Infant brains develop faster than we thought
Scientists discover that infant brain development occurs years earlier than previously thought.
We perceive faces using the right hemisphere of our brains, a unique ability in humans setting us apart from our primate cousins. We had thought this adaptation developed as we learned to read. However, a new study published in the journal eLife by scientists from the University of Louvain in Belgium, finds babies at four months already recognise faces.
"Just as language is impaired following damage to the brain's left hemisphere, damage to the right hemisphere can impair our ability to distinguish faces. It is critical to understand how this develops."
Bruno Rossion, Principal Investigator. University of Louvain and co-author
Using a cap fitted with electrodes to monitor their brain activity, 15 babies sat in their mothers' laps watching a rapid succession of images lasting only 20 seconds. The images were of 48 faces that differed in viewing angle, color, lighting, and background. Interspersed between the faces were 200 images of animals, plants, and man-made objects.
Each image was viewed for only 166 milliseconds, the same rate used in similar adult studies. Yet in spite of the brevity of each image shown, human faces coincided with a spike in the right hemisphere of the brain in infants wearing the cap. The difference between the right and the left hemispheres was even more pronounced than in the same study done with adults, confounding previous assumptions.
Rossion: "Given the enormous resources devoted to digital face recognition, the babies' brain accomplishment is not trivial. The success of this research method in babies demonstrates that it can be used in all ages to improve our understanding of how we develop the ability to perceive complex images."
Humans far outperform computer algorithms in categorizing images. Faces are seen so often and are so socially important to our development, they are ideal for use in studies determining how we visually categorise objects. A fundamental element of facial recognition is our ability to tell individuals apart by tiny details. Now the authors can use the same study method to refine when our visual agility emerges and changes with age.
Rossion: "Parents and carers are already aware of how quickly babies' brains develop. But, gathering evidence of this had been limited by previous methods used — until now."
Human performance at categorizing natural visual images surpasses automatic algorithms, but how and when this function arises and develops remain unanswered. We recorded scalp electrical brain activity in 4–6 months infants viewing images of objects in their natural background at a rapid rate of 6 images/second (6 Hz). Widely variable face images appearing every 5 stimuli generate an electrophysiological response over the right hemisphere exactly at 1.2 Hz (6 Hz/5). This face-selective response is absent for phase-scrambled images and therefore not due to low-level information. These findings indicate that right lateralized face-selective processes emerge well before reading acquisition in the infant brain, which can perform figure-ground segregation and generalize face-selective responses across changes in size, viewpoint, illumination as well as expression, age and gender. These observations made with a highly sensitive and objective approach open an avenue for clarifying the developmental course of natural image categorization in the human brain.
The paper 'Rapid categorization of natural face images in the infant right hemisphere' can be freely accessed online at http://dx.doi.org/10.7554/eLife.06564. Contents, including text, figures, and data, are free to re-use under a CC BY 4.0 license.
eLife is a unique collaboration between the funders and practitioners of research to improve the way important research is selected, presented, and shared. eLife publishes outstanding works across the life sciences and biomedicine -- from basic biological research to applied, translational, and clinical studies. eLife is supported by the Howard Hughes Medical Institute, the Max Planck Society, and the Wellcome Trust. Learn more at elifesciences.org.
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