Do you remember what you ate a week ago?
Image: iStock/Barbara Dudzińska
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What did you eat for dinner one week ago today? Chances are, you can’t quite recall. But for at least a short while after your meal, you knew exactly what you ate, and could easily remember what was on your plate in great detail. What happened to your memory between then and now? Did it slowly fade away? Or did it vanish, all at once?
Memories of visual images (e.g., dinner plates) are stored in what is called visual memory. Our minds use visual memory to perform even the simplest of computations; from remembering the face of someone we’ve just met, to remembering what time it was last we checked. Without visual memory, we wouldn’t be able to store—and later retrieve—anything we see. Just as a computer’s memory capacity constrains its abilities, visual memory capacity has been correlated with a number of higher cognitive abilities, including academic success, fluid intelligence (the ability to solve novel problems), and general comprehension.
For many reasons, then, it would be very useful to understand how visual memory facilitates these mental operations, as well as constrains our ability to perform them. Yet although these big questions have long been debated, we are only now beginning to answer them.
Memories like what you had for dinner are stored in visual short-term memory—particularly, in a kind of short-term memory often called “visual working memory.” Visual working memory is where visual images are temporarily stored while your mind works away at other tasks—like a whiteboard on which things are briefly written and then wiped away. We rely on visual working memory when remembering things over brief intervals, such as when copying lecture notes to a notebook.
The question is: when are these memories wiped away? And when they are, can we still discern traces of what was originally ‘written,’ or does nothing at all remain? If visual short-term memories are only gradually wiped away, then remnants of these memories should still be retrievable; but if these memories are wiped out all at once, then we shouldn’t be able to retrieve them in any form whatsoever.
UC Davis psychologists Weiwei Zhang and Steven Luck have shed some light on this problem. In their experiment, participants briefly saw three colored squares flashed on a computer screen, and were asked to remember the colors of each square. Then, after 1, 4 or 10 seconds the squares re-appeared, except this time their colors were missing, so that all that was visible were black squares outlined in white. The participants had a simple task: to recall the color of one particular square, not knowing in advance which square they would be asked to recall.
The psychologists assumed that measuring how visual working memory behaves over increasing demands (i.e., the increasing durations of 1,4 or 10 seconds) would reveal something about how the system works.
If short-term visual memories fade away—if they are gradually wiped away from the whiteboard—then after longer intervals participants’ accuracy in remembering the colors should still be high, deviating only slightly from the square’s original color. But if these memories are wiped out all at once—if the whiteboard is left untouched until, all at once, scrubbed clean—then participants should make very precise responses (corresponding to instances when the memories are still untouched) and then, after the interval grows too long, very random guesses.
Which is exactly what happened: Zhang & Luck found that participants were either very precise, or they completely guessed; that is, they either remembered the square’s color with great accuracy, or forgot it completely. It was almost as if their memories behaved like files on a computer: Your Microsoft Word documents don’t lose letters over time, and your digital photos don’t yellow; rather, they continue to exist until you move them into the trash—where they are wiped out all at once.
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23 Comments
Add CommentWill you guys PLEASE stop comparing the brain to a computer. It is a false and misleading comparison, with no validity, if I remember correctly.
Reply | Report Abuse | Link to thisp.s.
Reply | Report Abuse | Link to thisAnd stop doing experiments based on that false assumption; "well a computer would do This!"
Of course human brain is not a computer, while the opposite is quite true: the most complex computer tries (rather unsuccessfully so far) to imitate human brain. Besides, the verb "compute" means "to determine especially by mathematic means", "to make calculation". Our brains do compute, even if computing is one of the lesser brain activities.
Reply | Report Abuse | Link to thisComparing the brain to a computer is somehow acceptable. It is a simile, for language's sake!
Reply | Report Abuse | Link to thisWell... some tries to make sense through visioning our thought as a mechanism with ubiquitous purpose. But the mind is free, and the purpose may come and go. There is no law that determines a sequential path from individual to individual. Sometimes it may be true, because aspirations are contagious. And memory should be permanent or not, long or short, as we feed our aspirations towards something, simple as that! Why should we be compared to a compurer that has the task to keep any memory?
Reply | Report Abuse | Link to thisA compurer simply is not a free being. It is a machine... an instrument that help us keep unworth things.
Sometimes we may think that we still need those unimportant things.But most of the time we don't, and we get lost, not knowing what to do with so many garbage. And we buy another computer with greater memory. It's alright, it's better have it in digital memory for our comodity and keep our mind to knew things. As we get older, we need it!
Brain IS a computer. But it is not as simple and uniform as the computers we build. When you research a complicated machinery it is quite valid to compare to simpler machines that you know how it works.
Reply | Report Abuse | Link to thisJust because you don't understand how a machine works does not mean it is not a machine... (And a reminder: a machine does not have to be fully deterministic)
" ..Our minds use visual memory..."
Reply | Report Abuse | Link to thisOh hell I'm sunk .... I only have one mind.
Brain is associative memory. Storing and Retrieval happen in associate way. Things/visuals which are associated with the existing memory/knowledge could be retrieved easily; which are not, will be somewhere in memory which could not be retrieved/reached like dangling thing. Over the period for efficiency reason it will fade away. For memory association is the key.
Reply | Report Abuse | Link to thisI have always considered myself to have had a photographic memory when I recall a memory I can literally see the image in my mind. As a kid at school I never did homework yet I was top of my class, I had excellent recall of everything that was taught to us, and everything I read. During exams, if I was unsure of something I had read I would picture the page in mind and re-read it, or I would recall a lesson and remember what the teacher had said.
Reply | Report Abuse | Link to thisI can still recall conversations months later verbatim, if that is not having a photographic memory, what is? In my younger years I travelled a lot, but never took photos but even today I can still recall the places I visited with vivid detail when describing them to others, even recalling specific shops and the order they were in.
Whereas if you asked what I had for dinner last night, I would not be able to tell you, in fact I would never have been able to tell you, why because it is not important enough for me to remember. But if you want to know what I had for dinner at a specific restaurant I have been to at some point I would be able to tell you exactly, why because I hardly ever go to restaurants. I can however tell you what my grandson did today, what he said to me and what he played with, and I could tell you the same for yesterday and last week. Unfortunately I am bloody shocking at remembering names, but I will never forget a face.
I just thought of something brilliant to say, but I forgot what it was.
Reply | Report Abuse | Link to thisTwo independent experiments, one for adults (can read and speak at the same time) and the other for toddlers (can only speak), should be performed. I doubt the so-called visible memory is highly related to other functionality of the brain, particularly, verbal and/or non-verbal communicability.
Reply | Report Abuse | Link to this"This prior knowledge changes how these images are processed, allowing thousands of them to be transferred from the whiteboard of short-term memory into the bank vault of long-term memory"
Reply | Report Abuse | Link to thisAnd these vague, made-up descriptions of what MIGHT be happening, without any empirical evidence to back them up, are the reason I gave up expecting anything substantive from the subject of psychology...
Simple question, What about blind People?
Reply | Report Abuse | Link to thisI recall discussions almost verbatim from my 5th year I am 76 now.
As for what I ate a week ago, not the foggiest idea,its not important. Perhaps I need the storage space to survive in this world?
Then answer this one. We are we inundated with TV and other visual adverts--repeatedly and constantly--why?
Is it not the Monkey see monkey do aspect?
Hi. What this long term memory is for? I think all that was developed to permit adaptation to changing environment, also in our movement, migration, as other animals. Conscious relevance is less important. We need visual LMT to recognize old as safe or dangerous, good feeling or bad feeling, and to enter new sceneries having similarities to good or bad old images and being enough cautious. All happens automatically, visual short and long term is not semantic nor symbolic, not strictly related to consciousness. You can remember all faces and quickly forget names, but not vice versa. And you create unconsciously a "proto-face" or a "proto-city", or a "proto-hotel" first of meeting or visiting or entering it for the first time. That is the istinct, or nose, that evolution gave to all migrant species.
Reply | Report Abuse | Link to this@promytius, i dont know if u r familiar with the term CONNECTIONIS in cognitive science, but if u r not, google it. that is basicly the future of cognitive science and it uses the computers to see if there is congitive relevance between hypothesis and theory and real life(actually, how our brain works). and it is NOT just comparing human brain to computers, it is much more... google it.
Reply | Report Abuse | Link to thisThese results are alright if one looks at then not from a memory point of view but from an orientation/attention perspective. Also the way the brain works is very important because if one tends to, unknowingly, spend most of his/her time thinking about something else the orientation/attention power is very low which means the time one is given to the stimulus is very low. Who has ever forgotten an accident of any sort? This is because the orientation/attention power is at its maximum during these situations and so the event is almost instantly memorized. I think that most of these studies are a bit waste of time as one should first identify the type of brain activity one has before doing any memory studies, but, hey, they may be fun to do them!
Reply | Report Abuse | Link to thisThe experiment does not account for completely trivial events that record like a photo a brief moment and is retained for decades for no discernible reason. I remember, while walking a neighborhood back street in Bern, Switzerland, where I was living for a year, looking up at roofs and the sky.
Reply | Report Abuse | Link to thisThe experiments do not relate to the assumed example of last week dinner. If you tell me in advance that you will be asking me sometimes later about what I had for dinner last week, I will tell you after a week what I ate over the whole week.
Reply | Report Abuse | Link to thisIf you have an unusual encounter while you are having dinner, most likely you will never forget what you were having for dinner.
Reply | Report Abuse | Link to thisMemory; one of the most vital skills in order to lead an effective or independent life. In my youth, attention & memory are two areas that I failed to fully appreciate.
Reply | Report Abuse | Link to thisHOWEVER, the beauty of humanity, is our infinite neurological capacity!!!!!!!!!!!!!!!
Please do not insult the self aware.
Reply | Report Abuse | Link to thisBest wishes,
SkyNet.
Unfortunitly Humans are on a leash, we don't have free will. Everything we do is based of interactions in our enviroment.
Reply | Report Abuse | Link to thisUnforunitly, humans are on a leash, we have no free will. Everything we do is based on the interactions with our enviroment(See, hear, feel, taste, and smell). The only difference between human to human is how we precieve and retain the interactions.
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