Perception

This morning I went into the darkest room in our house (the kids' bathroom), closed the door, and turned off the lights for 5 minutes. There was enough light coming in through the crack in the door that after a minute or two I could begin to make out shapes in the room: A towel rack, the shower curtain. My eyes had adapted to the dark condition. Then I closed my right eye and covered it with my hand. I turned the lights back on, for a minute, until my left eye had adapted to the light. Then I turned the lights off. I could still see the towel rack and shower curtain with my right eye, which…
We're pretty good at remembering objects in a complex scene. We can even remember those objects when we move to a different location. However, the research so far has found that memory for the original view is a little better than memory when we've moved to a different location. Much of that research, however, has focused on relatively complex movements: Viewers are asked to remember an array of objects viewed from one side of a room, then are transported to a different part of the room and asked to decide whether the objects are arranged in the same pattern (actually, they're sitting at a…
The easiest way to talk to someone else is face-to-face. If you can see the movements of a person's lips and facial muscles, you can more easily work out what they're saying, a fact made obvious if you're trying to have a conversation in a noisy environment. These visual cues clue our brains in on how best to interpret the signals coming from our ears. But what happens when that's not possible, like when you're chatting on the phone or listening to a recorded message? New research suggests that if you've spoken to someone before, your brain uses memories of their face to help decode what…
Researchers have known for some time that people are surprisingly accurate at visually judging distances to objects as far as 25 meters away. If you're allowed to briefly look at an object up to that distance away, then blindfolded, you'll walk right up to it with great precision. If you walk halfway, you can throw a ball the remaining distance, again, quite accurately. But in 2000 Marla Bigel and Colin Ellard attempted a simple replication of the study: instead of viewing the object, volunteers were led blindfolded to the object and back, and asked to walk back to the object again. Now,…
Farris et al. have a paper coming out in Psychological Science about how men tend to misperceive sexual interest in women. I get the sense that this is a big problem for many women. Any woman who has spent more than 30 seconds in a bar has had at least one random yo-yo hit on them despite what they perceive as clear negative signals. So I am happy that someone is addressing this issue. I do have a couple concerns about this paper, but let's leave those til the end. Farris et al. sought to distinguish between two theories about how men misperceive sexual interest from women: Two main…
Bad experiences can be powerful learning aids for our sense of smell. A new study reveals that electric shocks can make people more sensitive to the differences between very similar chemicals that previously smelled identical. Every day, thousands of different molecules waft past our nose. Many of these are uncannily similar and some are more important to others. Wen Li from Northwestern University wanted to see how people learn to distinguish the critical smells from the unimportant ones. Smell the difference Working in the lab of smell guru, Jay Gottfried, Li attempted to train 12…
Do you recognize the faces in this picture? Sure you do -- you could recognize the authors of this blog anywhere, even upside-down. It might take you just a bit longer to realize that something isn't quite right with the picture. I'll show you what the problem is at the end of this post. We've known for decades that the human perceptual system is especially good at recognizing faces, but that ability breaks down in predictable ways when the faces are upside-down. While it takes us a bit longer to recognize objects when they are inverted, faces take even longer compared to other things. For…
Point-light displays are an amazing demonstration of how the visual system creates order out of what initially seems to be a random pattern. Take a look at this short movie (QuickTime required). Just looking at the first frame, it might be difficult to tell what's being displayed, but after watching for just a second, it all becomes quite clear: Just these 13 dots, when placed in motion, instantly convey a very clear picture. We can even determine the gender of the person walking or recognize friends, just from displays like this. But now take a look at this movie: It might take a bit…
Modern brain-scanning technology allows us to measure a person's brain activity on the fly and visualise the various parts of their brain as they switch on and off. But imagine being able to literally see what someone else is thinking - to be able to convert measurements of brain activity into actual images. It's a scene reminiscent of the 'operators' in The Matrix, but this technology may soon stray from the realm of science-fiction into that of science-fact. Kendrick Kay and colleagues from the University of California, Berkeley have created a decoder that can accurately work out the one…
Take 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 donut…
Which of these two pictures is more memorable? The shot on the left is interesting primarily because Nora's in it -- if it was just a picture of a muddy trail, it wouldn't be notable at all to most people. The shot on the right is a dramatic mountain scene that you might remember even though (or perhaps because) there's not a human in sight. But a seasoned hiker might be more interested in the photo of the muddy trail, which gives more information about the difficulty of the hike than a panoramic shot. Just as expert chess players are good at remembering the position of chess pieces on the…
Take a look at this short video clip (QuickTime required). It's called an RSVP (rapid serial visual presentation), meaning that it's a quick sequence of still images. In this case, it's a random sequence of letters. Your job is to look for a number among the letters. At some point during the clip, you should also see a dot flash in one corner of the video. You also need to take note of the corner in which the dot appears. A rectangle will flash shortly before the dot, possibly giving a clue to where the dot will appear: It's actually not a very difficult task (especially when I tell you that…
When we watch a movie, we're usually not conscious of the cuts made by the editor. The camera angle may change dozens of times during a scene, and we follow along as if the flashing from one viewpoint to another wasn't at all unusual. You might think this is just because we've been accustomed to watching TV and movies, but researchers have found that even people who've never seen a motion picture have no difficulty following along with the cuts and different camera angles in a video. But little research has actually been done on the impact of changing camera angles in a movie on our…
Take a look at this slideshow (QuickTime required). You'll first see a photo in perfect focus. Then 12 more pictures will flash by, each of them blurred using Photoshop. Finally, the original photo will appear again. Is it the same as before, or slightly blurrier or sharper? I'll give the answer after a few readers have had a chance to make a guess in the comments. Most people with normal vision will gradually adapt to blurry photos (though it might take a little longer than I've allowed in this movie). Then when they see a photo that's in focus, it seems too sharp -- as if it's been…
You might think humans are equally good at estimating distances no matter which direction they're looking. After all, we use the same visual tools to make those estimates -- binocular disparity (the different views we see from each eye), occlusion (whether one object is in front of or behind another), and so on. But consider the situation depicted to the right. Nora is inching her way down a steep rock column, with near-vertical drops on either side of her. If she underestimates the distance to flat ground below, she might decide she doesn't need to worry about falling. Overestimating the…
[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…
[Originally posted on February 20, 2006] Here's a picture of our daughter Nora at about 3 months of age. She looks like she's fairly aware of the events going on around her (arguably more aware than she sometimes appears now, at age 12). However, as our knowledge of how infants begin to perceive the world around them has increased, we've learned that the world of a three-month-old literally looks different to them than the world we perceive as adults. That's because vision, which seems so obvious and instinctive, is actually an active process. When we perceive the world visually, we're not…
Vision is the process by which the brain converts the light stimuli into a mental world filled with abstract visual objects. If you stop to think about it, this is an incredible feat. There is nothing in the photons coming from two neighboring sections of an object that implies that they should go together; rather the brain parses this information and forms it together into objects. Scientists thought they had a good model for how this happens, but Roelfsema et al. show in an excellent recording experiment in monkeys how that model is flawed. Background One of the important parts of vision…
This article was originally posted on May 10, 2006 Recent research suggests that one of the reasons that as many as 97 percent of women and 68 percent of men experience food cravings is because of visual representations of food. When we picture food in our minds, our desire for the food increases. So why not just distract the visual system? One research team attempted just that, tempting volunteers with pictures of chocolate, and then distracting them with either a randomly changing visual image or an auditory task. The participants who watched the visual image experienced fewer food cravings…
Does 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…