Mind Reading Is Child's Play

By Prashant Nair
ScienceNOW Daily News
19 June 2006

All of us can read minds to some extent thanks to a special class of brain cells known as mirror neurons. When a gardener picks up a hose, for example, we have a pretty good idea that he's going to water the plants with it, even if we've never seen that gardener before. New research suggests that people pick up this knack for prognostication early: Infants start to predict the goals of others' actions at about the same time they learn to perform those general actions themselves.

Researchers first discovered mirror neurons in monkeys in the 1990s. These cells fired when the monkeys saw other monkeys perform goal-oriented tasks such as picking up a piece of fruit to eat. Later, scientists also found the cells in humans, and a study published last year showed that mirror neurons help predict the actions of others (ScienceNOW, 23 February 2005). But researchers weren't clear when the function of these socially essential cells began kicking in.

To nail down a time frame, neuroscientists Terje Falck-Ytter and Claes von Hofsten at Uppsala University in Sweden recruited three groups of subjects: adults, 12-month-olds, and 6-month-old infants. The researchers showed each group a video of an actor's hand moving toys into a bucket nine times. With each repeated viewing, the team measured the amount of time it took the volunteers to look at the bucket. After the first viewing, adults and 12-month olds started gazing at the bucket even before the hand arrived at it, indicating that they knew the intention of the actor. But 6-month olds never looked at the bucket until the actor had placed the toys inside.

It just so happens that the motor skills needed to move an object into a nearby container develop at the age of 7 to 9 months. Thus, mirror neurons may not be fully functional until a person can perform the actions they are supposed to predict, the team reported online yesterday in Nature Neuroscience.

The findings shed new light on the development of mirror neurons, says neurobiologist Luciano Fadiga at the University of Ferrara, Italy, who was the first to find evidence for mirror neurons in humans. Still he cautions that the study may not have been able to detect mirror neuron activity in 6-month-old infants because they didn't understand what they were seeing.