attention
dmunger | February 5, 2008A particular source of dread for politicians is how to respond to negative campaigning or other information impugning their character. By responding, they might only bring attention to an issue that voters hadn't even recognized: "Contrary to my opponent's claims, I have stopped beating my wife, and I haven't consumed more than a fifth of hard liquor in a single sitting."
Worse, many studies have found that even unequivocal denials fail to register in memory. In one study, participants read a report about the possible cause of a fire: a room full of oil paint and pressurized gas cylinders.…
dmunger | December 31, 2007[Originally posted on November 7, 2005]
What does it mean to have a gut feeling that you remember something? You see someone you recognize in a coffee shop. Do you remember her from high school? Or maybe you saw her on television. Could she be the manager of your local bank? Perhaps you don't know her at all ... but you've still got a feeling you do. What's that all about?
One theory of memory proposes that what we remember depends on our expectations. We're less likely to remember our old classmate at the coffee shop than at the high school reunion. At the bank, we might greet the manager by…
dmunger | December 13, 2007The human perceptual system is able to enforce a large array of illusions on our conscious experience. Most importantly, we hold the illusion of a complete and vivid picture of our surroundings, while in fact we selectively ignore nearly everything we see.
There's a good reason for this, of course: focusing on the task at hand generally consumes nearly all of the processing power our brains have to offer. If we need to shift our focus to another aspect of our surroundings, we can do it nearly instantaneously. But how do we decide which items to pay attention to? There are a couple…
dmunger | December 6, 2007When we are trying to understand what someone is saying, we rely a lot on the movement of their face. We pay attention to how their faces move, and that informs our understanding of what is said. The classic example of this is the McGurk effect, where the same sound accompanied by different facial movements gets interpreted differently.
Take a look at this short video clip (QuickTime required) of me talking, with my voice muffled by what sounds like cocktail party conversation:
Can you understand what I'm saying? What about after I stop moving? Can you understand me in the second part of…
dmunger | October 31, 2007Does this ever happen to you? You're preparing green beans to be cooked, putting the stems in the trash and the beans in a bowl. Suddenly you realize you've started putting the stems in the bowl. The dinner guests will be arriving soon, and now you have to search through the beans to pull out the stems, in order to avoid an embarrassing incident later that evening.
Okay, maybe it's just me. But what's the best way to find the stems? Is it faster to pore over the bowl, methodically scanning for each remnant? Or is it better to step back and take a holistic view of the bowl, letting the stems…
dmunger | September 4, 2007
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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…
dmunger | August 28, 2007
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…
dmunger | August 23, 2007
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…
cogdaily | July 12, 2007This is a guest post by Daniel Griffin, one of Greta's top student writers from Spring of 2007.
Does anything seem stick out about this sentence? I'm sure that if I told you to keep looking for yellow highlighted words, you would not have much trouble finding them in these first few sentences. You could even make it simpler for yourself and just look for any highlighted word. The only highlighted portions are yellow, so what is the difference? Let's say that by now you are used to searching for these highlighted words by just looking for a different color background than just the usual white…
dmunger | May 23, 2007The 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…
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 | May 3, 2007How 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…
dmunger | April 24, 2007The 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…
dmunger | March 15, 2007These 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…
dmunger | March 8, 2007Two 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…
dmunger | March 6, 2007What 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…
dmunger | February 27, 2007Our 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…
dmunger | February 22, 2007When 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…
dmunger | February 8, 2007Recently I attended a concert featuring the premier of an up-and-coming composer's work. She gave a brief talk before her piece was played, during which she explained the complex symbology of her work. The musical notes weren't just noises; they were intended to convey a meaning above and beyond a mere sequence of sounds. But if her music really did convey such deep meaning, why did she have to explain it to the audience beforehand? Can music ever express semantic meaning directly, without requiring a composer or someone else to "translate" for us?
Certainly not all music is as difficult to…
dmunger | January 24, 2007Many many studies have repeatedly shown the dangers of driving while using a cell phone. Yesterday, while discussing a new law in Britain imposing heavy penalties not only for driving using a handheld phone, but also while using phones with hands-free kits, commenter Jan claimed that talking to a passenger was less dangerous than talking on a phone. I replied that I hadn't seen a study demonstrating that talking with passengers was any different from talking on a phone, and Jan provided a link to one such study.
Greta and I have both read over the study, and while we can't say from these…