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How do we perceive a rainbow? And does everyone perceive a rainbow in the same way? These seemingly simple questions can reveal some interesting features of the human brain. For instance, is the “striped” appearance of the rainbow—the seven distinct bands of color that we see—a construct of our higher mental processes, or do the mechanics of human color vision determine it at a very early perceptual level? If your language does not have separate words for “blue” and “green” (and many languages, including Welsh, do not), do you perceive these shades as more similar than a speaker of English?
Searching for answers to these questions, in recent years many scientists have concluded that speakers of languages that label color in ways distinct from those used in English may see a different rainbow from that of English speakers. Recent studies have claimed that language processing is automatically involved in perceptual decisions about color in the brains of adults, even when hues are visible only briefly (100 milliseconds) or when decisions do not require participants to name colors verbally. Moreover, these effects are language-specific, so speakers of Russian or Korean show a different pattern of responses to color than speakers of English.
A recent study in PNAS by researchers at the University of Surrey challenges this view, however. It suggests an intriguing and novel account of color categorization in infants. In this study 18 English-speaking adults and 13 four-month-old infants were shown a colored target on a colored background. Adults were faster to initiate eye-movements toward the target when the target and background colors came from different color categories (for example, blue target, green background) than when both target and background were the same color (such as different shades of blue).
How Babies See Color
This discrimination advantage for different-category compared to same-category judgments is called Categorical Perception (CP). It is now clear that the effect in adults is language-driven. For instance, healthy, right-handed adults only show CP selectively when colors are presented to the right visual field. It is generally accepted that CP occurs because colors presented to the right visual field preferentially access language-processing areas located in the left hemisphere.
The authors of the new article agree with the current general consensus that CP in adults depends on privileged access to language areas in the left hemisphere. They also agree that the precise color terms that are represented in language are culturally transmitted during childhood and that there has been no “nativist,” or innate, pre-linguistic partitioning by the visual processing pathways into innate color categories in the left hemisphere. This idea fits with their data demonstrating that four-month-old infants showed no hint of CP when targets were presented in the right visual field. Because these infants have not yet acquired language, it is unsurprising that they do not show language-driven category effects in the left hemisphere.
So far, so predictable. What is striking, however, is that the same four-month-old infants did show a CP effect in the right hemisphere, exactly the reverse of the effect shown by adults. When a green target appeared on a green background in the left visual field (which has preferential access to the right hemisphere), infants were significantly slower to move their eyes toward the target than when a blue target appeared on the same green background. The authors claim that their results provide some evidence for pre-linguistic partitioning of color categories in four-month-old infants, but only from stimuli that preferentially access the right hemisphere. Such a result provides some empirical evidence for the existence of an innate pre-linguistic category boundary between blue and green.
If infants show an initial innate organization of color into precise categories in the right hemisphere of the brain, does such organization persist into adulthood? The answer to this question appears to be, “no, it does not.” Even when the dominant left-hemisphere system is suppressed by a concurrent task that prevents access to verbal codes in the left hemisphere, (see here and here, or cannot be reached in split-brain patients—people who have had the connection severed between their two hemispheres⎯no trace of categorical organization in the right hemisphere remains. If the present results are really evidence of some pre-linguistic, and possibly innate categorical organization in the right hemisphere, the pre-linguistic system is not merely overshadowed in the process of language learning. Rather, it is completely obliterated. In this case, the power of language to shape our cognitive categories must be enormously strong, and Whorf’s controversial views about the relationship between language and thought would appear to have been vindicated.
Future Questions
Yet there are several reasons to be cautious about such an interpretation of the present results. If an innate organization of color categories were present in all humans before language categories are learned, we might expect to find it in our nearest primate relatives as well. A recent study of baboons has shown this not to be the case, however.
A number of methodological features make the new findings hard to interpret. Because of the difficulties of carrying out eye-tracking studies with infants, the data came from only half of the 26 infants that they tested. The colors used for adults were too difficult for infants to discriminate, so the researchers chose a set of just three widely separated colors for the infant testing. These comprised two targets (one green and one blue) and a background color that was just on the green side of the boundary between green and blue. As a result, there is a larger “perceptual distance” between the blue target and the green background than between the green target and the green background. This greater distinction might be enough to produce differences in the discriminability of the two targets. No direct comparison with adults can be made to investigate this confounding factor between perceptual distance and color category, because the adults in the study saw a different set of colors.
A small difference in discriminability might affect responses only in the right hemisphere for several reasons. In terms of the organization of the infant brain, integration of the two hemispheres is generally not complete before two years of age, so little transfer of information from one hemisphere to the other would be expected at four months. The visual system develops asynchronously across hemispheres, with right hemisphere development preceding left in most humans. In addition, processing of visual information for color and location may not be fully integrated before 26 weeks, due to the earlier maturation of the parvocellular visual stream, relative to magnocellular stream. (The parvocellular visual stream is better at perceiving color and fine details.) The readiness of the two hemispheres to respond to a second stimulus, after exposure to an attention-grabbing stimulus presented in central fixation also differs in young infants. All these factors might contribute to greater sensitivity to a small difference in the discriminability of target and background in the right hemisphere compared with the left.
The present results deal only with a single category boundary, that between green and blue, so more evidence would be required to infer a complete set of pre-partitioned color categories in the right hemisphere of infants. More research is also needed to discover what the situation would be for infants born to speakers of the many documented languages that use a single term to describe all those shades that an English speaker would call green and blue.
In conclusion, the new data present a most interesting challenge to researchers in the field but, given the significance of the theoretical consequences of such a powerful relation between language and thought, much wider investigation of the issues seems called for. It is to be hoped that the new findings will act as a spur to other infant labs to join and broaden the investigation of these fascinating phenomena.
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9 Comments
Add CommentReason to be cautious indeed - it's not at all clear what is being tested here, the ability to discriminate colour, or the ability to categorise a colour. Both. moreover, have a considerable degree of subjectiveness; the ability to discriminate colour must depend on the quality of the subject's eyesight and ambient conditions (light intensity, quality etc), and the ability to categorise a colour must depend on the subject's experiences.
Reply | Report Abuse | Link to thisAnother reason for caution is the researchers' conflation of color categorization with color experience. Infants may track (or categorize) colors differently than adults, but that doesn't necessarily imply their experiences are different. Another way of putting the point is that the word 'see' is ambiguous here between unconscious and conscious seeing.
Reply | Report Abuse | Link to this"The authors of the new article agree with the current general consensus that...."
Reply | Report Abuse | Link to thisThere's a general consensus that the word "redundant" needs to be returned to this writer's language skills.
This is really all very simple.... The brain:- initially in less than 200 milliseconds,via the vestibulo-autonomic areas, and then via the many cerebral links, responds to visual inputs the same way it responds to auditory, olfactory, touch etc.
Reply | Report Abuse | Link to thisIt is the association between the different areas that results in LEARNING.. as described by Pavlov (1910-1917 Lectures conditioned reflexes, Orienting (focusing) response, reflex of purpose and reflex of freedom) and by Edward de Bono (1969 Mechanism of Mind).
Modern neuro- physiologists and psychologists are merely identifying the various components of the above associative pathways.
Unfortunately the mid brain component is so dense and small that is is very difficult to observe/examine, compared to cerebral areas with fMRI and magnetoencephalograms.
Pavlov and de Bono are still the masters of the over view and whole body function models; where others pretend that by isolating and defining one component/pathway explains the whole!
B McKay
When learning Spanish in Ecuador, I was confused when people told me my eyes were blue, not blue. It took me weeks to realize that Ecuadorians differentiate blue (azul) and light blue (celeste) much the way English speakers differentiate red and pink. Just as we might tell someone a dress is pink, not red, they would explain to me that my eyes were not blue but light blue. We think of pink and red as distinctly different colors because our language differentiates them, but they're both shades of the same color, aren't they? So it's easy for me to understand why infants don't process or see colors the way adults do until after taught to do so.
Reply | Report Abuse | Link to thisThank you for your comments. The authors of the post, Rick Hanley and Debi Roberson, have asked me to post their replies to these comments. I've broken up their replies into three sections:
Reply | Report Abuse | Link to thisPost 2
'rObward' is correct to point out that there is a fundamental difference
between color categorization and color discrimination. This can be seen
from the fact that adults can discriminate between approximately two
million different shades of color even though there are only eleven basic
color categories in English.
As far as ambient conditions are concerned, it is usual to test in darkness
when using computer-generated colors with the screen as the only source of
light. The authors report that the co-ordinates of the colors that they
presented were measured with an appropriate colorimeter, so ambient
conditions should have been the same for all infants.
yesight could not be
Reply | Report Abuse | Link to thisformally tested, of course, but those infants whose data was used (13/26)
moved their eyes to at least 2 targets in each condition, so they were able
to discriminate differences both within- and across the adult category
boundary between blue and green. The claim that we evaluated in this
article is that there is evidence for the existence of adult color
categories in infants at only four months of age. The authors argue for an
innate category boundary because those infants initiated eye movements
faster when the target came from a different color category to distractors.
We ourselves are not yet convinced that this evidence is robust.
Consequently we agree with rObward that the ability to categorise a colour
depends on experience (we would claim linguistic experience). Nevertheless
we consider this to be an issue that deserves further experimental
investigation. We have made a broader summary of research in the field in a
chapter in a forthcoming book: "Words and the world: How words capture
human experience". A draft of this paper is available to download from our
websites.
We agree with 'dorsalstream' that color categorization and color experience
Reply | Report Abuse | Link to thisare not the same thing. For example, a speaker of English will claim that a
patch of color that is green and a patch of color that is blue belong to
different color categories. Speakers of Himba (a language that does not
have separate words for blue and green) will claim that these two patches
belong to the same color category. It does not follow that the color
experiences of the Himba and English speaker are different. It is
perfectly possible that identical color experiences are categorized in
different ways by speakers of different languages and by infants and adults.
Post 6
A similar distinction applies in Russian between Sinij (dark blue) and
Goluboj (light blue). Italian actually has three color terms that cover
what speakers of English would call blue: Azzurro (turquoise), Celeste (sky
blue) and Blu (dark blue). We agree with kcathyb that these distinctions
are learned. However we don't agree with her that pink and red (or Sinij
and Goluboy) are two words for what is 'the same color'. For speakers of
languages that make these distinctions, these are genuinely different
colors. In our opinion, unless they are physically identical, two things
are the 'same color' only as a result of linguistic convention.
As a young child (speaking English) I was aware that the adults around me would often call certain colors that appeared differently to me by the same name. This was particularly true of tertiary colors such as yellow-orange, red-orange, yellow-green, blue-violet, etc. The corrections that adults made regarding color perceptions were confusing and seemed wrong, creating a situation that piqued my interest in color. I grew up to be a visual artist, painter and color consultant. For me, the most accurate descriptions of color are usually understood between painters who began their color description with a particular pigment, then describe how that pigment has been modified to create the color in mind. Keep in mind that a large national paint company such as Benjamin Moore or Sherwin Williams has over 300 colors described as "green". When it comes to color, a picture really is worth more than a thousand words.
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