April 23, 2009
Taking pride in your posture:
A simple but elegant study just published in the European Journal of Social Psychology found that getting people to generate words about pride caused them to unknowingly raise their posture, while asking them to generate words about disappointment led to an involuntary slouch.
The research team, led by psychologist Suzanne Oosterwijk, asked people to list words related to 'pride' and 'disappointment', and some emotionally neutral control categories of 'kitchen' and 'bathroom', while being secretly filmed.
'Pride' caused a slight increase in posture height, while 'disappointment' caused the participants to markedly slouch.
The researchers suggest that the activation of the concept of disappointment led to a spontaneous bodily simulation of the feeling. They link this to the idea of embodied cognition that suggests that our mental life is fundamentally connected to acting on the world.
As we discussed last year, research has suggested that bodily expressions of pride and shame are the same across cultures, indicating that this connection between action and emotion may be a core part of our emotional make-up.
Link to abstract of study (via the BPSRD).
—Vaughan.
February 11, 2009
Bionic arm technology reroutes nervous system:
Damn this is cool. The New York Times has an article on an innovative technology that allows people to naturally use mechanical prosthetic arms.
While most of the media attention has been focused on implanting electrodes directly into the brain as a form of 'neuroprosthetics', this technology takes a novel and remarkably ingenious approach with impressive results.
The technique, called targeted muscle reinnervation, involves taking the nerves that remain after an arm is amputated and connecting them to another muscle in the body, often in the chest. Electrodes are placed over the chest muscles, acting as antennae. When the person wants to move the arm, the brain sends signals that first contract the chest muscles, which send an electrical signal to the prosthetic arm, instructing it to move. The process requires no more conscious effort than it would for a person who has a natural arm.
Researchers reported Tuesday in the online edition of The Journal of the American Medical Association that they had taken the technique further, making it possible to perform 10 hand, wrist and elbow movements, a big improvement over the typical prosthetic repertoire of bending the elbow, turning the wrist, and opening and closing the hand.
It's an inventive technique because it takes a whole chunk of the hard work away from the technology.
With neural implants, the major obstacle is developing the technology to reduce the noisy neural information into simpler signal channels. The patient then needs to be trained to generate the right brain activity to funnel the activity into the broad channels of the digital signal processor.
This technology takes advantage of existing healthy nerves but just reassigns them to other muscles and the activity in these is just converted into mechanical actions.
Of course, it isn't useful for people who are completely paralysed, but the results are quite spectacular.
The article has an embedded video which illustrates the remarkable dexterity that the woman with the prosthetic arm is able to achieve.
The scientific article describing the technology has just been published in the Journal of the American Medical Association and describes five prosthetic limb patients who were asked to complete a number of manual dexterity tests.
The study found that they completed tasks only marginally less well than comparison participants who had no damage and were using their original arms.
UPDATE: Mo has reminded me that Neurophilosophy covered an single case of the same procedure earlier in its development cycle. Mo also notes that the technology has the potential to feed-back touch information to the phantom limb!
Link to NYT article 'In New Procedure, Artificial Arm Listens to Brain'.
Link to scientific article.
Link to JAMA entry for same.
—Vaughan.
November 18, 2008
Mirror's Edge as proprioception hack:
Mirror's Edge is a first person computer game in which you play an urban free-runner, leaping, sliding, and generally acting fly across the roofs of a dystopian city (see the trailer here). It looks good. In fact, it looks amazing. But, reportedly, to actually play it is even better, sickeningly better.
Clive Thompson, writing for wired.com, suggests that the total interactivity of the environment (if you can see something, you can jump on it, or off it) along with the visual cues about what your character's arms and legs are doing (they appear in shot as you run and jump) makes the game a convincing proprioception hack. In other words, it remaps your body schema so that you feel more fully that you are the character in the game. When your character runs fast, you feel it is you running fast. When you character jumps across between two buildings and look down, you feel a moment of sickening vertigo.
Research into illusions of proprioception --- your sense of where you body is in space --- has shown that our body map is surprisingly flexible. It is possible to mislocate your hand, for example, coming to believe that it is directly in front of you when in fact out at the side, or behind you (see video here). Jaron Lanier has reported on an early virtual reality experience he had that made him feel like he had the body of a lobster, with 6 extra limbs. The important feature of all these illusions is that they rely on precisely timed visual feedback. Although visual input can reprogramme our body image, it only does so when there is a tight coupling between what we see and feel. The importance is not the level of detail in what we see, but in the fluidity of the interaction. If Mirror's Edge makes you feel like you are really are doing Parkour then it is because it has the correct kind of visual feedback (your limbs, in a fully interactive world) with the correct timing.
A final thought: if a computer game really is immersive for something as visceral as free-running, isn't that kind of surprising, given how complex free running is physically, and how simple the commands used to control a computer game are? Perhaps what this is because when we automatise an action such as a run, a jump or a roll part of the process of making it automatic is losing the experience of the component parts. So, when a computer game feels like real, it is because real feels like nothing -- we just ask our brains 'jump' and the motor system sorts out the details without our any deep experience of how the jump is performed.
link Clive Thompson's report on playing Mirror's Edge
link YouTube trailer for the game
—tom.
August 12, 2008
The common language of pride and shame:
Wired Science covers an elegant study that suggests that spontaneous expressions of pride and shame are innate behaviours that are not significantly influenced by culture.
The researchers came up with the ingenious idea of comparing how judo wrestlers from the 2004 Olympics and blind judo wrestlers from the 2004 Paralympics celebrated and commiserated their matches.
This allowed a cross cultural comparison, but it also allowed a comparison with blind athletes who have never seen another person in the same position to copy their behaviour.
The new research, however, distilled from high-resolution, high-speed photographic sequences of sighted and blind judo competitors at the 2004 Olympics and Paralympics, suggests that most nonverbal responses to wins and losses are almost universal.
No cultural differences were observed among competitors from different countries and, aside from the shaking of the fists after a loss, sighted and blind athletes displayed remarkably similar nonverbal behavior.
In other words, it made virtually no difference what culture each individual came from, or even whether the person had seen another wrestler at the end of a match or not - the expression of pride was indistinguishable, suggesting that this may be a common expression that we all share.
There was a slight effect of culture on the expression of shame - as the researchers note "it was less pronounced among individuals from highly individualistic, self-expression-valuing cultures, primarily in North America and West Eurasia".
However, as there was no difference within cultures between sighted and blind individuals, they further suggest that both pride and shame are likely to be innate, but that shame display may be intentionally inhibited by some sighted individuals in accordance with cultural norms.
Link to Wired Science on elegant study.
Link to full text of paper.
—Vaughan.
March 31, 2008
Rock climbing hacks! (now with added speculation):
I'm going to tell you about an experience that I often have rock-climbing and then I'm going to offer you some speculation as to the cognitive neuroscience behind it. If you rock-climb I'm sure you'll find my description familiar. If you're also into cognitive neuroscience perhaps you can tell me if you think my speculation in plausible.
Rock-climbing is a sort of three-dimensional kinaesthetic puzzle. You're on the side of rock-wall, and you have to go up (or down) by looking around you for somewhere to move your hands or feet. If you can't see anything then you're stuck and just have to count the seconds before you run out of strength and fall off. What often happens to me when climbing is that I look as hard as I can for a hold to move my hand up to and I see nothing. Nothing I can easily reach, nothing I can nearly reach and not even anything I might reach if I was just a bit taller or if I jumped. I feel utterly stuck and begin to contemplate the immanent defeat of falling off.
But then I remember to look for new footholds.
Sometimes I've already had a go at this and haven't seen anything promising, but in desperation I move one foot to a new hold, perhaps one that is only an inch or so further up the wall. And this is when something magical happens. Although I am now only able to reach an inch further, I can suddenly see a new hold for my hand, something I'm able to grip firmly and use to pull myself to freedom and triumph (or at least somewhere higher up to get stuck). Even though I looked with all my desperation at the wall above me, this hold remained completely invisible until I moved my foot an inch --- what a difference that inch made.
Psychologists have something they call affordances (Gibson, 1977, 1986), which are features of the environment which seem to 'present themselves' as available for certain actions. Chairs afford being sat on, hammers afford hitting things with. The term captures an observation that there is something very obviously action-orientated about perception. We don't just see the world, we see the world full of possibilities. And this means that the affordances in the environment aren't just there, they are there because we have some potential to act (Stoffregen, 2003). If you are frail and afraid of falling then a handrail will look very different from if you are a skateboarder, or a freerunner. Psychology typically divides the jobs the mind does up into parcels : 'perception', (then) 'decision making', (then) 'action'. But if you take the idea of affordances seriously it gives lie to this neat division. Affordances exist because action (the 'last' stage) affects perception (the 'first' stage). Can we experimentally test this intuition, is there really an effect of action on perception? One good example is Oudejans et al (1996) who asked baseball fielders to judge were a ball would land, either just watching it fall or while running to catch it. A model of the mind that didn't involve affordances might think that it would be easier to judge where a ball would land if you were standing still; after all, it's usually easier to do just one thing rather than two. This, however, would be wrong. The fielders were more accurate in their judgements --- perceptual predictions basically --- when running to catch the ball, in effect when they could use base their judgements on the affordances of the environment produced by their actions, rather than when passively observing the ball.
The connection with my rock-climbing experience is obvious: although I can see the wall ahead, I can only see the holds ahead which are actually within reach. Until I move my foot and bring a hold within range it is effectively invisible to my affordance-biased perception (there's probably some attentional-narrowing occurring due to anxiety about falling off too, (Pijpers et al, 2006); so perhaps if I had a ladder and a gin and tonic I might be better at spotting potential holds which were out of reach).
There's another element which I think is relevant to this story. Recently neuroscientists have discovered that the brain deals differently with perceptions occurring near body parts. They call the area around limbs 'peripersonal space' (for a review see Rizzolatti & Matelli, 2003). {footnote}. Surprisingly, this space is malleable, according to what we can affect --- when we hold tools the area of peripersonal space expands from our hands to encompass the tools too (Maravita et al, 2003). Lots of research has addressed how sensory inputs from different modalities are integrated to construct our brain's sense of peripersonal space. One delightful result showed that paying visual attention to an area of skin enhanced touch-perception there. The interaction between vision and touch was so strong that providing subjects with a magnifying glass improved their touch perception even more! (Kennett et al, 2001; discussed in Mind Hacks, hack #58). I couldn't find any direct evidence that unimodal perceptual accuracy is enhanced in peripersonal space compared to just outside it (if you know of any, please let me know), but how's this for a reasonable speculation --- the same mechanisms which create peripersonal space are those which underlie the perception of affordances in our environment. If peripersonal space is defined as an area of cross-modal integration, and is also malleable according to action-possibilities, it isn't unreasonable to assume that an action-orientated enhancement of perception will occur within this space.
What does this mean for the rock-climber? Well it explains my experience, whereby holds are 'invisible' until they are in reach. This suggests some advice to follow next time you are stuck halfway up a climb: You can't just look with your eyes, you need to 'look' with your whole body; only by putting yourself in different positions will the different possibilities for action become clear.
(references and footnote below the fold)
footnote:
My intuition is that this is the area around which we feel 'an aura' if someone reaches towards us; this is completely unsubstantiated speculation however
References:
Gibson, J.J. The theory of affordances. In R.E. Shaw and J. Bransford,
eds., Perceiving, Acting, and Knowing, Erlbaum Assoc., Hillsdale. N.J., 1977.
Gibson, J. J. (1986). The ecological approach to visual perception. Lawrence Erlbaum Associates Inc, US.
Kennett, S., Taylor-Clarke, M., & Haggard, P. (2001). Noninformative vision improves the spatial resolution of touch in humans, Current Biology, 11(15), 1188-1191.
Maravita, A., Spence, C., & Driver, J. (2003). Multisensory integration and the body schema: close to hand and within reach, Current Biology, 13(13), 531-539.
Oudejans, R. R., Michaels, C. F., Bakker, F. C., & Dolne, M. A. (1996). The relevance of action in perceiving affordances: perception of catchableness of fly balls., J Exp Psychol Hum Percept Perform, 22(4), 879-91.
Pijpers, J. R. R., Oudejans, R. R. D., Bakker, F. C., & Beek, P. J. (2006). The role of anxiety in perceiving and realizing affordances, Ecological Psychology, 18(3), 131.
Rizzolatti, G., & Matelli, M. (2003). Two different streams form the dorsal visual system: anatomy and functions, Experimental Brain Research, 153(2), 146-157.
Stoffregen, T. A. (2003). Affordances as properties of the animal-environment system, Ecological Psychology, 15(2), 115-134.
—tom.
July 18, 2007
Parapsychology, laughter and military neuroscience:
BBC Radio 4's All in the Mind just broadcast a wonderfully eclectic edition with pieces on parapsychology and why people hold paranormal beliefs, the psychology of laughter, and the military applications of neuroscience.
Dr Caroline Watt and Prof Chris French discuss both the current boom in scientific parapsychology research and the psychology of paranormal belief.
Prof Mark Van Vugt talks about the social function of laughter, something we featured the other day.
Finally, Prof Jonathan Moreno, author of the excellent Mind Wars, discusses the military applications of neuroscience, something he also tackled in a 2006 SciAmMind article.
Ghosts, gags and grunts. What a great combination!
Link to edition of BBC AITM with online audio.
—Vaughan.
May 10, 2007
The art of non-verbal attraction:
PsyBlog has just published a couple of short articles on non-verbal communication, one examining a common myth, and the other looking at how it indicates attraction between people who've just met.
The first article is on the research that debunks the myth that '93% of communication is nonverbal'.
Just the precision of those sorts of statements make me suspicious. To quote the wise words of comedian Vic Reeves "88.2% of statistics are made up on the spot".
The second article examines a study that looked at the dynamic patterns of non-verbal communication when men and women met for the first time, and looked at how these patterns were related to attraction.
Contrary to many previous findings, attraction was predicted by patterns of synchronisation and not simple mirroring of body language. What emerged were rhythmic structures of movement synchrony - patterns of bodily movement people adopted. In common with previous research, Grammer et al. (1998) found it was women who tended to start and control these patterns. Indeed, the more interested a woman was in a man, the more complicated these patterns became.
There's more on this impressive study in the PsyBlog article.
Link to article on myth of non-verbal communication.
Link to article 'The Nonverbal Symphony of Attraction'.
—Vaughan.
November 30, 2006
Shifting to light:
The first verse of the beautiful and evocative I Fellowed Sleep by Welsh poet Dylan Thomas:
I fellowed sleep who kissed me in the brain,
Let fall the tear of time; the sleeper’s eye,
Shifting to light, turned on me like a moon.
So, planing-heeled, I flew along my man
And dropped on dreaming and the upward sky.
Link to full-text of poem.
Link to Wikipedia page on Dylan Thomas.
—Vaughan.
March 27, 2006
New Psyche on 'action in perception':
A new edition of Psyche, the journal of the Association for the Scientific Study of Consciousness, has just been published online, and is a special issue on 'action in perception'.
The edition is curated by philosopher Alva Noë and takes a novel approach to understanding conscious perception.
The main idea of this book is that perceiving is a way of acting. Perception is not something that happens to us, or in us. It is something we do. Think of a blind person taptapping his or her way around a cluttered space, perceiving that space by touch, not all at once, but through time, by skillful probing and movement. This is, or at least ought to be, our paradigm of what perceiving is. The world makes itself available to the perceiver through physical movement and interaction.
This has some similarities with the later work of psychologist J. J. Gibson, who argued in his book The Ecological Approach to Visual Perception that perception could only be understood by accounting for the way in which in an organism uses vision to act within its environment.
Link to Psyche.
—Vaughan.
December 19, 2005
Sport psychology:
The Lancet medical journal has published a special sports supplement that for one month is available to view free as an e-magazine.
The 76 page publication includes features on aggression in sport (p.35); depression in sport (p.41), including comment on double Olympic gold medallist Dame Kelly Holmes' admission earlier this year that she deliberately cut her arms with scissors during a frustrating period in her career when she was unable to train because of injury; and risk taking in sport (p.38) - with discussion of the idea that extreme sports enthusiasts may use danger to kick-start their lower-than-average dopamine levels.
"The risk inherent in climbing such mountains carries its own reward, deep and abiding, because it provides as profound a sense of self-knowledge as anything else on earth. A mountain is perilous, true; but it is also redemptive". David Breashears, mountaineer and creator of IMAX film Everest, speaking about mountain climbing. From the article by Matt Pain and Matthew A Pain on risk taking.
Link to the supplement.
Link to high wire walker Philippe Petit talking to Sue Lawley on Desert Island Discs.
Link to editor Pia Pini talking about her favourite highlights from the supplement.
—christian.
October 04, 2005
Non-invasive neuroprosthetics:
Nature reports that by simply recording the brain's electrical signals from electrodes on the scalp, researchers have enabled trained participants to reliably control computer equipment, a feat normally associated with physical implants in the brain.
This is part of the growing science of neuroprosthetics, that aims to create technology that directly interfaces with the brain.
It is being particularly championed for people with paralysis, who do not have the use of their limbs, or people with damaged sensory organs, who might have their senses improved by technological replacements.
Previous trials of the technology have resulted in electronic implants to replace damaged retinas and a microchip implant that allows a paralysed man to control a computer.
These sorts of technologies typically require complex, experimental and invasive surgery, so being able to control technology via a skull cap and surface electrodes would be a more convenient option.
One of the disadvantages, well known to scientists who use forms of EEG recording to research the brain, is that the skull 'smears' the signal from the brain. Furthermore, muscle activity can introduce large amounts of electricial noise into the recording.
To get round this, mathematical analysis is used to filter out the unwanted interference, usually by averaging over several trials of the same task, allowing underlying brain activity to be inferred.
This is not an exact science, however, meaning the moment-to-moment 'decoding' of electrical activity needed for instant control of technology is more difficult to acheive.
Link to article 'Computer users move themselves with the mind'.
—Vaughan.
August 25, 2005
Getting to grips with grasping:
Reach and grasp a willing colleague by the arm, now let them go, and pick up a pen or pencil instead. The first movement requires a power grip, flexing all the fingers together towards the palm, the second movement uses a precision grip involving the thumb and forefinger. Easy to do? Apparently yes, but the ease and accuracy with which we reach and grasp objects (or people!) belies the complexity of the neural processing underlying such movements. Now the journal Nature Reviews Neuroscience has published a comprehensive review on the neuroscience of grasping, by Umberto Castiello.
Castiello describes how studies on the ‘kinematics’ of grasping have shown there is a reliable ‘landmark’ during reaching movements: when the hand is between 60 to 70 per cent of the way towards its target, the gap between the thumb and fingers always reaches its largest point, the precise moment correlating highly with the size of the object to be grasped. Other object characteristics – its weight, texture, surface – also affect aspects of the grasping movement in a lawful way.
Most of our knowledge about the brain networks involved in grasping come from intrusive experiments on monkeys that are simply not possible or ethical in humans. These point to a circuit involving the primary motor cortex, the premotor cortex and the anterior intraparietal sulcus. How similar things are in the human brain is a matter of controversy and ongoing investigation using brain imaging and studies with brain-damaged patients. These suggest many of the grasping-related areas implicated in the monkey brain are activated in the human brain too, but that other regions are also involved, including the prefrontal, somatosensory and cerebellar areas.
Castiello describes one patient, A.T., with extensive damage to the parietal lobe and secondary visual areas, who had problems grasping neutral, laboratory objects but was okay at grasping familiar items such as a lipstick. This suggests that, in humans at least, brain areas involved in interpreting the meaning of an object also influence the brain’s grasping circuit.
Indeed, Castiello says more research is needed into whether and how the meaning of an object, and intentions for what to do with an object, affect grasping in monkeys in the same way research has shown these more ‘cognitive’ variables influence grasping in humans.
“It will only be through careful and thoughtful experimentation, using converging techniques from the brain and behaviour, that we might completely understand the grasping function of the human hand”, Castiello’s review concludes.
Link to abstract of the review.
—christian.
May 29, 2005
Scott Adams and focal dystonia:
Scott Adams, the artist behind the comic Dilbert, has a movement disorder called focal dystonia that prevents him from drawing in the regular way. It, and his response to it, are discussed in an article in the Washington Post.
Focal dystonia, which can affect the hand (where it's commonly called "writer's cramp" when it affects writing), the neck (the most common site), eyelids or vocal chords, is something of a mystery. First reported in people who do fine finger work, including writers, seamstresses and musicians, it affects an estimated 29.5 individuals per 100,000 population [...] Often, focal hand dystonia patients are people who use the small muscles of the fingers and hands.
What I find most interesting about this condition is its neurological roots, as the fine finger work coupled with the stress that often triggers focal dystonia appears to "teach" part of the brain some broken connections:
"We think the disorder is largely associated with the basal ganglia," which are deep brain structures that help regulate movement, Karp [Barbara Karp, deputy clinical director of the National Institute of Neurological Disorders and Stroke (NINDS)] said. One theory is that repetitive movements or some other cause somehow trigger abnormal learning patterns in the brain.
One therapy for focal dystonia is "sensory training," changing techniques of practice so that the sensory areas of the brain can learn again how to give proper feedback to the motion parts. Adams, in his case, now uses a graphics tablet and draws Dilbert at many times the final size.
Link to Scott Adams, Drawing the Line in the Washington Post.
—Matt.
March 30, 2005
Tyrannosaurus reflex:
In a wonderful comic strip, dinosaurs explain the neural mechanism of why locking the hands together can release the knee jerk reflex.
It's not often the finer points of neurological examination are explained by cartoon dinosaurs, but may this be the first in a long line of comic book / neuroscience fusion spectaculars.
Link to dinosaur / neurophysiology comic strip (via tradetricks.org)
Link to information about the reflex examination.
—Vaughan.
January 20, 2005
Size and selection times: Fitts's Law:
Oo Oo - Just when I thought I was settling down to do some of the work i'm actually paid to do, I discovered a bit of psychology that is relevant to interaction design:-
Did you know that the time it takes you to point your mouse, or your finger, at something is predictable from the size and distance of the object using an equation known as Fitts's Law?
Nope, neither did I till today. But if you apply it right it shows how you can get a big gain in how quick and easy it is to select something with just a small change in the selection interface.
First, the maths. Quoting, Fitts's Law at a glance (lecture notes):
Fitts discovered that movement time was a logarithmic function of distance when target size was held constant, and that movement time was also a logarithmic function of target size when distance was held constant. Mathematically, Fitts' law is stated as follows:
MT = a + b log2(2A/W)
where
MT = time to complete the movement
a,b = parameters which vary with the situation ('regression coefficients')
A = distance of movement from start to target center
W = width of the target along the axis of movement (also equivalent to the degree of permissible error in movement target)
Fitts's Law is an example of a principle in psychology which was developed from information theory (you can read more about this here [1]). Although the basic message is obvious (big things are easier to select) it is the precise mathematical characterisation that is exciting, and that this characterisation includes a logorithmic function - which means that the shape of relationship between size and reaction time is curved so that small increases in size for small objects result make it much easier to select them (whereas small increases in size for big objects don't make that much difference). And the same applies for changes in target distance.
AskTog.com defines Fitts's Law as "The time to acquire a target is a function of the distance to and size of the target" and has some pleasingly opinionated notes on the application of Fitts's Law to interaction design:
While at first glance, this law might seem patently obvious, it is one of the most ignored principles in design. Fitts's law dictates the Macintosh pull-down menu acquisition should be approximately five times faster than Windows menu acquisition, and this is proven out. Fitt's law dictates that the windows task bar will constantly and unnecessarily get in people's way, and this is proven out. Fitt's law indicates that the most quickly accessed targets on any computer display are the four corners of the screen, because of their pinning action, and yet they seem to be avoided at all costs by designers.
Use large objects for important functions (Big buttons are faster).
Use the pinning actions of the sides, bottom, top, and corners of your display: A single-row toolbar with tool icons that "bleed" into the edges of the display will be many times faster than a double row of icons with a carefully-applied one-pixel non-clickable edge along the side of the display.
AskTog also has this quiz for interaction designers, all of the answers to which are based on some application of Fitts's Law.
Now for a typical GUI interaction lets suppose that the width of the thing you want to click on is about a ten times smaller than the distance you need to move to click on it. What is the effect of making the object closer, compared to making it bigger (and vice versa)?
Well for a range of distances (1 to 10) and a range of widths (0.1 to 1.0) the surface of the time-taken-to-move space looks like this:
If the 3D version is a little hard to understand, here's a flat version, with the same colour coding (red = longer time, blue = shorter time)
From this, I suggest that these things are true:
Decreasing the size/width of your target, if compensated for by an equivalent decrease in the distance of the target, won't have any effect on ease of selection. This is just moving along the leading diagonal space shown above.
but this is only true as long as the changes are equivalent percentages. The same absolute change to both target size and target distance could have a big effect on ease of selection
If selection is very slow, the most gains in ease of selection will first be made by making the target nearer (ie you start at the highest point of the movement time surface, the gradient is steepest along the 'distance' axis)
Then you will enter a region of the parameter space where equivalent (percentage) changes in distance and size will have comparable effects (ie the middle bit).
The final increases in ease of selection (ie decreases in movement time) will only be got by increasing target size.
Obviously, for any particular design problem you are working on the maths won't tell you which part of the parameter space you are operating in - but Fitts's Law does give you a model to start thinking about it
Refs
1. MacKenzie, I. S. (1989). A note on the information-theoretic basis for Fitts' law. Journal of Motor Behavior, 21, 323-330. (Online here)
2. Wikipedia article on Fitts's Law
—tom.
January 05, 2005
Waving, not designing:
I got a wave messaging power-up cover for my Nokia 3220 phone. It's got a line of LEDs along the back of the phone, and when you wave it, you can spell out messages in the air. Check this out:
(That's me, by the way. I posted more about this to my other weblog, if you're interested, but I'm going to continue here about embodied interaction and visual affordances.)
This phone is a pointer to something much larger: Embodied interaction is an up-and-coming trend in product and interaction design at the moment--why use just your fingers to select what's on a display when you can use your whole body? It's often easier, and makes more sense. Like, when you use a hammer, you don't key into system to say "hit at point X with force F" and then stand back and let it happen, you just pick up the hammer and hit with it, using your body to judge strength and your eyes to judge position.
Modern technology has always acknowledged the constraints of the mind and body, of course, but always implicitly. The keyboard works because the keys don't move around in function (the letter "B" is always the letter "B"), and because there aren't too many: that works well with our memory. The keyboard isn't too large, and that works well with the physics of how fast our hands can move, and what our handspan is. The icons on the screen feel like objects because we can move them round independently and they're outlined, and that's because of our built-in object recognition abilities. Windows on-screen can go behind one another because we realise that objects still exist when occluded by other objects, and buttons work well with shades of grey around them because we interpret shading and shadows and so the buttons look pressable.
Some bits of the computer interface take even more for granted. Imagine an alien using a laptop trackpad. They'd say "what? This is weird, you have to move a substance of a particular conductive property over this surface to make the cursor move round"--and that particular conductive property is that of our fingers, of course. (Try using your trackpad with a piece of plastic, it won't work. It's tuned to human flesh.)
Embodied interaction design does two things: It asks how we can have a more general interaction with our technology, so that instead of having to encode everything we do in terms of mouse movements and key presses, we can just do what we usually do. Also it asks: Just as we know the span of the hand to make a usable mouse or keyboard, what's the handspan of the brain so we can make an interface which takes advantage of that?
One great example of this in action is the iPod scrollwheel. You move round it with your thumb (it's a trackpad) to scroll, but actually it doesn't move--unlike the earliest iPods which did actually move. There's an interesting interaction design product there: With the early iPods, the moving scrollwheel was coloured white, the same as the rest of the mp3 player. You'd discovere the wheel moved just by picking up the device and touching it, the surface would yield. But with these new iPods, the scrollwheel doesn't move, so how should the designers advertise this capability?
The answer takes into account affordances (term coined by J J Gibson, used by the designer Don Norman, and in the book in "Objects Asked to be Used" [Hack #67]. When you see a coffee mug, you don't just see its colour, its shape, and the fact the handle is on the left, you see the possibilities of using it: immediately you see the mug, you left hand prepares to pick it up. By seeing the possibility of use, that action is represented in your brain, and because it's represented/encoded in your brain, you become more likely to perform that action. (This is just the same as when you scratch your nose. Somebody talking to you will have that action of "nose scratching" encoded in their brain. Just having that encoding active makes them more likely to perform that same action subsequently - scratching their own nose in turn - without realising it.)
Well, what does the scrollwheel need to do? It needs to visually advertise the fact that you put your fingers on it, grip, and pull round. We usually use rubber for grips, and we usually make it grey (people's fingers are carry a little dirt and with a lot of use the rubber gets grubby. Make the rubber grey to begin with, and the dirt doesn't show up). The fact that you don't actually grip the scrollwheel with your thumb is irrelevant. All the designers have to do is make you touch it once, and then the response of the interface will give you the feedback to confirm you made the right choice.
So that's what the designers have done: The scrollwheel is a dirty grey. It looks like it has been touched a lot. It looks rubbery (although it's not). It communicates the affordance of doing something when touched and dragged. And so, as a first-time user, that affordance gets encoded in your brain, and you have the bright idea of touching the iPod there, and: ta-da, you've done the right thing.
That's what easy-to-use interfaces are all about, and that - in a small way - is what embodied interaction is about too: understanding what the brain does (looks for visual affordances) and making use of that knowledge to transform a non-moving piece of plastic into something which begs to be used.
Now, how did I get to iPods and affordances from wave-in-the-air phones? Ah, doesn't matter, they're all part of the same design trend.
—Matt.
December 08, 2004
Sinister Research:
A couple of interesting bits of research on handedness in the news today.
Chimps brains are asymmetrical in similar ways to human brains, and this is reflected in whether they're left or right handed too. Why we have a preferred hand is still being debated, but this research shows handedness isn't a consequence of the same brain asymmetry which arose with language (the language centres are on the left side of the brain). Handedness must have arisen much earlier, and been present 5 million years ago.
In Mind Hacks, in "Test Your Handedness" [Hack #68], Karen Bunday points out one theory arguing that hand preferences come from our tree-dwelling past. One hand is mainly used for hanging on to branches, and the other hand used for finer, manipulative tasks like picking fruit. The difference in the hemispheres of the brain comes about when each optimises for slightly different behaviours. For example, spider monkeys tend to reach with their left hand. Use the keywords Postural Origins to search for more. (Personally, the idea that our brains were shaped by the literal shape of the forest canopy and the tree branching structure fascinates me. I'd love to know more about this, so recommended reads are much appreciated).
Which posturing brings us to the second piece of handedness research, related by BBC News Online: Left-handers 'better in fights', as found by looking at homicide rates in traditional societies and their left-handedness rate. Without reading the paper I couldn't be sure, but it can't be easy to get a causual relationship out of that, and the article does quote some sensible objections. But hey, it's a great headline.
—Matt.
