Kluge: The Haphazard Construction of the Human Mind (Houghton Mifflin; 2008)

electric light to perform well, the scuba divers were better at remembering the words they studied underwater when they were tested underwater (relative to being tested on land) — a fact that strikes this landlubber as truly amazing. Just about every time we remember anything, context looms in the background.*

This is not always a good thing. As Merlin Mann of the blog '43 folders' put it, the time when we tend to notice that we need toilet paper tends not to be the moment when we are in a position to buy it. Relying on context works fine if the circumstance in which we need some bit of information matches the circumstance in which we first stored it — but it becomes problematic when there is a mismatch between the original circumstance in which we've learned something and the context in which we later need to remember it.

Another consequence of contextual memory is the fact that nearly every bit of information that we hear (or see, touch, taste, or smell), like it or not, triggers some further set of memories — often in ways that float beneath our awareness. The novelist Marcel Proust, who coined the term 'involuntary memory,' got part of the idea — the

* Similarly, if you study while stoned, you might as well take the test while stoned. Or so I have been told.

reminiscences in Proust's famous (and lengthy) novel Remembrance of Things Past were all triggered by a single, consciously recognized combination of taste and smell.

But the reality of automatic, unconscious memory exceeds even that which Proust imagined; emotionally significant smells are only the tip of an astonishing iceberg. Take, for example, an ingenious study run by a former colleague of mine, John Bargh, when he was at New York University. His subjects, all undergraduates, were asked to unscramble a series of sentences. Quietly embedded within the scrambled lists were words related to a common theme, such as old, wise, forgetful, and Florida, designed to elicit the concept of the elderly. The subjects did as they were told, diligently making their way through the task. The real experiment, however, didn't begin until afterward, when Bargh surreptitiously videotaped subjects as they departed after the test, walking to an elevator down the hall. Remarkably, the words people read affected their walking speed. The subjects all presumably had places to go and people to see, but those who unscrambled words like retired and Florida ambled more slowly than those who hadn't.

Another lab studied people as they played a trivia game. Those briefly primed by terms like professor or intelligent outperformed those prepped with less lofty expressions, such as soccer hooligans and stupid. All the trash-talking that basketball players do might be more effective than we imagine.

At first, these studies may seem like mere fun and games — stupid pet tricks for humans — but the real-life consequences of priming can be serious. For example, priming can lead minority groups to do worse when cultural stereotypes are made especially salient, and, other things being equal, negative racial stereotypes tend to be primed automatically even in well-intentioned people who report feeling 'exactly the same' about whites and blacks. Likewise, priming may reinforce depression, because being in a bad mood primes a person to think about negative things, and this in turn furthers depression. The context-driven nature of memory may also play a role in leading depressed people to seek out depressive activities, such as drinking or listening to songs of lost love, which presumably deepens the gloom as well. So much for intelligent design.

Anchoring our memories in terms of context and cues, rather than specific pre-identified locations, leads to another problem: our memories often blur together. In the first instance, this means that something I learn now can easily interfere with something I knew before: today's strawberry yogurt can obscure yesterday's raspberry. Conversely, something I already know, or once knew, can interfere with something new, as in my trouble with acclimating to Rachel K.'s change in surname.

Ultimately, interference can lead to something even worse: false memories. Some of the first direct scientific evidence to establish the human vulnerability to false memories came from a now classic cognitive-psychology study in which people were asked to memorize a series of random dot patterns like these:

Later, the experimenters showed various dot patterns to the same subjects and asked whether they had seen certain ones before. People were often tricked by this next one, claiming they had seen it when in fact it is a new pattern, a sort of composite of the ones viewed previously.

We now know that these sorts of 'false alarms' are common. Try, for example, to memorize the following list of words: bed, rest, awake, tired, dream, wake, snooze, blanket, doze, slumber, snore, nap, peace, yawn, drowsy, nurse, sick, lawyer, medicine, health, hospital, dentist, physician, ill, patient, office, stethoscope, surgeon, clinic, cure.

If you're like most people, you'll surely remember the categories of words I've just asked you to memorize, but you'll probably find yourself fuzzy on the details. Do you recall the word dream or sleep (or both, or neither?), snooze or tired (or both, or neither)? How about doctor or dentist⁷. Experimental data show that most people are easily flummoxed, frequently falling for words they didn't see (such as doctor). The same thing appears to happen even with so-called flashbulb memories, which capture events of considerable importance, like 9/11 or the fall of the Berlin Wall. As time passes, it becomes harder and harder to keep particular memories straight, even though we continue to believe, sometimes with great confidence, that they are accurate. Sadly, confidence is no measure of accuracy.

For most species, most of the time, remembering gist rather than detail is enough. If you are a beaver, you need to know how to build dams, but you don't need to remember where each individual branch is. For most of evolution, the costs and benefits of context-dependent memory worked out fine: fast for gist, poor for detail; so be it.

If you are human, though, things are often different; societies and circumstances sometimes require of us a precision that wasn't demanded of our ancestors. In the courtroom, for example, it's not enough to know that some guy committed a crime; we need to know which guy did — which is often more than the average human can remember. Yet, until recently, with the rise of DNA evidence, eyewitness testimony has often been treated as the final arbiter; when an honest-looking witness appears confident, juries usually assume that this person speaks the truth.

Such trust is almost certainly misplaced — not because honest people lie, but because even the most honorable witness is just human— saddled with contextually driven memory. Oodles of evidence for this comes from the lab of the psychologist Elizabeth Loftus. In a typical study, Loftus shows her subjects a film of a car accident and asks them afterward what happened. Distortion and interference rule the day. For example, in one experiment, Loftus showed people slides of a car running a stop sign. Subjects who later heard mention of a yield sign would often blend what they saw with what they heard and misremember the car as driving past a yield sign rather than a stop sign.