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

A good, scientifically well documented illustration of how vulnerable autobiographical memory can be took place in 1992, courtesy of the ever-mercurial Ross Perot, an iconoclastic billionaire from Texas who ran for president as an independent candidate. Perot initially attracted a strong following, but suddenly, under fire, he withdrew from the race. At that point an enterprising psychologist named Linda Levine asked Perot followers how they felt about his withdrawal from the campaign. When Perot subsequently reentered the race, Levine had an unanticipated chance to collect follow-up data. Soon after election day, Levine asked people whom they voted for in the end, and how they felt about Perot earlier in the campaign, at the point when he had dropped out. Levine found that people's memory of their own feelings shifted. Those who returned to Perot when Perot reentered the race tended to whitewash their negative memories of his withdrawal, forgetting how betrayed they had felt, while people who moved on from Perot and ultimately voted for another candidate whitewashed their positive memories of him, as if they had never intended to vote for him in the first place. Orwell would have been proud.*

Distortion and interference are just the tip of the iceberg. Any number of things would be a whole lot easier if evolution had simply vested us with postal-code memory. Take, for example, the seemingly trivial task of remembering where you last put your house keys. Nine

^Several other studies have pointed to the same conclusion — we all tend to be historical revisionists, with a surprisingly dodgy memory of our own prior attitudes. My own personal favorite is an article called "From Chump to Champ" — it describes the one instance in which we all are happy to endure ostensibly negative memories about our own past: when it helps paint us, Rocky-style, as triumphing over adversity.

times out of ten you may get it right, but if you should leave your keys in an atypical spot, all bets are off. An engineer would simply assign a particular memory location (known as a "buffer") to the geographical coordinates of your keys, update the value whenever you moved them, and voilא: you would never need to search the pockets of the pants you wore yesterday or find yourself locked out of your own home.

Alas, precisely because we can't access memories by exact location, we can't straightforwardly update specific memories, and we can't readily "erase" information about where we put our keys in the past. When we place them somewhere other than their usual spot, recency (their most recent location) and frequency (where they're usually placed) come into conflict, and we may well forget where the keys are. The same problem crops up when we try to remember where we last put our car, our wallet, our phone; it's simply part of human life. Lacking proper buffers, our memory banks are a bit like a shoebox full of disorganized photographs: recent photos tend on average to be closer to the top, but this is not guaranteed. This shoebox-like system is fine when we want to remember some general concept (say, reliable locations for obtaining food) — in which case, remembering any experience, be it from yesterday or a year ago, might do. But it's a lousy system for remembering particular, precise bits of information.

The same sort of conflict between recency and frequency explains the near-universal human experience of leaving work with the intention of buying groceries, only to wind up at home, having completely forgotten to stop at the grocery store. The behavior that is common practice (driving home) trumps the recent goal (our spouse's request that we pick up some milk).

Preventing this sort of cognitive autopilot should have been easy. As any properly trained computer scientist will tell you, driving home and getting groceries are goals, and goals belong on a stack. A computer does one thing, then a user presses a key and the first goal (analogous to driving home) is temporarily interrupted by a new goal (getting groceries); the new goal is placed on top of the stack (it becomes top priority), until, when it is completed, it is removed from the stack, returning the old goal to the top. Any number of goals can then be pursued in precisely the right priority sequence. No such luck for us human beings.