Color perception
dmunger | November 19, 2009How does our visual system decide if something is a face? Some automated face-detecting software uses color as one cue that something is a face. For example Apple's iPhoto has no trouble determining that there are two faces in this color picture:
That's Nora in the back, and her cousin Ginger in front. In this picture, however, iPhoto can't identify a face:
That's a vintage black-and-white photo of Nora and Ginger's grandfather, but the computer can't find any faces in it. Do people, like computers, use color to help decide whether something they see is a face? Humans are excellent at…
dmunger | October 1, 2009The other day, our car wouldn't start and Jim had to ask a neighbor over to help him jump-start it. There was much rushing in and out of the house looking for flashlights and other tools to help get the job done. After the neighbor left, Jim wanted to drive somewhere and couldn't find the keys. Clearly he had just had them because he was working on the car. Where could they be? We searched up and down throughout the house, but we couldn't find them and eventually had to use a spare set.
The next morning as I was getting ready to leave for our school carpool in our other car, I found them…
dmunger | June 30, 2009New parents can come up with a seemingly endless array of vexing questions about their infants, from the best brand of stroller to the ideal song to sing them to sleep. The questions begin well before the child is born: what type of clothing should you purchase? What kind of crib?
One question Greta and I dwelled on quite extensively when Jim was an infant was color. We were renting an apartment and couldn't paint the nursery, so we wondered about the color of the toys we bought and the blankets and other bedding for the crib. Would a purple outfit be appreciated? What about a multi-colored…
dmunger | February 25, 2009What is so mesmerizing about pointillist paintings like Seurat's Sunday Afternoon at La Grande Jatte? At first, we're impressed by the technical virtuosity of the work. It's an immense painting that Greta and I visited many times when we were in college in Chicago (and now, whenever we return for a visit):
As you can see even in this reduced image, the painting is composed of tiny dots. But what you may not notice is that the dots in a given region of the painting aren't all the same color. Take a look at this detail:
The leaves in the trees range from red to yellow to green to blue, and…
dmunger | December 30, 2008[This entry was originally posted in April 2007]
The Beck effect is difficult to replicate online, because it involves testing reaction times. However, I think I've figured out a way to approximate the effect. This movie (Quicktime required) will show you how it works. Just follow the directions on the opening screen:
Now, which letter did you see first? Let's make this a poll:
If we manage to replicate the effect, there should be a bias in the results, which I'll explain below so everyone has a chance to try it out before learning the "answer."
In the 1960s, Jacob Beck found that when…
dmunger | August 4, 2008[Originally posted in May, 2007]
"I just didn't see him" is a claim that's repeated over and over in accident reports. Drivers earnestly claim that they simply didn't notice the bicycle/pedestrian/motorcycle they crashed into. The claim is made so frequently that certainly there must be a grain of truth to it. Yet it certainly isn't the case that car drivers can't see such obstacles -- after all, they can see traffic signals that are much smaller than a bike or a motorcycle.
What they mean to say is that their attention was otherwise engaged -- perhaps by a phone conversation, perhaps by…
dmunger | February 19, 2008Take a look at this amazing illusion created by Arthur Shapiro (you'll need the latest version of Flash Player to see it):
You're looking at two donut-shaped figures whose "holes" are gradually changing color from black to white and back again. It appears that the holes are changing in an opposite pattern -- when one is light, the other is dark, and so on. But if you click to remove the surrounding donuts, you'll see that the two holes are actually changing together.
If you're still not convinced, get a friend to help. One of you looks at the light donut and the other looks at the dark…
dmunger | September 18, 2007Take a look at this video (QuickTime required). The screen will turn white for 1/2 second. Then a word will appear for about 1.5 seconds. Pay attention to the particular shade of gray the word is printed in. Next, a strip of five different grey squares will appear. Which square matches the color of the word?
It's a difficult task, but not impossible (we'll collect answers in a poll at the end of the post). A team led by Brian P. Meier had college student volunteers complete a similar task, and they were able to achieve 30 percent accuracy -- somewhat better than the 20 percent you would…
dmunger | July 5, 2007A continuation of our "greatest hits" from past Cognitive Daily postings:
[originally posted on May 9, 2006]
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,…
cogdaily | July 2, 2007This is a guest post by Jonathan Leathers, one of Greta's top student writers for Spring 2007.
Take a look at this word:
MONDAY
What color do you see? Red? Blue?
While you may see nothing unusual, some people report being able to perceive colors associated with different days of the week when they are written down or heard in conversation. This ability is attributed to a phenomenon known as synesthesia, previously thought to be extremely rare. In synesthesia, the human brain interprets one set of sensory stimuli in terms of another; in other words, two senses cross. But synesthesia goes…
cogdaily | June 11, 2007This is a guest post by Suzie Eckl, one of Greta's top student writers for Spring 2007
Forget color television.
Before we had color, we had black and white. Before we had movies, we had photographs. And before photographs we had...
Engravings?
Prior to August 19, 1839, the date Daguerre and Niepce revealed that they had created the world's first photograph, artists had all the control in reproducing the world as they saw it. Many artists chose not painting or sculpture but engraving. They carved their images into wood or burned them into metal.
In a fascinating analysis, Danielle Zavagno…
dmunger | May 9, 2007"I just didn't see him" is a claim that's repeated over and over in accident reports. Drivers earnestly claim that they simply didn't notice the bicycle/pedestrian/motorcycle they crashed into. The claim is made so frequently that certainly there must be a grain of truth to it. Yet it certainly isn't the case that car drivers can't see such obstacles -- after all, they can see traffic signals that are much smaller than a bike or a motorcycle.
What they mean to say is that their attention was otherwise engaged -- perhaps by a phone conversation, perhaps by other traffic, or perhaps because…
dmunger | March 13, 2007Take a look at the image below. Your job is to find the T among the sea of Ls. If you're like most people it will take just a second or two.
Figure 1:
If you repeat this task several dozen times, each time with a new set of Ls and T in different colors, positions, and orientations, you'll get quicker at the task. Try this one -- again, look for the T.
Figure 2:
But what if a pattern was repeated later on? Would you remember it? Would you be quicker? Take a look at this figure; again, look for the T:
Figure 3:
Here, the pattern of colors is the same as in Figure 1, and the T is in the same…
dmunger | September 14, 2006Color categories, as we pointed out in this post, are remarkably consistent, even across different cultures and languages. "TLTB" pointed out in the comments that for people with color blindness, the color categories might not make much sense. He brought up an excellent point, one that becomes doubly perplexing when we realize that no two individual eyes are the same -- indeed, retinal scanning is considered more accurate than fingerprints in establishing someone's true identity.
The distribution of cones and rods across the retina varies substantially. What's more, the macula, a region in…
dmunger | September 11, 2006The World Color Survey is a massive project which attempts to understand how colors are categorized in different languages. The researchers studied 110 different languages, none of which had a written component, which ensured that only spoken word categories would be used to describe the colors.
Do the speakers all understand colors the same way? Is "red" red whether you're speaking Chumburu or Saramaccan? Rolf Kuehni undertook an analysis of the data to try to find out.
To discuss colors and language, it's important to differentiate between the word we're using to describe a color, and the…
dmunger | July 20, 2006[article originally posted September 27, 2005]
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. "…
dmunger | June 29, 2006One of the amazing things about the Stroop Effect is how much good research is being done based on this simple phenomenon, over 70 years later. One of the neatest recent experiments was created by Peter Wühr and Florian Waszak. I think I've created a simple animation that replicates their results. Click on the image below to bring up a short animated GIF. You'll see an image flash quickly, followed by a blank screen. As quickly as possible after the image flashes, say the color of the rectangle in front. Ignore any words printed on the rectangles; you just want to name the color of the…
dmunger | May 19, 2006The 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…
dmunger | May 9, 2006The 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…
dmunger | March 16, 2006A 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.…