Working memory: "the bottleneck is not in the remembering, it is in the perceiving"
That quote is probably the most important sentence I have read in a year.
Working memory refers to the number of things a person can actively hold in memory at once, such as numbers or colors. Most people can remember about four things at once, and some can remember more.
MIT neuroscientists have found that the limitations on working memory do not come from limitations on remembering. Instead they come from how many things can be accurately perceived at once. We bump up against limits in visual perception in the process of encoding things into working memory even before we try to recall those things.
It gets better. The study also found that we do not have a working memory, but actually have working memories — two of them — one in each of the right and left hemispheres of the brain. The researchers concluded that the typical limit of four items in working memory at once was actually a limit of two items in the working memory of each of the two hemispheres.
“The fact that we have different capacities in each hemisphere implies that we should present information in a way that does not overtax one hemisphere while under-taxing the other,” said Timothy Buschman, the researcher who conducted the study.
I’ve been aware of the limits of working memory, and how this impacts the design of learning content in instructional technology, from research by Ruth Colvin Clark and Richard E. Mayer. The two ideas from Buschman’s study, though, raise some interesting additional questions.
What does it mean to balance the cognitive load between the left and right hemispheres? How should the visual design of instructional content reflect this idea? What could be done in content presentation that might increase the capacity or accuracy for visual perception in each hemisphere? How does pedagogy change if we recognize that perception is more important than recall in the capacity of working memory?
We already know that content delivered simultaneously through multiple modalities — such as visual and auditory — can increase the capacity of working memory. Does working memory related to other modalities also function as a dual system? Could this mean we actually have four (or more) distinct working memories that operate as an integrated system?
Education focuses so heavily on recall and pays so little attention to perception. This suggests that we really ought to consider whether we have things backwards.
The grand delusion: What you see is not what you get
Your senses are your windows on the world, and you probably think they do a fair job at capturing an accurate depiction of reality. Don’t kid yourself. Sensory perception - especially vision - is a figment of your imagination. “What you’re experiencing is largely the product of what’s inside your head,” says psychologist Ron Rensink at the University of British Columbia in Vancouver, Canada. “It’s informed by what comes in through your eyes, but it’s not directly reflecting it.”
Given the basic features of your visual system, it couldn’t be any other way. For example, every 5 seconds or so, you blink. Yet unless you’re thinking about it, as you probably are right now, you don’t notice the blackouts because your brain edits them out.
Blinking is just the tip of the iceberg. Even when your eyes are open they’re only taking in a fraction of the visual information that is available.
In the centre of your retina is a dense patch of photoreceptor cells about 1 millimetre across. This is the fovea, the visual system’s sweet spot where perception of detail and colour is at its best. “When you move away from the fovea, visual acuity falls away really quickly, and colour vision disappears,” says Rensink. About 10 degrees to the side of the fovea, visual acuity is only about 20 per cent of the maximum.
What that means is you can only capture a tiny percentage of the visual field in full colour and detail at any one time. Hold your hand at arm’s length and look at your thumbnail. That is roughly the area covered by the fovea. Most of the rest is captured in fuzzy monochrome.
And yet vision doesn’t actually feel like this: it feels like a movie. That, in part, is because your eyes are constantly flitting over the visual scene, fixing on one spot for a fraction of a second then moving on. These jerky eye movements are called saccades and they happen about 3 times a second and last up to 200 milliseconds. With each fixation your visual system grabs a bite of high-resolution detail which it somehow weaves together to create an illusion of completeness.
That’s remarkable given that during saccades themselves, you are effectively blind. Your eyes don’t stop transmitting information as they lurch from one fixation to the next, but for about 100 milliseconds your brain is not processing it.
Look in the mirror and deliberately flick your eyes from left to right and back again. You won’t see your eyes move - not because the movement is too fast (other people’s saccades are visible), but because your brain isn’t processing the information.
Given that you perform approximately 150,000 saccades every day, that means your visual system is “offline” for a total of about 4 hours during each waking day even without blinking (Trends in Cognitive Sciences, vol 12, p 466). Yet you don’t notice anything amiss.
Exactly how your brain weaves such fragmentary information into the smooth technicolour movie that we experience as reality remains a mystery. One leading idea is that it makes a prediction and then uses the foveal “spotlight” to verify it. “We create something internally and then we check, check, check,” says Rensink. “Essentially we experience the brain’s best guess about what is happening now.”
In conjuring up this “now”, the visual system has to do something even more remarkable: predict the future. Information striking the fovea cannot be relayed instantaneously to conscious perception: first it has to travel down the optic nerve and be processed by the brain. This takes several hundred milliseconds, by which time the world has moved on. And so the brain makes a prediction about what the world will look like about 200 milliseconds into the future, and that is what you see. Without this future projection you would be unable to catch a ball, dodge moving objects or walk around without crashing into things.
There’s another huge hole in the visual system that can render you oblivious to things that should be unmissable. The jerky movements that shift your fovea around the visual scene don’t happen at random - they are directed by your brain’s attentional system. Sometimes you consciously decide what to attend to, such as when you read. At other times your attention is grabbed by a movement in your peripheral vision or an unexpected noise.
The problem with attention is that it is a limited resource. For reasons that remain unknown, most people are unable to keep track of more than four or five moving objects at once. That can lead your visual system to be oblivious to things that are staring you in the face.
The most famous demonstration of this “inattention blindness” is the invisible gorilla, a video-based experiment created by Daniel Simons and Christopher Chabris at the University of Illinois at Urbana-Champaign. Viewers are asked to pay close attention to a specific aspect of a basketball game, and around half completely fail to see a person in a gorilla suit walk slowly across the screen, beat their chest and walk off again.
via NewScientist
Source: metaconscious
How we fool ourselves over and over
Christopher Chabris and Daniel Simons have now written a book, “The Invisible Gorilla and Other Ways Our Intuitions Deceive Us” about all kinds of illusions we suffer from. We think we see things as they really are, but “our vivid visual experience belies a striking mental blindness,” they write.
They cover the illusion of memory, how often our memories are born from our own embellished stories; the illusion of knowledge, we think we know much more than we actually do; the illusion of cause, we quickly assume correlation means causation.
The researchers are noted for their well-known experiment in selective attention, where participants are asked to count the number of times people in a video pass a basketball to one another. More than half of the participants are so attentive to the task, they fail to notice a woman wearing a gorilla suit cross through the middle of the basketball players, even though she stops and beats her chest before walking off camera.
Video: http://www.youtube.com/v/vJG698U2Mvo
Sensory perception, including vision, is subject to high levels of processing. Signals are picked up by our eyes or ears and transmitted through several levels of processing in the brain. Many signals are first interpreted by the limbic system searching for danger so that we can respond to that snake in front of us before we are even fully conscious of it. The various areas of the sensory cortex for vision, hearing, and touch gather the sensory patterns and organize them in a meaningful way by matching them to prior known patterns. Then the rear integrative cortex begins assembling all of the signals in order to try to understand what they are and what they mean. The signals are then passed to the frontal integrative cortex where executive processes occur, and then decisions are made about what actions to take in order to pass further signals to the motor cortex.
This is a simplification of one of many paths sensory data is understood and acted upon. In many other cases the signals bounce many times back and forth through different regions of the brain before reaching the level of cognitive awareness. These recursive functions offer suggestions that the brain acts as a complex system engaged in patterns of emergence. In fact, the brain is designed to filter out almost all incoming signals that are deemed unimportant so that the conscious mind can narrow attention to the things that are deemed most important and are most likely to require action or result in a reward.
This brief description does not even account for the filtering processes for what is or is not stored in long-term memory, a filtering process that has a significant impact on the accuracy of memory (with significant ramifications for such things as eyewitness testimony). This is enormously important for teaching and learning in education, and has even more fascinating implications about our awareness of the nature of reality (ontology) and the nature of knowledge (epistemology). Neither pre-Enlightenment mysticism nor post-Enlightenment rationalism have proven fully capable of explaining our inscrutable universe, but we have good reason to believe that our newest ideas of the embodied mind operating in a quantum universe are showing many positive signs of arriving at consilience among many disparate lines of inquiry.
