Scientists from Birkbeck College, London, have used the Geodesic Sensor Net to show that a baby's brain goes through a crucial stage of development between six and eight months of age, allowing them to "see" a well-known optical illusion.
The skullcap is loaded with electrical sensors for detecting brain-waves that might tell doctors whether a baby is suffering from a hidden psychological illness, such as autism, which may develop in the future.
When adults are shown "pacman" shapes arranged with their "mouths" open in four corners, their brains automatically register a square, even though the shape itself does not actually exist.
Babies younger than six months are unaware of the square, yet at eight months they have acquired the cerebral "software" to register the four corners and so "see" a four-sided shape.
A team led by Gergely Csibra, a psychologist, used the sensor net to show in a study published in the journal Science that this stage of development is accompanied by the emission of certain brain-waves called gamma oscillations.
The electrical activity of the brains of babies younger than six months does not include gamma oscillations, but by eight months they can be registered when the brain is performing the task of identifying an object from its constituent shapes.
"This new work not only tells us that babies as young as eight months recognise complex objects in the same way as an adult does, but also allows us to think of new studies into early infant development," said Dr Csibra.
"The difference between six and eight-month-old babies is also intriguing and may show that there is an important development in how the brain organises information from the outside world at that age."