Cognitive Daily reports nearly every day on fascinating peer-reviewed developments in cognition from the most respected scientists in the field.
Greta Munger is Associate Professor of Psychology at Davidson College whose works include The History of Psychology: Fundamental Questions. Dave Munger is a writer whose works include Researching Online and The Pocket Reader. And yes, he is married to Greta.
The Stroop Effect was originally just a language effect: we're slower identifying the color text is printed in when the words themselves name different colors. In the 81 years since the effect was first observed, it's been applied to a variety of very different phenomena. In general, the effect is explained by automatic processing: when a process is automatic, it conflicts with the desired goal and so slows processing. In fact, the Stroop Effect is so robust that researchers now use it to determine if a process is indeed automatic.
Much research has focused on the issue of whether racial bias is automatic, but a team led by Jerzy Karylowski wanted to know if racial categorization itself is automatic, so they turned to the Stroop task. Would you be slower to identify the color a person's name is printed in if it conflicts with their race, regardless of your racial bias?
The Stroop Effect is one of the most-studied phenomena in psychology. The test is easy to administer, and works in a variety of contexts. The simplest way to see how it works is just to look the following two lists. Don't read them, instead say the color each word is displayed in, as quickly as you can:
If English is your native language, you should be much quicker at naming the colors of the first list than the second list. Why? Even though the task is to identify the colors, proficient readers can't stop themselves from reading the words, which slows color identification in cases where the color is different from the word.
But recently, Amir Raz and colleagues noticed that they could reduce and even eliminate the Stroop Effect by hypnotizing participants and suggesting to them that the words were in a foreign language, so they could focus solely on color. In a new experiment, Raz and three other researchers attempted to see if the hypnosis itself was necessary.
A Witches' Bible states that "the sensitive is psychically aware of character qualities, or emotional or spiritual states, in the subject, and this awareness presents itself to him or her as visual phenomena." It's easy to dismiss such claims as pseudoscientific claptrap, yet there exist humans who, when presented with nonvisual stimuli such as tastes or smells, perceive visual imagery. I'm talking about the scientifically recognized condition, synesthesia. Synesthetes are people who perceive stimuli presented in one mode (often corresponding to one of the five senses) with a different mode. For example, musical tones might also be perceived as colors, or a friend might appear to have blue lips (as rendered in the photo of my son Jim at left).
Might it also be possible for a synesthete to associate emotions with visual images? British psychologist Jamie Ward believes he has found an individual (a nineteen-year-old woman whose initials are GW) with just such a condition. GW says she perceives "auras" around the faces of certain people, and when she sees or hears some words, she perceives colors (the same color always associated with the same word), which occupy her entire field of vision.
But how does Ward know GW isn't just fabricating the entire story?
All this talk about stereotypes can get you thinking. Perhaps some stereotypes reflect actual differences. Take color vision, for example: men often refer to themselves as "color-impaired," letting the women in their lives make home design decisions and even asking them to match clothing for them. Maybe they're just behaving in accordance with traditional stereotypes ... but maybe there's something more to it.
In the 1980s, vision researchers began to find some real physical differences between the eyes of many women and those of most men. "Normal" color vision is possible because we have three different types of cone cells in our eyes, each of which responds to a different wavelength of light. The process is basically the reverse of how a TV set or computer monitor works: on a TV, there are three different colored dots—red, green, and blue—and the millions of "colors" we see are based on mixtures of different proportions of those colors. In the eye, cone cells can have three different photopigments. These are usually generalized as red, green, and blue, but their actual values are closer to yellowish green, green, and bluish violet. To avoid confusion, psychologists typically refer to them to long-, medium, and short-wavelength sensitive cones. Supposing we're looking at a yellowish-green thing, the long-wavelength cones are stimulated the most, the medium-wavelength cones are stimulated a bit, and the short-wavelength cones are not stimulated at all, and the appropriate signal is sent along the optic nerve to the brain, which then recognizes the color as "yellowish-green."
What the researchers were finding when they actually looked at the structure of the eye is that many women—perhaps over fifty percent—possessed a fourth photopigment. Was this merely a genetic anomaly? Would the brain even be able to process this fourth input? The early research suggested that it would not. Women were no better at determining whether two very similar color patches were actually the same. They were only slightly better than men at detecting subtle spots of red light, a fact researchers attributed to individual difference.
However, Kimberly Jameson, Susan Highnote, and Linda Wasserman were not convinced by this evidence. Five- and six-year-old girls are better at naming colors than boys, and grown men are not as good at color-naming compared to women. They felt the existing measures of color sensitivity and color-matching did not capture all the differences between men and women, and devised a new experiment that they felt was more representative of real-world vision.
It's quite difficult to examine an eye to determine if it has the fourth photopigment—the process generally involves removing the eye itself. Jameson and her colleagues might have had just a bit of difficulty recruiting volunteers to participate in an experiment requiring such extreme measures, so instead they used a genetic test to determine how many different photopigments participants were likely to possess (they estimate this process to be about 90 percent accurate—biologists will recognize this as the genotype versus phenotype problem). Of 64 participants in the study, 23 were women with 4 photopigments, 15 were women with 3 photopigments, 22 were men with 3 photopigments, and 4 were men with 2 photopigments (this is commonly called "color-blindness," but most people with 2 photopigments can still distinguish between many colors).
Next, participants viewed a spectrum projected on a lucite window covered with tracing paper. Over the next hour and a half, they performed an array of tasks, including marking the edges of the visible rainbow, marking the locations of the "best example" of each of the major colors, and marking the edges of each "band" of color in the rainbow. Between each task, a camera flash was set off to mask the previous spectrum example, and the experimenter mounted a new sheet of tracing paper on the panel.
The most compelling results came from the number of spectral bands task:
Type of participant
Average number of spectral bands
Number of participants
Four-pigment females
10
23
Three-pigment females
7.6
15
Three-pigment males and females
7.3
37
Two-pigment males
5.3
4
Four-pigment females perceived significantly more bands of color than both three-pigment males and females. Further, three-pigment males and females are statistically indistinguishable, suggesting that the result is not due to some cultural difference between men and women.
So why were others unable to find significant results in a color-matching task when we see such dramatic results here? Jameson et al. suggest that there may be two (or more) different modes of seeing color, each processed differently in the brain. The brain may use the data from all four photopigments for some processes, but not for others. But this is still supposition. What's clear from this study is that the stereotype of women being better with color may reflect real differences between men and women.
Jameson, K. A., Highnote, S. M., & Wasserman, L. M. (2001). Richer color experience in observers with multiple opsin genes. Psychonomic bulletin and review, 8, 244-261.
When I was about twelve years old, I came up with an idea for a massive practical joke to play on an unsuspecting baby. For its entire childhood, everyone around the baby would conspire to convince it that the sky was green. Then at some point in the future, perhaps in front of the entire sixth grade class at Whitworth Elementary School, the truth would be revealed, and one poor kid's world would be turned upside-down.
Somehow I was never able to recruit enough people to pull this ruse off, but it does beg the question: would such a joke even be possible, or would our natural perceptual categories outweigh the influence of hundreds of tricksters? In short, do children understand the differences between colors first, or do they simply learn the names for colors without understanding what they signify? While they were probably not inspired by an idea for a practical joke, Nicola Pitchford and Kathy Mullen of McGill University were able to devise an experiment to begin to address the question ("The Development of Conceptual Colour Categories in Pre-School Children: Influence of Perceptual Categorization," Visual Cognition, 2003).
A large body of research has shown that adults categorize colors into eleven basic categories: white, black, red, green, yellow, blue, brown, purple, pink, orange, and grey. These categories have been tested extensively, even across cultures, and found to be readily identifiable by all adults. When asked to name colors across a wide spectrum of possibilities, most people use the basic color categories to describe even the colors that fall on the border between two categories.
Young children also learn these categories, but only gradually. A very young child might use the same name—say, blue—to describe a wide variety of colors (in fact, two of the 2-year-olds that Pitchford and Mullen studied used "blue" to describe all 11 colors in their study).
Pitchford and Mullen asked kids ranging from age 2 to 5 to name the color of the outfit a cartoon character was wearing. Not surprisingly, the older kids were more accurate, but most interesting was the type of errors the children made. Colors can be arranged in a color wheel (or more accurately, a three-dimensional solid). Some colors, such as orange and yellow, are closer neighbors on the color wheel than others, such as blue and red. The researchers analyzed the errors kids made naming colors and came up with the following result:
Children were sorted by language ability. Those with the ability of an average 2-year-old made the most color errors—but they made an equal number of errors for colors that were distant on the color wheel compared to adjacent colors. It's as if they simply randomly selected a color when they weren't sure about its name. By contrast, the 3-year-old language group, when they made errors, were more likely to pick adjacent colors—saying "yellow" when the color was orange, for example. While the 4-5 group was even more accurate, the few mistakes they made tended to be naming adjacent colors (the distinction between grey and brown is the most difficult, and errors are even made by some adults).
So it seems that toddlers, while able to learn the names of some colors, haven't yet developed an understanding of the relationship between colors. By the time they are three, kids have learned most of the basic colors, but they have also learned more about how the colors relate to each other. Older kids still make some mistakes, but nearly all of them are in related colors, so they're almost always in the ballpark of the correct color.
I suspect this means that my 6th-grade prank would have stopped working long before its victim even entered elementary school. Aspiring pranksters, be warned: better to stick with water balloons and dribble glasses than mess with the human perceptual system.
How do we see things in color? How do we know objects stay the same color when the color of the light they reflect changes as the lighting changes? We see this effect most dramatically in the theater, where the stage lights cover every color of the rainbow, yet we still know the heroine is wearing a purple dress and our hero has majestic blonde hair.
In today's reading ("Surface-Illuminant Ambiguity and Color Constancy: Effects of Scene Complexity and Depth Cues" by James M. Kraft, Shannon I. Maloney, and David H. Brainard of UC-Santa Barbara [Perception, 2002]), the authors explore some of the implications of this issue.
The problem of color vision is very complex—so complex that there's certainly no way I can explain it in a single blog post. Nonetheless, much of how we perceive color is well understood. What I'll be discussing here is a second-order problem. Seeing color is one thing, but adjusting for different lighting conditions—color constancy—is yet another. Somehow, we're able to acheive color constancy without even thinking about it. But how? Do we unconsciously detect the type of lighting in a particular scene and then adjust accordingly? This seems unlikely; otherwise the art of photography wouldn't be difficult at all: we'd all intuit how to adjust our cameras to different lighting conditions and take good pictures. Yet the proponderance of ghastly orange photos murking up cheesy family websites and dust-covered-photo albums suggests we possess no such intuition.
Kraft et al. suggest that we might use the other objects in our field of view to help us determine the accurate color of another object. For example, if we see two people in a poorly illuminated room, we could compare the person we know (say, Jenna Bush) with someone we don't (her new boyfriend, Henry Hagar) and conclude that Henry has dark hair and pinkish skin, simply by comparing what we know with what we don't know.
Kraft and his colleagues designed an experiment using a simpler setting: a "room" made of cardboard, with a gray patch on the wall whose color could be changed by adjusting a spotlight focused precisely on the patch. Theater lights were used to vary the overall lighting in the room, and then observers were asked to change the lighting on the gray patch so it looked "perfectly gray." Later, the same observers were asked to do the same task in a more "complex" scene (the same room, but with a couple extra objects added: a board covered with patches of varying colors and textures, and a tall rectangular cardboard column). They suspected that the "complex" scene would help observers maintain color constancy—with many other cues to help them see how the room was lit, they would be better able to recognize a "truly" gray object. You can see their "room" here.
What they found surprised them. Observers were no better at attaining color constancy in a "simple" room than they were in a "complex" room. Perhaps even the simple room was complex enough to help observers attain color constancy. They tried a different tack: they showed viewers the same rooms, but added additional "invalid cues"—they lit some parts of the room differently in order to confuse observers. In this case, observers were better at maintaining color constancy in the "complex" room, suggesting that complexity helps us attain color constancy in confusing lighting situations.
In short, we're very good at determining the color of objects in most situations. We probably wouldn't need to see Jenna next to Henry to know he has dark hair. It's only when things get really confusing that we must resort to crutches to help us accurately see color. It may also explain why it's so difficult to portray "confusion" in a theater. When there's supposed to be something like a storm or a battle on stage, the actors have to rely on the audience to use its imagination and suspend disbelief. Our perceptual system is simply too good to be fooled that easily.
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Cognitive Daily reports nearly every day on fascinating peer-reviewed developments in cognition from the most respected scientists in the field.
A Witches' Bible states that "the sensitive is psychically aware of character qualities, or emotional or spiritual states, in the subject, and this awareness presents itself to him or her as visual phenomena." It's easy to dismiss such claims as pseudoscientific claptrap, yet there exist humans who, when presented with nonvisual stimuli such as tastes or smells, perceive visual imagery. I'm talking about the scientifically recognized condition, synesthesia. Synesthetes are people who perceive stimuli presented in one mode (often corresponding to one of the five senses) with a different mode. For example, musical tones might also be perceived as colors, or a friend might appear to have blue lips (as rendered in the photo of my son Jim at left).
