Tripping Down Memory Lane – memory experiments

Tripping Down Memory Lane – memory experiments – Brief Article

Eric Haseltine

I WAS HOVERING OUTSIDE the lab last week, desperately trying to recall why I happened to be there at that moment, when I remembered I’d come to retrieve the book Memory: From Mind to Molecules, by Larry Squire and Eric Kandel.

All of us experience such moments of absentmindedness on occasion. Indeed, remembering which chore needs your attention or where you put the car keys can often be a hit-ormiss proposition. So why do we recall so precisely the details surrounding an assassination, marriage proposal, or the birth of a child? And what goes on in the brain to imprint memories in the first place?

Neuroscientists haven’t fully answered these questions, but they’ve had tantalizing glimpses of how the process of remembering something works. One thing they’ve learned is that information gets stashed in two very distinct types of memory on its way to permanently lodging in yet a third kind of memory.

EXPERIMENT 1

Stare at this figure, then shut your eyes, paying close attention to the afterimage.

The faithful shapes and colors you see for an instant are the first stage of memory, sensory storage, which gets its name from its nearly perfect reproduction of sensory information flowing into the brain.

EXPERIMENT 2

Scan these icons from left to right, glancing at each one once. Turn away and list as many as you can.

You probably remember icons on the right best because the second stage of memory, working storage, has so little capacity that images viewed early in a sequence can get pushed out to make room for those arriving later. Psychologists call this retroactive interference. You might have also noticed that icons at the beginning of the list stayed with you better than those in the middle. That’s because proactive interference causes data already in working memory to hinder the storage of information coming in later. Because the first images in working memory suffer only retroactive interference, they’re retrieved better than the unfortunate icons in the middle, which get hammered both proactively and retroactively.

With this constant war between proactive and retroactive interference, how does working information ever find its way into the third kind of memory, long-term storage? Neuroscientists believe that working memories are stored as sustained electrical discharges in nerve cells that respond to sensory information. These electric echoes keep sensations around for several seconds after the events producing them have gone away. If the neural reverberations are strong enough, they can actually alter the physical structure of nerve cells and in the process create permanent memories. Neurons change in this way either through repetition–for example, writing down someone’s phone number over and over again–or by association with strong emotions that crank up the brain’s electrical volume and produce vivid recollections of major life events. The process is analogous to etching a groove in a piece of hardwood either by scratching many times with a dull knife or taking one good whack with a meat cleaver.

EXPERIMENT 3

Take a break for a few minutes. When you come back, we’ll learn something about long-term memory. Welcome back. Now, see how many of these icons you recognize from Experiment 2.

You probably got most of the repeated icons even though they were all from the middle of the list in Experiment 2 and therefore buffeted by both proactive and retroactive interference. The reason is that there are two ways of measuring long-term memory: recall and recognition. Recall memory actively dredges up specific information, whereas recognition memory only passively acknowledges whether a thing has been seen before. Brain researchers aren’t certain why, but information makes the perilous transition from working memory into long-term recognition far easier than it does to long-term recall. If you try this experiment again a few days from now, you’ll still be able to recognize icons from the original group, which means they’ve lodged in long-term memory and have changed the very structure of your brain. In a literal sense, you are what you read.

BOGGLERS SOLUTIONS

QUEENS AT PEACE

1. Nathan Cappallo found this symmetrical solution.

2. This symmetrical solution was found by Nick Baxter.

3. Can you find a better solution?

4. This solution was found by Nick Baxter.

QUADRILATERAL THINKING

1. D and J. A parallelogram always has opposite angles of equal measure.

2. The two types of quadrilaterals that can be concave are C (Kite), and L (one pair of opposite sides of equal length).

3. K (one pair of 90-degree opposite argles) is a subclass of B (Cyclic quadrilateral: All corners lie on a single circle), which is in turn a subclass of A (Convex). As shown in the diagram below, any quadrilateral of class K is composed of two right triangles, and the right-angle vertex of a right triangle always lies on the semicircle whose diameter is the hypotenuse of the right triangle.

4. H (Square), G (Rhombus) or F (Rectangle), D (Parallelogram), I (Trapezoid), A (Convex), E (Quadrilateral). Can you find any other solutions?

5. C (Kite), I (Trapezoid), L (one pair of opposite sides of equal length), and K (one pair of opposite angles both 90 degrees) or B (Cyclic).

TOUCHY SUBJECT

1. Two layers of three sheets each. For clarity, the top layer is shown with outlines.

2. Nine. Three layers of three sheets each. The central area is shown enlarged for detail. This solution is similar to the solution for problem 1, except that a new layer has been inserted between the top and bottom layers, with pieces opened up a little to allow the top layer to touch the bottom layer.

3. An unlimited number, fanned like a deck of cards at gradually increasing angles. If you have already arranged five sheets of paper in a fan, as shown above, add the sixth sheet in the position indicated by the red outline. Notice that the sixth sheet touches all of the previous five sheets. This solution was found by Karl Schaffer.

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