A joint group of researchers from Chuo University, Japan Women’s University and Tohoku University has revealed that infants aged between 5 and 7 months hold the representation of color categories in their brain, even before the acquisition of language.
This study is published in the online journal of Proceedings of the National Academy of Sciences.
A long-held theory called Sapir-Wharf hypothesis claims that languages define our perceptions. This theory is widely accepted in various fields of study including psychology, linguistics and anthropology. Color perception is also considered to be subject to this theory, since colors are called by their names in daily communications.
Through numerous studies on the color lexicons of languages in the world, categorical color perception is considered to be strongly affected by language. On the other hand, the similarity of color categories across linguistic and cultural differences is also reported as strong evidence of the universality of color categories. Therefore, whether or not language affects color categories has been a central issue related to how we perceive colors.
This new study reveals that the category of colors can be independent of language, at least in the early stage of development in an infant’s visual system.
Infants 5-7 months old were tested to see if brain activity is different for colors in different categories. The brain activity was measured by a near infrared specrtoscopy technique, which realizes comfortable measurement of brain activity in infants.
The study found that the brain activity increased significantly when the colors of blue and green were alternated, while there was no significant reaction to the alternation of different shades of green. The difference was observed in the occipito-temporal area in both left and right hemispheres.
A similar difference was found in adult participants with no significant lateralization. Since language related cortical areas reside in the left hemisphere in most right-handed adults, the observed brain activity had no direct relation to language processing. In addition, brain activity caused by categorical color differences was not found in the occipital region, which is known to play a significant role in the early stage of visual processing.
These results show that color information is processed through multiple cortical stages in infants, in a way similar to adults. They suggest that the brain activity in reaction to different color categories are represented differently in infants, even before the acquisition of language. They also imply that color categories can develop independent of the acquisition of relevant language.
About this developmental neuroscience research
Source: Ichiro Kuriki – Tohoku University Image Source: Image is credited to the researchers. Original Research:Abstract for “Cortical response to categorical color perception in infants investigated by near-infrared spectroscopy” by Jiale Yang, So Kanazawa, Masami K. Yamaguchi, and Ichiro Kuriki in PNAS. Published online January 4 2016 doi:10.1073/pnas.1512044113
Cortical response to categorical color perception in infants investigated by near-infrared spectroscopy
Perceptual color space is continuous; however, we tend to divide it into only a small number of categories. It is unclear whether categorical color perception is obtained solely through the development of the visual system or whether it is affected by language acquisition. To address this issue, we recruited prelinguistic infants (5- to 7-mo-olds) to measure changes in brain activity in relation to categorical color differences by using near-infrared spectroscopy (NIRS). We presented two sets of geometric figures to infants: One set altered in color between green and blue, and the other set altered between two different shades of green. We found a significant increase in hemodynamic responses during the between-category alternations, but not during the within-category alternations. These differences in hemodynamic response based on categorical relationship were observed only in the bilateral occipitotemporal regions, and not in the occipital region. We confirmed that categorical color differences yield behavioral differences in infants. We also observed comparable hemodynamic responses to categorical color differences in adults. The present study provided the first evidence, to our knowledge, that colors of different categories are represented differently in the visual cortex of prelinguistic infants, which implies that color categories may develop independently before language acquisition.
“Cortical response to categorical color perception in infants investigated by near-infrared spectroscopy” by Jiale Yang, So Kanazawa, Masami K. Yamaguchi, and Ichiro Kuriki in PNAS. Published online January 4 2016 doi:10.1073/pnas.1512044113