28 November 2000
Doors Of Perception Examined
by Kate Melville
For most of us, seeing the world around us is such an effortless process that we tend not to give it a second thought. In fact, our vision reflects an incredibly complex feat of bioengineering that outperforms many computer-based systems.
This process involves grouping together different features of an object to form the whole: nib, barrel and lid form a pen, for example. While it is clear that adults and older children can do this, until now, it has been difficult to determine when and how this vital skill develops in young infants--mainly because they can't tell you whether they see a pen or simply a collection of unrelated elements.
Now, using a brain imaging system known as the Geodesic Sensor Net and a test made up of shapes like the "Pacman" from 1980s computer games, scientists at London's Birkbeck College have shown that eight-month-old babies do indeed bind attributes to form a whole object. Their results are published 24 November 2000 in the journal, Science.
The test involved showing the infants a group of four Pacman shapes collectively known as the Kanizsa Square. When placed with the four "mouths" facing inwards, the Pacmen give the visual illusion of a square, which is not actually there. Previous work in adults has shown that the perception of the square correlates with a burst of brain activity known as gamma oscillation.
When six-month-old babies were shown the square, the characteristic signals were not there. However, when eight-month-old babies were shown the same figure, gamma oscillations were seen.
Lead Science author Gergely Csibra said: "Understanding how an infant brain develops is obviously fascinating and may have implications for the education and care of babies. This new work not only tells us that babies as young as eight months recognise complex objects in the same way an adult does, but also allows us to think of new studies into early infant development.
"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."
In the study, 11 six-month-old and 11 eight-month-old infants were shown either the Kanizsa Square or another collection of Pacman shapes on a computer screen. The brain activation was detected by the Geodesic Sensor Net-which fits over the head like a shower cap and can detect the gamma oscillations if they are present. The Geodesic Sensor Net enables researchers to study the activity in babies brains using a safe and child-friendly method. The device gently rests a number of passive sensors on the child's head, which are able to detect the minute changes in electrical fields which happen as groups of nerve cells are active together in the brain. It is a variation on a method called EEG that has been used routinely in hospitals for several decades.
Mark Johnson, director of the research laboratory said: "This research provides us with a powerful new tool for investigating how babies think when presented with everyday objects, toys or faces. While we have only studied healthy babies so far, it is also possible, but not proven, that we may also be able to study babies which are, unfortunately, not developing typically."