Most babies begin to recognize themselves in mirrors when they are about a year and a half old. This type of self-recognition is an important developmental milestone, and now scientists at the University of Texas at Austin have discovered a key factor in this: tactile experiences.
Their new study found that babies who were asked to touch their faces developed self-recognition earlier than those who didn’t. The research was published this month in the journal. Current biology.
“This suggests that babies who pull their toes or tap their fingers are not simply playing,” said Jeffrey Lockman, a professor of human development and family sciences at UT and senior author of the paper. “They are developing self-awareness through self-directed activities. I believe this work demonstrates a possible mechanism by which self-recognition can develop based on the active experience that human babies naturally generate.”
The researchers began by placing small vibrating discs on the foreheads and cheeks of toddlers when they were about 14 months old, before the usual age at which self-recognition occurs. In response to the vibration, the children raised their hands and touched the record. The researchers then put the children in front of a mirror and watched them reach out to touch the discs.
The researchers then had the children perform the standard mirror mark test for self-recognition in which a small mark of paint or makeup was placed on each child’s face. If the child looked in the mirror and touched the mark on his face or said words like his name or “I,” he demonstrated self-recognition.
The researchers also looked at a control group of children who were exposed to the laboratory experience with mirrors but not vibrating discs. Both groups were comparable at the beginning of the study and observed monthly until they were recognized or reached 21 months.
Children who touched their faces more frequently recognized themselves in the mirror about two months earlier, on average, than when children typically begin to recognize themselves in a mirror.
The study challenges a long-standing assumption that self-recognition in early childhood is somehow programmed. Scientists long believed that early mirror recognition was an inherent function of the human brain and those of our closest primate relatives, rather than being linked to sensory or motor experiences.
The researchers said the findings may have implications for interventions in children with delays in motor development.
“Interventions for babies who have problems related to motor skills typically focus on reaching and manipulating objects in the external world,” Lockman said. “These findings suggest that reaching out to the body may be equally important and that exploring the body is the gateway to self-knowledge.”
Lisa Chinn of the University of Houston and Claire F. Noonan and Katarina S. Patton of Tulane University also authored the paper. Funding for the research was provided by the National Institutes of Health.