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

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.)