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

Why, if evolution is usually so good at making things work well, is our memory so hit-or-miss?

The question becomes especially pointed when we compare the fragility of our memory with the robustness of the memory in the average computer. Whereas my Mac can store (and retrieve) my complete address book, the locations of all the countries in Africa, the complete text of every email message I ever sent, and all the photographs I've taken since late 1999 (when I got my first digital camera), not to mention the first 3,000 digits of pi, all in perfect detail, I still struggle with the countries in Africa and can scarcely even remember whom I last emailed, let alone exactly what I said. And I never got past the first ten digits of pi (3.1415926535) — even though I was just the sort of nerd who'd try to memorize more.*

Human memory for photographic detail is no better; we can

*Which is not to say that no human being could do better. A number of people, far more dedicated to the cause than I ever was, have managed to learn thousands, even tens of thousands, of digits. But it takes years. I'd rather go hiking. Still, if you are into that sort of thing, refer to http://www.ludism.org/mentat/PiMemorisation for some basic tips.

recognize the main elements of a photo we've seen before, but studies show that people often don't notice small or even fairly large changes in the background.* And I for one could never ever recall the details of a photograph, no matter how long I sat and stared at it beforehand. I can still remember the handful of phone numbers I memorized as a child, when I had loads of free time, but it took me almost a year to learn my wife's cell phone number by heart.

Worse, once we do manage to encode a memory, it's often difficult to revise it. Take, for instance, the trouble I have with the name of my dear colleague Rachel. Five years after she got divorced and reverted to her maiden name (Rachel K.), I still sometimes stumble and refer to her by her former married name (Rachel C.) because the earlier habit is so strong. Whereas computer memory is precise, human memory is in many ways a recalcitrant mess.

Computer memory works well because programmers organize information into what amounts to a giant map: each item is assigned a specific location, or "address," in the computer's databanks. With this system, which I will call "postal-code memory," when a computer is prompted to retrieve a particular memory, it simply goes to the relevant address. (A 64-megabyte memory card holds roughly 64 million such addresses, each containing a single "word" made up of a set of eight binary digits.)

Postal-code memory is as powerful as it is simple; used properly, it allows computers to store virtually any information with near-perfect reliability; it also allows a programmer to readily change any memory; no referring to Rachel K. as Rachel C. once she's changed her name. It's no exaggeration to say that postal-code memory is a key component of virtually every modern computer.

But not, alas, in humans. Having postal-code memory would

*Google for "change blindness" if you've never seen a demonstration; if you haven't seen Derren Brown's "person swap" video on YouTube (www.youtube.com/watch?v= CFaY3YcMgiT), you're missing something special.

have been terrifically useful for us, but evolution never discovered the right part of the mountain range. We humans rarely — if ever — know precisely where a piece of information is stored (beyond the extremely vague "somewhere inside the brain"), and our memory evolved according to an entirely different logic.