sensory experience in early life,” said Andrew Bremner, Head of the Department of Psychology. “When young babies feel a touch on their hand, can they appreciate where that touch is in the outside world?”
It appears the answer is no.
Dr Bremner and Jannath Begum Ali made this discovery by showing something that might seem paradoxical at first. When adults cross their hands or feet and someone touches them, they often make mistakes in identifying the origin of the sensation they’ve felt.
The researchers found that six-month-old infants make that mistake too, but four-month-old infants get it right more often. In other words, infants actually outperform older infants and adults in correctly placing where they’ve been touched when their feet are crossed.
“We think [this means] that before around six months of age, human babies perceive touches just on their bodies, and not in the external world,” Bremner said.
“If one tries to imagine what this must be like—it's a bit of a dizzying idea.”
The researchers made the discovery by tickling the crossed and uncrossed feet of four- and six-month-old infants with mechanically delivered vibrations. The younger infants moved the foot that was tickled 70 percent of the time either way. Six-month-olds correctly identified the source of the tickle only 50 percent of the time with their feet crossed—no better than chance.
The new study was inspired by earlier findings showing that congenitally blind adults can localise touches equally well with limbs crossed or uncrossed. Adults who lost their sight after birth, even relatively early in life, do not show the same ability.
The researchers wondered whether young infants with very little visual experience of their bodies might not yet perceive touch in the outside world. And, indeed, it appears they don’t.
“Our argument is that for young babies, touches are just perceived as touches on the body - they're not perceived as being related to what they are seeing or hearing, or perhaps even smelling,” Bremner said. “They're not related to objects perceived in vision. To me this sounds like quite an alien sensory world to live in - the tactile world being quite separate from the other sensory worlds.”
The researchers say they now want to explore how and why infants develop a sense of themselves in the world and what the implications are for infants’ understanding.
Find out more about the Department of Psychology's Infant Lab.