Perception

This is a guest post by Daniel Griffin, one of Greta's top student writers for Spring 2007 How well do you think you can navigate through these woods? How about when your field of view is significantly reduced? When external information such as sight is decreased, our ability to make our way to a goal while avoiding obstacles will understandably be impaired.But when we lose all visual information we can still make mental representations, or "mental maps" of our surroundings. Even blind individuals compare with those who can see in tasks such as recreating large scale representations of…
This is a guest post by Aaron Couch, one of Greta's top student writers for Spring 2007 When looking out a window, or watching a movie in a theater, the image you see is typically presented as right-side-up. Let's say though, that you're lying on your side in bed and looking out a window at your backyard. Both your internal gravity sense organs and the orientation of scenery (trees, buildings) tell you that you're actually seeing a "tilted" image, and your mind immediately tells you which part of the scene is "up". In a similar vein, a team led by Ian P. Howard performed research that…
The visual system is very good at noticing a new object coming into view. However, the system isn't perfect. If a second object appears near the first one, it takes a little longer to spot it. This phenomenon, known as inhibition of return, has been well-documented. We discussed it in a 2005 post: If an object appears in one part of our field of view, it temporarily delays our ability to detect another object appearing near it. The effect begins about a third of a second after the first object appears and lasts about a second. If the second object appears sooner than that, we actually notice…
How many moving objects can you keep track of at once? Clicking on the image below will take you to Lana M. Trick's web site, where she has a nifty demo of a multi-object tracking task. You're asked to keep track one to four of the smiley-faces as they move randomly around the screen. Then when the faces stop moving, you click on the ones you were supposed to follow. Go ahead, give it a try! You'll notice there are four levels of difficulty. Most adults can, with a little practice, track four out of ten randomly moving objects for ten seconds -- they fall apart when there are more than…
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 searching arrays of letters like this, viewers were…
One "trick" dieters often use is to put their food on a smaller plate. The idea is to fool yourself into thinking you're eating more food than you really are. But doesn't our stomach tell us how full we are? Actually, it doesn't. Brian Wansink has devoted his career to studying how perception of food intake relates to actual eating behavior. Together with James Painter and Jill North, he's come up with a dramatic demonstration of how wrong our stomachs can be. Volunteers were recruited to participate in a soup-only lunch in a room adjoining the school cafeteria. They filled out a form asking…
If you're like me, when you read a book, you form a picture of what's happening in your mind. I try to imagine not only what the characters look like, but also their surroundings. Eventually, I've created a picture of an entire world in my head. Then, when the book gets made into a film, I'm often disappointed when things don't look the way I imagined them. Could it be that the visual environment I've created in my head is just as appealing as the one created by the filmmaker? It makes some sense: if we've gone to the trouble of creating a visual environment, why not use the part of our mind…
These two pictures represent the eye motions of two viewers as they scan a work of art with the goal of remembering it later. One of them is a trained artist, and the other is a trained psychologist. Can you tell which is which? How about for this picture? Art teachers have noted that when beginning students attempt to draw accurate portraits, they tend to exaggerate the size of key features: eyes and mouths are too big relative to the size of the head. Trained artists learn to ignore these temptations and draw the world as it really appears. Even world-famous artists such as Leonardo da…
Take 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…
Two days ago, we discussed research suggesting that the emotional qualities of images affect short-term memory for those images. When you watch a movie depicting a rapid sequence of images, you're more likely to remember images that have strong emotional content -- especially images that are arousing, whether they depict positive or negative things. Most fascinating of all: when we see images for a very short time, we're more likely to remember positive images, but when we view them for a longer period, we're more likely to remember negative ones. But our discussion didn't address some of the…
What types of images are you more likely to remember over the short-term? Pleasant? Bright? Arousing? Disturbing? One method of testing short-term visual memory is to flash a rapid series of pictures, then ask viewers which ones they saw. The pictures are shown so quickly that it's impossible to remember them all. Click on the image below to view a movie (Quicktime required). Wait for the entire movie to load, then watch it. You'll see 12 photos rapidly flash by. Play it twice, but no more. Other than the first and the last one, did you remember any? I'll put a quick test below (fair warning…
Our visual system is exceptionally good at detecting change -- as long as the change takes place while we're looking. If you glance at a scene, then look away for a moment, your ability to detect a change is substantially impaired. Changes that would be obvious when we're looking can become maddeningly difficult to detect if we're distracted for even a tenth of a second. Take a look at this quick movie (QuickTime required) -- the picture will alternate flashing with a distractor pattern. Each time the picture flashes, a portion of the picture will change in some way. Can you see what's…
When you look out the window and then look away, how do you remember what you saw? Do you hold a picture of the window in your head, frame and all? What about a photo? Do you remember the physical photo, or do you imagine the real scene it represents? If you remember the scene, and not the photo, then how do you form the boundaries of the scene? Does your memory end precisely where the photo does? Here's a little test to see how accurate your short-term memory of a photo is. When you play the movie below, you'll have a second to get ready, then a photo will flash for just a half-second. It…
Take a look at this animation. One face will flash; then it will be followed by another face. Are the two faces the same or different? The change between faces could be a small one. Did you notice a change? (You can repeat the movie once if you're not sure.) Let's make this one a poll: Now try another animation: Again, were the faces the same or different? Most people are much better at identifying different human faces than identifying animal faces, which makes sense, since most people have more experience with other people than with animals. Most adults are also better at distinguishing…
This is the best advertisement for a video game ever. The researchers compared people who played Unreal Tournament for 30 hours with people who played Tetris. They found that the Unreal Tournament players had an increase in visual processing speed: Video games that contain high levels of action, such as Unreal Tournament, can actually improve your vision. Researchers at the University of Rochester have shown that people who played action video games for a few hours a day over the course of a month improved by about 20 percent in their ability to identify letters presented in clutter -- a…
Nearly all video games that offer a first-person perspective -- where the view on-screen simulates what a real person would see as she navigates through the virtual environment -- also include a virtual map to help in navigation. Even my favorite golf game has one. Such maps can be indispensable, but they also invite a question -- should the map rotate to align with the player's viewing angle, or should they remain at a constant orientation? Aligning the map with the viewer's perspective makes it easier to find items, but constantly rotating the map might make it difficult for gamers to…
The binding problem is one of the great mysteries of modern neuroscience. Briefly, we know from a variety of studies in humans and primates that the specific features of the sensory world -- particularly the visual world -- are broken down into their separate components by the brain to be processed in parallel. This means that information for say color and information for say orientation are processed separately by the brain. The benefit of this system is that it allows your brain to take the insane amount of information in the perceptual world and process more of it, more rapidly. The…
In movie fight scenes, punches often miss by a foot or more, but when sound effects are added, and the punchee adds an effective-looking recoil, we're convinced that the punch is "real." We've posted on this phenomenon before: when a "click" sound is played as two animated balls pass by each other, it's perceived as a "bounce." This type of sound effect, where the sound occurs at a critical moment in an animation or movie, has been explored quite extensively. But is it possible that other types of sound might affect how we see motion? Adam Ecker and Laurie Heller realized that they could…
Keith Payne's work on racial stereotyping brings up an intriguing possibility. During the weapons identification task, viewers are more likely to erroneously identify a harmless object as a weapon if it was preceded by a black face compared to a white face. They are also more accurate identifying weapons after seeing black faces compared with white faces. It's possible that both of these results are due to the same underlying mental process, but Payne's research also invites another possible assessment: that separate processes are responsible for the two different behaviors. One behavior:…
The cafe wall illusion has the dramatic effect of making a straight line appear slanted: That's right, the line is precisely horizontal. It was created by Akiyoshi Kitaoka, one of the world's foremost authorities on visual illusion, who is also a wonderful artist. In addition to the hundreds of other illusions he's created, he's posted an entire page of illusions all based on the cafe wall effect. But why does the line appear to be slanted? It must have something to do with the juxtaposition of light and dark patches, but what exactly? Take a look at this more elaborate illusion which…