Movement and exercise
May 13, 2008
Category: Development / Aging • Movement and exercise • Research
Jim was an early, confident walker. Greta likes to say that he didn't learn to walk, he went straight to running. By the time he was about 16 months old, he could already outrun his already-pregnant mother.
Nora, on the other hand, was a late, tentative walker. She took her first steps at around 12 months, and still wasn't very confident as a walker at 18 months. In this photo, at 17 months, she still clings to their toy kitchen set for balance.
But I've just finished reading a fascinating study suggesting that at 14 months, when both of them were walking -- Jim with confidence, and Nora struggling -- they actually took a similar approach to balance while walking.
A team led by Jessie Garciaguirre might be the first to investigate how infants who've only recently learned to walk adapt to carrying heavy loads. Adults generally carry no more than 35 percent of their own body weight (though in some African tribes, women balance immense loads -- up to 70 percent of their body weight -- on their heads). School-age kids might port 20-30 percent of body weight in backpacks on their way to school. Adults and kids make significant adjustments to posture and gait when bearing loads in excess of 15 percent of body weight. They take shorter steps, and they lean away from the load to compensate (generally this means leaning forward to accommodate a backpack).
So why not put backpacks on toddlers and see how they manage? Garciaguirre and Karen Adolph had previously found that 14-month-olds fall down an average of 15 times per hour while playing. What could possibly go wrong when heavy weights are strapped to their backs?
Read on »
Posted by Dave Munger at 3:09 PM • Comments (3)
April 15, 2008
Category: Movement and exercise • Reasoning • Research
Clicking on the link below will bring up an image in a new window (you may need to disable pop-up blockers to do this). The picture contains five rows of asterisks. Your job is to count them as quickly as possible. Try using your finger to point and help keep track.
View image
Now try the same task again, only this time, keep your hands flat on the table while you count.
View image
If you're like most people, this second task was a little more difficult for you. It's not that you need to use your finger to help you count, it just seems to help things along a bit. When you weren't using your finger to point, you may have found yourself nodding your head to help keep pace with all those asterisks.
A team led by Richard Carlson gave 24 tests like this to 17 students, and verified that pointing to help count asterisks resulted in faster and more accurate counts. But why? Maybe the fact that the items being counted are all asterisks tripped up the students, and they had to use their fingers just to keep their place. Carlson's team repeated the study, only using a variety of different symbols, not just asterisks. They found the same result. Even for a simple counting task, pointing at the things we count makes it easier. But once again the question arises: how is it that simply pointing at things helps us count?
Read on »
Posted by Dave Munger at 2:07 PM • Comments (11)
April 8, 2008
Category: Movement and exercise • Research • Social
In our little college town, one of the most popular fitness trends over the past few years has been yoga. Friends and acquaintances often suggest we join them in their favorite class, claiming not only that we'll get stronger and more flexible, but that we'll feel better about ourselves.
But Greta and I both have fitness routines that work well for us. I like to go for a morning run, I bike, and I play soccer, and Greta not only walks for 30 minutes on the treadmill every day, she also walks to and from work, 1.3 miles each way. Despite our assurances that we enjoy these things, devout yoga fans seem convinced that we're missing out on something: a chance to improve our self-esteem.
Despite all the hype about yoga and self esteem, there hasn't been a lot of research demonstrating a connection, especially in comparison to other forms of exercise. But Steriani Elavsky and Edward McAuley have conducted a new study comparing yoga to walking. They recruited 164 women age 42 to 56, with offers of a free fitness program. At the study outset, all the women were paid $20 to undergo both psychological testing for measures such as their body image, physical self-esteem, and global-self esteem, as well as physical measures like weight and body fat percentage. Then they were randomly divided into three groups: yoga, walking, and control (no exercise).
Read on »
Posted by Dave Munger at 2:34 PM • Comments (37)
March 31, 2008
Category: Movement and exercise • Perception • Research
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, instead of accurately walking the distance, they systematically overestimated the distance to the object. Could our feet deceive us more than our eyes, even when we're simply asked to retrace a path we've just taken?
There's another possible explanation: maybe being led is what causes the deception. In a new study, Ellard and Sarah Shaughnessy asked 30 volunteers to walk blindfolded along a roped-off 10-meter pathway. They could use the ropes to guide themselves, but were never led by researchers. As before, they walked the distance to the object, then returned to the starting point, and finally attempted to walk the same distance again. Another group of volunteers simply looked at the object and then tried to walk to it blindfolded. Here are the results.
Read on »
Posted by Dave Munger at 2:28 PM • Comments (13)
March 26, 2008
Category: Attention • Movement and exercise • Research • Video Games / Technology
[This article was originally published in January of 2007]
Many 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 results that talking with a passenger is unequivocally safer than talking on a phone, the research is impressive. The study comes from David Strayer's laboratory, the same group that has conducted a number of studies demonstrating the danger of driving while talking on the phone.
The researchers, led by Frank Drews, recruited 48 pairs of licensed drivers to participate in a driving / talking task. Drivers were selected randomly, and were paired with people they were friends with outside of the study. Each pair was told to talk about about a "close call" -- a time when their life was threatened -- either on a cell phone or in person, while one of the people drove an eight-mile course on a driving simulator.
The conversation topic was the critical portion of the task, because previous studies comparing conversations with passengers versus on cell phones have found driving ability to be equally impaired. In these tasks, typically the passenger and driver had to complete a difficult task such as thinking of a word that starts with the last letter of the word their partner said, often under competitive circumstances: arguably this is not analogous to a real conversation in a car. The "close calls" topic was chosen because other studies had revealed that it leads to naturalistic conversations.
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Posted by Dave Munger at 8:49 AM • Comments (21)
February 13, 2008
Category: Memory • Movement and exercise • Perception • Reasoning • Research
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 board, maybe expert hikers are better at remembering details about trails than novice hikers.
The classic study of expert and novice chess players was conducted in 1973 by William Chase and Herbert Simon, and found that chess experts could remember configuration of chess boards better than novices -- as long as the chess pieces were arranged in a plausible game configuration, and not just randomly arrayed.
Since then, dozens of studies have found that experts in a variety of fields have better memory for things related to their area of expertise, from football formations to chest X-rays. But according to a research team led by Satoru Kawamura, all of these results can be explained by perceptual chunking: Experts are better than novices at lumping information into manageable groups. Hiking scenes, they argue, aren't easily chunked in the same way. Do expert hikers still have better memory for scenes relevant to hiking?
Read on »
Posted by Dave Munger at 11:06 AM • Comments (17)
January 14, 2008
Category: Movement and exercise • Reasoning • Research • Social
I was a little surprised by an offhand observation Thomas Schubert made in a recent research report. He claimed that while men will commonly make a fist to celebrate a goal in a soccer match or a home run in baseball, it's unusual for women to do so.
I'm sure I've seen both female athletes and fans celebrating with fist pumps. But maybe I only noticed these cases because they were exceptions. Let's see if we can verify Schubert's observation with a little poll.
But there are additional gender dynamics to making fists besides who celebrates that way at a football game. At a minimum, a fist can signal an intent to hit someone (Schubert claims it's an abbreviation for the act of hitting itself). Researchers have found that males usually hit others with the intent to coerce or punish; women, by contrast, are likely expressing distress when they hit others. It's almost the opposite intention: speaking in generalities, men hit to establish their power, while women hit to express their powerlessness.
If hitting has a different meaning for men and women, then it falls to reason that making a fist also has a different meaning -- which might explain Schubert's anecdote about making fists in celebration. But studying body movement and how it affects thoughts and intentions is a tricky business (see, for example, this study on smiling). If you tell someone to make a fist and ask them how it makes them feel, is it the physical fist-making that causes the emotion, or the linguistic term "fist"?
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Posted by Dave Munger at 12:18 PM • Comments (16)
January 2, 2008
Category: Movement and exercise • Perception • Research
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 vertical distance isn't as big a problem: if she descends too slowly and carefully, she'll still live to tell the story.
On flat ground, overestimating distances could spell trouble: you might pack too much food for a hike, unnecessarily burdening yourself and perhaps not even making it to your destination. In fact, people do make systematic errors in estimating distance based on how much weight they're carrying; it's possible that they might make the same sort of errors estimating vertical distance. Since it takes more effort to climb up a mountain than climbing down, maybe we misjudge up distances as longer than down distances.
Russell Jackson and Lawrence Cormack took college students to the base of a 40-foot-tall wall and asked them to estimate the distance to the top by telling a research assistant to back away from the wall until their distance from the wall was equal to its height. Then they took them to the top of the wall and asked them to estimate the distance down using the same system (actually, half the students estimated the distance down first). This graph shows the results:
Read on »
Posted by Dave Munger at 9:05 AM • Comments (22)
December 6, 2007
Category: Attention • Face perception • Language • Movement and exercise • Research
When 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 that clip? Go ahead and replay the video to see if you can hear it the second time through.
That's right, I said two three-word phrases, not just one. If you're like me, you only heard background noise during the second part of the clip. In fact, I'm curious as to whether anyone can understand me at all. Let's make this one a poll:
Read on »
Posted by Dave Munger at 2:08 PM • Comments (27)
August 28, 2007
Category: Attention • Movement and exercise • Perception • Research
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 animals.
Fascinating as point-light displays are, however, we rarely see them in real life. Point-light displays
suggest that motion gives us a great deal of information about the object we're looking at, but we can't be sure that real-world perception works the same way. A team led by Quoc Vuong has conducted a study to see if what we know about point-light displays transfers to real-world objects and scenes.
They constructed a set of composite movies like this one (
QuickTime required):
In every clip, a machine was superimposed with either a walking human figure (like in this clip) or another machine. To make the task even more difficult, viewers were shown two movies simultaneously, for just two thirds of a second. Viewers had to determine if
one of the two movies included a human. The relative visibility of the human figure was also varied.
Even more critically, half of the images they saw were animated, and half were still photos. Here are the results:
Read on »
Posted by Dave Munger at 3:23 PM • Comments (7)
July 31, 2007
Category: Intentionality • Movement and exercise • Perception • Research • Social
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 it requires some external force, just like it's important to be able to tell the difference between a sleeping dog and a dog-shaped rock.
Perhaps this could be a job for mirror neurons: the mirror system, after all, is involved in both perceiving the motions of others and producing similar motions ourselves. But other areas of the brain are also involved in these types of actions. The social network, for example, is a set of widely distributed brain regions that are activated during social activities ranging from perceiving biological motion to judging the intentions of others.
Some studies have attempted to differentiate between these two systems by providing non-biological examples during fMRI imaging sessions. However, the research until now hasn't eliminated alternative explanations. A team led by Thalia Wheatley has devised a clever set of experiments using displays such as the one depicted above, in order to narrow down whether the mirror system or the social network is responsible for the decision about whether an object is animate or inanimate.
Read on »
Posted by Dave Munger at 11:44 AM • Comments (6)
June 18, 2007
Category: Movement and exercise • Perception • Research
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 broom, and his computer animated body contorts in a way that appears not humanly possible, we are reminded that it is just a computer generated figure. So what is it about physical movements that make them appear human or artificial?
Body language is a critical form of communication for human beings. We can pick up a lot of meaning from physical movements, even when we only see a very limited amount of information about that movement. For example, most special effects animation is created by putting sensors on several parts of the human body to determine how body parts interact when the body is in motion. A human figure made up of just ten dots located in the different major body regions is enough to convey a wide range of emotions and complex physical movements. How does this work? And what is it about this movement that allows us to distinguish natural movements from artificial ones? A research group lead by Jan Jastorff sought to answer these questions by testing if people could learn to distinguish between complex physical motions of artificial movements as well as they could distinguish between the complex physical motions of natural movements.
So what makes natural movements different from other types of movements? As Jastorff's team explains, biological movements have three distinct characteristics:
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Posted by Aaron Couch at 9:53 AM • Comments (6)
May 15, 2007
Category: Development / Aging • Movement and exercise • Music • Research
When Greta earned her Ph.D. 13 years ago, Jim was two and a half years old, and Nora was just 10 months old. Jim knew a few words, and Nora couldn't talk at all. You might think a baby as young as Nora wouldn't have an appreciation for music or dance. If you can't walk, what good is dancing?
But babies -- and Nora was no exception -- love to be bounced. Bouncing her on your knee would elicit peals of laughter. Is this love of rhythmic bouncing somehow related to an appreciation of music?
Jessica Phillips-Silver and Laurel Trainor developed an ingenious study to see if babies even younger than Nora in this picture could appreciate musical rhythm. Seven-month-old babies sat on experimenters' laps for two minutes while a simple rhythm was played:
Half the babies were bounced every other beat, and the rest of the babies were bounced on every third beat.
Then the babies were allowed to control the music themselves, based on where they looked. A light flashed, signaling the music was ready to start. The music started as soon as they looked at the light, and stopped when they looked away. Half the time the music was accented in the same pattern as the babies had been bounced earlier, so when the babies had been bounced every other beat it sounded something like this:
The other half the time it was accented every third beat:
So which music did the babies play longer? Here are the results:
The first two columns show the results of the initial experiment. Babies listened longer to the music that matched the bouncing pattern they had been exposed to previously. The experiment was repeated with the babies blindfolded during training, to make sure that it was the motion of the baby and not the visual stimulus of the "world" bouncing up and down that cause the effect. The results were the same. Finally, it was repeated once more when an experimenter bounced with the music as the baby watched. In this case babies expressed no preference.
Phillips-Silver and Trainor argue that this illustrates that there's a strong connection between body movement and rhythm even in babies as young as seven months old. So something like an appreciation for dance develops before babies can walk or talk!
Phill-Silver, J., & Trainor, L.J. (2005). Feeling the beat: Movement influences infant rhythm perception. Science, 308, 1430.
Posted by Dave Munger at 4:59 PM • Comments (3)
May 1, 2007
Category: Movement and exercise • Research
Kevin Granata, one of the authors of the work described here, was killed in in the shootings at Virginia Tech on April 16, 2007.
A back injury can destroy a person's life. The pain can be so excruciating that even "passive" activities like sitting up to read a book become intolerable. Whether you work in a steel mill or sit at a desk, a back injury can make it impossible for you to earn a living. Even worse, for many of those who suffer with chronic back injury, is that because it's difficult for others to see what's wrong, there's a tendency to not believe the problem is "real."
Yet there have also been significant efforts to prevent back injuries. For decades, it has been known that lifting heavy objects is an important cause of back injuries -- nearly everyone knows that you should "lift with your legs, not your back." Workplaces have been modified to reduce the amount of lifting workers must do, replacing lifting tasks with pushing or pulling when possible.
But pushing and pulling tasks can also cause back injury -- accounting for 20 percent of all workplace back injuries in the U.S., U.K., and Canada. Fifty percent of all industrial materials handling jobs involve pushing and pulling.
Granata and Bradford Bennet recognized that while much is known about the stresses placed on the back by lifting, little research has been done on the problem of pushing and pulling.
Read on »
Posted by Dave Munger at 3:24 PM • Comments (8)
April 26, 2007
Category: Face perception • Language • Movement and exercise • Research • Social • Video Games / Technology
There is a considerable body of research showing that eye contact is a key component of social interaction. Not only are people more aroused when they are looked at directly, but if you consistently look at the person you speak to, you will have much more social influence over that person than you would if you averted your gaze.
The problem arises when you address a group of people. How do you pick who to engage visually? Most public speakers are encouraged to look around the room, alternating eye contact with individuals in the audience. But there's no way to look at everyone at once -- so some of your potential social influence will by necessity be lost.
Now, a team led by Jeremy Bailenson has figured out a way to get around that limitation. In a virtual reality environment, there is no need for the representations of other people to be consistent. Since each individual's virtual experience is generated separately, in a "room" full of people, each person could experience the phenomenon of everyone else looking at them. Everyone can be the center of attention, all at the same time!
In the figure, person A believes that both B and C are looking at her. But in C's virtual world, both A and B could be shown as looking at her instead.
Bailenson's team wanted to see if they could use this method to allow one person to increase his or her influence over more than one other person simultaneously, by programming her "avatar" -- the virtual representation of herself -- to be looking directly at each of the others.
Read on »
Posted by Dave Munger at 2:45 PM • Comments (21)
March 27, 2007
Category: Development / Aging • Memory • Movement and exercise • Research
When we see a familiar face, or even a photo of a favorite car or pet, we're often flooded with memories from our past. Sometimes just seeing a person or object that's similar to the ones in our memory will trigger recollections we never knew we had. Maybe you've had a memory triggered by a scent or the texture of an object. Sometimes emotions such as happiness or anger will spur vivid memories, too.
A new study adds an unexpected method to the list of ways to spur memories about our past: body position. That's right: just holding your body in the right position means you'll have faster, more accurate access to certain memories. If you stand as if holding a golf club, you're quicker to remember an event that happened while you were golfing than if you position your body in a non-golfing pose.
Even more fascinating than the facts about body position and memory is how they were learned. A team led by Katinka Dijkstra actually had young adult and older adult volunteers assume different body positions while asking them to remember particular events from their lives. Sometimes the body position matched the memory:
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Posted by Dave Munger at 3:38 PM • Comments (15)
Cognitive Daily reports nearly every day on fascinating peer-reviewed developments in cognition from the most respected scientists in the field.
