Perception

There are lots of people who, with training, can identify musical notes when they know the starting point -- when they hear a song starting with "C," they can name the rest of the notes in the song. But much rarer is the ability to identify musical notes without any context. This is what people are talking about when they talk about "perfect pitch" or "absolute pitch." Let's do a quick test to get a rough sense of how many CogDaily readers have absolute pitch. Listen to this note: Now, what note is it? Obviously these results won't be perfect, but they should give us a general idea. I'll…
Functional MRI (fMRI) is a very useful technique, but it lacks in resolution making some systems difficult to study. Adams et al. show in a study of ocular dominance columns in humans why good old staining is still useful when we reach the limits of imaging. Ocular Dominance Columns Ocular dominance columns are areas in the primary visual cortex (V1) of mammals that show a preference in activity to one eye over the other. (I think this applies to reptiles and amphibians as well, but I don't know that for sure). Here is a brief schematic of the visual system. The primary visual cortex is…
Yet another round of the unholy wars has broken out again here at Scienceblogs. Matt Nisbet and PZ Myers are at each others' throats. Again. If you read the other blogs here, you know that this isn't anything that's exactly novel. The two have some fundamental differences, and every so often those differences brush up against each other. When Matt and Paul's differences interact, we usually see something that chemists and science geeks like to refer to as a "highly exothermic" reaction. (In other words, things go "Boom!") I don't always get involved when these disputes come up, and when I…
width="70" height="85" /> Countless change blindness studies have showed that we're extremely bad at noticing when a scene has changed. We fail to notice objects moving, disappearing, or changing color, seemingly right before our eyes. But sometimes we do notice the change. What sorts of changes are we more likely to notice? I've created a simple demo that may (or may not) help answer that question. Take a look at this movie (QuickTime required). It will show a scene for six seconds. Then it will briefly flash white, and the same scene will be shown for another six seconds. Can you spot…
We can recognize the faces of our friends very quickly from just a snapshot. Within 150 milliseconds of being flashed a photo, brain signals respond differently to photos containing animals than photos with no animals. We can categorize scenes as "beach," "forest," or "city" when they are flashed for even shorter periods. But we also get a great deal of information from the motion of people and animals. We can identify our friends and family members just from a point-light display of them walking. We can also detect the emotions of point-light faces, and even the species of point-light…
Memory is a curious thing, and visual memory is even more curious. In some ways, we don't remember much about the scene that's right in front of us. As countless change blindness studies have shown, we often don't notice even obvious changes taking place in a scene. Other studies have concluded that visual short term memory has a capacity of just three or four objects. Yet I have vivid visual memories of scenes I have only glimpsed for a few seconds: A deer below the rim of the Grand Canyon; Michael Jordan draining a three-pointer to win the NBA championships; the standing ovation our…
When you look at a scene: a building, a park, a mountain, your visual system processes the information differently from when you look at a single object: a face, a pen, or a coffee mug. For example, this first image is from our trip to Prague this past summer: When you look at this picture, your eye might move first to the bridge, then to the lampposts on the bridge, to the castle in the background, to the overhanging limbs. The next picture is much simpler: It's a coffee mug, plain and simple. There's not much left to do with it. There are three regions of the brain that respond more…
Take a look at the following two circles. At the center, they're both the identical bright white. But which one seems brighter? Let's make this a poll: I'm not sure if this illusion will work when respondents know the objects are the same brightness, but naive viewers will reliably rate the circle on the left as brighter -- this is called the "glare effect," and it occurs whenever there's a gradual gradient around a circle or other shapes (the gradient must approach the color of the shape as it gets closer to the shape itself). I found the illusion so powerful that I had to close the…
On our recent trip to Europe, we had a hard time getting the kids to smile for pictures. Most of our pictures of Nora ended up looking something like this (actually this one's a self portrait, but you get the idea): Here her expression is basically neutral, and if it wasn't such a dramatic shot, it would be a bit boring. When we could get her to smile, often the smile was inauthentic -- posed, or even sarcastic, like in this shot: Here she's expressing mock excitement over her parents' excitement about the figure depicted in the statue: Leonardo Fibonacci, the great mathematician (click on…
When you have a conversation with someone, you're doing a lot more than just interpreting the meaning of the words they say. You're also trying to figure out what they intend to say and integrating that in to your understanding. You're working together with them to decide whose turn it is to speak. Your accents become similar. Your body movements become synchronized. You even scratch your nose at the same time as your conversational partner. It makes sense, then, if you're both looking looking at the same picture while you talk, that you'll look at the same parts of the picture at the same…
Take a look at this movie (QuickTime Required): The moving object is exactly the same in each picture, but the background is different. If you're like most people, you'll see one object as an ice skater, and the other as a spinning top. This puts the objects in two different classes -- animate (something that can move by itself: a human, animal, robot, and so on) and inanimate (something that requires an external force to move). Do we perceive the two objects differently? Arguably, it's important that we do: if an object can move by itself, it's much more likely to be a threat to us than if…
This is a guest post by Laura Younger, one of Greta's top student writers for Spring 2007. Take a look at these static images from a video clip. Can you tell what the person is doing? It might be hard to make it out from these still pictures, but when you see the same thing in motion it becomes quite clear. Visit the Biomotion Lab and you'll quickly understand. What you see is called a point-light display. Lights are attached to joints on the body and filmed while a person is performing an action. The animated display makes it surprisingly clear that this person is walking. But, could a…
A continuation of our "greatest hits" from past Cognitive Daily postings: [originally posted on 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…
A continuation of our "greatest hits" from past Cognitive Daily postings: [originally posted on July 11, 2005] There's something about kids and dogs. The phrase "A boy and his dog" brings up quite a range of images: from the sweetness of Norman Rockwell to what sounds like a truly bizarre movie from 1975. Despite not being a dog-person myself (okay, not being a pet-person at all), I find the results from a study that looked at kids and dogs amazing. Marina Pavlova and her colleagues at the University of Tüebingen were curious about how well kids would understand point-light displays.…
A 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,…
This 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…
This is a guest post by Laura Younger, one of Greta's top student writers from Spring 2007 Everyone has heard of the concept of reinforcement. You reinforce your child with dessert after finishing his or her vegetables; you praise your dog with ear scratches for not barking at the mailman; or you give yourself a little TV time for cleaning the bathroom. It's a system that often works, but what types of behaviors can be reinforced? We know that learning can be improved with reinforcement, but is external reinforcement required for learning to occur? A team of researchers led by Aaron Seitz…
This is a guest post by David Kerns, one of Greta's top student writers for Spring 2007. As movie special effects technology improves, more and more live-action shots are being replaced with computer animation. Harry Potter flies across the Quidditch field; Spider-Man swings from web to web through the cityscape of New York City, and miniaturized Hobbits fight the overpowering Orcs of Middle-earth. All of these are examples of human movements that have been reconstructed with computer animation. But sometimes this type of animation fails to come across as real. When Harry falls from his…
This is a guest post by Martina Mustroph, one of Greta's top student writers for Spring 2007. When you're typing, your senses of touch, hearing, and sight align. You feel, see, and hear your fingers touch the keyboard. Now imagine that you are outdoors and you feel a drop of water hit your hand. If you are like me, then it probably immediately occurs to you that it was a raindrop, so you stretch out your hand to see if more will come, and you look up at the sky for menacing clouds. Let's say the sky is blue and clear as far as you can see. Now your senses of touch and sight are at odds: your…
This 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…