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

For something that happened fairly recently, we can get around the problem by using a simple rule of thumb: the more recent the event, the more vivid the memory. But this vividness has its limits: events that have receded more than a couple of months into the past tend to blur together, frequently leaving us chronologically challenged. For example, when regular viewers of the weekly TV news

Th e principals involved were Tonya Harding, Jeff Gillooly (her ex-husband), and Nancy Kerrigan; Gillooly's hired goon went after Kerrigan's knee on January 6,1994. Bonus question: When did the Rwandan genocide begin? Answer: April of that same year, three months after the onset of Tonyagate, which was still a big enough story to obscure the news from Rwanda. In the words of the UN commander on the scene, Rom?o Dallaire, 'During the 100 days of the Rwanda genocide, there was more coverage of Tonya Harding by ABC, CBS, and NBC than of the genocide itself.'

program 60 Minutes were asked to recall when a series of stories aired, viewers could readily distinguish a story presented two months earlier from a story shown only a week before. But stories presented further in the past — say, two years versus four — all faded into an indistinct muddle.

Of course, there is always another workaround. Instead of simply trying to recall when something happened, we can try to infer this information. By a process known as 'reconstruction,' we work backward, correlating an event of uncertain date with chronological landmarks that we're sure of. To take another example ripped from the headlines, if I asked you to name the year in which O. J. Simpson was tried for murder, you'd probably have to guesstimate. As vivid as the proceedings were then, they are now (for me, anyway) beginning to get a bit hazy. Unless you are a trivia buff, you probably can't remember exactly when the trial happened. Instead, you might reason that it took place before the Monica Lewinsky scandal but after Bill Clinton took office, or that it occurred before you met your significant other but after you went to college. Reconstruction is, to be sure, better than nothing, but compared to a simple time/date stamp, it's incredibly clumsy.

A kindred problem is reminiscent of the sixth question every reporter must ask. Not who, what, when, where, or why, but how, as in How do I know it? What are my sources? Where did I see that somewhat frightening article about the Bush administration's desire to invade Iran? Was it in The New Yorker? Or the Economist? Or was it just some paranoid but entertaining blog? For obvious reasons, cognitive psychologists call this sort of memory 'source memory.' And source memory, like our memory for times and dates, is, for want of a proper postal code, often remarkably poor. One psychologist, for example, asked a group of test subjects to read aloud a list of random names (such as Sebastian Weisdorf). Twenty-four hours later he asked them to read a second list of names and to identify which ones belonged to famous people and which didn't. Some were in fact the names of celebrities, and some were made up; the interesting thing is that some were made-up names drawn from the first list. If people had good source memory, they would have spotted the ruse. Instead, most subjects knew they had seen a particular name before, but they had no idea where. Recognizing a name like Sebastian Weisdorf but not recalling where they'd seen it, people mistook Weisdorf for the name of a bona fide celebrity whom they just couldn't place. The same thing happens, with bigger stakes, when voters forget whether they heard some political rumor on Letterman or read it in the New York Times.

The workaround by which we 'reconstruct' memory for dates and times is but one example of the many clumsy techniques that humans use to cope with the lack of postal-code memory. If you Google for 'memory tricks,' you'll find dozens more.

Take for example, the ancient 'method of loci.' If you have a long list of words to remember, you can associate each one with a specific room in a familiar large building: the first word with the vestibule, the second word with the living room, the third word with the dining room, the fourth with the kitchen, and so forth. This trick, which is used in adapted form by all the world's leading mnemonists, works pretty well, since each room provides a different context for memory retrieval — but it's still little more than a Band-Aid, one more solution we shouldn't need in the first place.

Another classical approach, so prominent in rap music, is to use rhyme and meter as an aid to memorization. Homer had his hexameter, Tom Lehrer had his song 'The Elements' ('There's antimony, arsenic, aluminum, selenium, / And hydrogen and oxygen and nitrogen and rhenium . . .'), and the band They Might Be Giants have their cover of 'Why Does the Sun Shine? (The Sun Is a Mass of Incandescent Gas).'

Actors often take these mnemonic devices one step further. Not only do they remind themselves of their next lines by using cues of rhythm, syntax, and rhyme; they also focus on their character's motivations and actions, as well as those of other characters. Ideally, this takes place automatically. In the words of the actor Michael Caine, the goal is to get immersed in the story, rather than worry about specific lines. 'You must be able to stand there not thinking of that line. You take it off the other actor's face.' Some performers can do this rather well; others struggle with it (or rely on cue cards). The point is, memorizing lines will never be as easy for us as it would be for a computer. We retrieve memorized information not by reading files from a specific sector of the hard drive but by cobbling together as many clues as possible — and hoping for the best.

Even the oldest standby — simple rehearsal, repeating something over and over — is a bit of clumsiness that shouldn't be necessary. Rote memorization works somewhat well because it exploits the brain's attachment to memories based on frequently occurring events, but here too the solution is hardly elegant. An ideal memory system would capture information in a single exposure, so we wouldn't have to waste time with flash cards or lengthy memorization sessions. (Yes, I've heard the rumors about the existence of photographic memory, but no, I've never seen a well-documented case.)

There's nothing wrong with mnemonics and no end to the possibilities; any cue can help. But when they fail, we can rely on a different sort of solution — arranging our life to accommodate the limits of our memory. I, for example, have learned through long experience that the only way to deal with my congenital absent-mindedness is to develop habits that reduce the demands on my memory. I always put my keys in the same place, position anything I need to bring to work by the front door, and so forth. To a forgetful guy like me, a PalmPilot is a godsend. But the fact that we can patch together solutions doesn't mean that our mental mechanisms are well engineered; it is a symptorn of the opposite condition. It is only the clumsiness of human memory that necessitates these tricks in the first place.

Given the liabilities of our contextual memory, it's natural to ask whether its benefits (speed, for example) outweigh the costs. I think not, and not just because the costs are so high, but because it is possible in principle to have the benefits without the costs. The proof is Google (not to mention a dozen other search engines). Search engines start with an underlying substrate of postal-code memory (the well-mapped information they can tap into) and build contextual memory on top. The postal-code foundation guarantees reliability, while the context on top hints at which memories are most likely needed at a given moment. If evolution had started with a system of memory organized by location, I bet that's exactly what we'd have, and the advantages would be considerable. But our ancestors never made it to that part of the cognitive mountain; once evolution stumbled upon contextual memory, it never wandered far enough away to find another considerably higher peak. As a result, when we need precise, reliable memories, all we can do is fake it — kluging a poor man's approximation of postal-code memory onto a substrate that doesn't genuinely provide for it.

In the final analysis, we would be nowhere without memory; as Steven Pinker once wrote, 'To a very great extent, our memories are ourselves.' Yet memory is arguably the mind's original sin. So much is built on it, and yet