Archive for March, 2009

How I wish I knew where Nathan stashed that deck.

Like many people, I can never remember a joke. I hear or read something hilarious, I laugh loudly enough to embarrass everybody else in the library, and then I instantly forget everything about it — everything except the fact, always popular around the dinner table, that “I heard a great joke today, but now I can’t remember what it was.”

For researchers who study memory, the ease with which people forget jokes is one of those quirks, those little skids on the neuronal banana peel, that end up revealing a surprising amount about the underlying architecture of memory.

And there are plenty of other similarly illuminating examples of memory’s whimsy and bad taste — like why you may forget your spouse’s birthday but will go to your deathbed remembering every word of the “Gilligan’s Island” theme song. And why you must chop a string of data like a phone number into manageable and predictable chunks to remember it and will fall to pieces if you are in Britain and hear a number read out as “double-four, double-three.” And why your efforts to fill in a sudden memory lapse by asking your companions, “Hey, what was the name of that actor who starred in the movie we saw on Friday?” may well fail, because (what useless friends!) now they’ve all forgotten, too.

Welcome to the human brain, your three-pound throne of wisdom with the whoopee cushion on the seat.

In understanding human memory and its tics, Scott A. Small, a neurologist and memory researcher at Columbia, suggests the familiar analogy with computer memory.

We have our version of a buffer, he said, a short-term working memory of limited scope and fast turnover rate. We have our equivalent of a save button: the hippocampus, deep in the forebrain is essential for translating short-term memories into a more permanent form.

Our frontal lobes perform the find function, retrieving saved files to embellish as needed. And though scientists used to believe that short- and long-term memories were stored in different parts of the brain, they have discovered that what really distinguishes the lasting from the transient is how strongly the memory is engraved in the brain, and the thickness and complexity of the connections linking large populations of brain cells. The deeper the memory, the more readily and robustly an ensemble of like-minded neurons will fire.

This process, of memory formation by neuronal entrainment, helps explain why some of life’s offerings weasel in easily and then refuse to be spiked. Music, for example. “The brain has a strong propensity to organize information and perception in patterns, and music plays into that inclination,” said Michael Thaut, a professor of music and neuroscience at Colorado State University. “From an acoustical perspective, music is an overstructured language, which the brain invented and which the brain loves to hear.”

A simple melody with a simple rhythm and repetition can be a tremendous mnemonic device. “It would be a virtually impossible task for young children to memorize a sequence of 26 separate letters if you just gave it to them as a string of information,” Dr. Thaut said. But when the alphabet is set to the tune of the ABC song with its four melodic phrases, preschoolers can learn it with ease.

And what are the most insidious jingles or sitcom themes but cunning variations on twinkle twinkle ABC?

Really great jokes, on the other hand, punch the lights out of do re mi. They work not by conforming to pattern recognition routines but by subverting them. “Jokes work because they deal with the unexpected, starting in one direction and then veering off into another,” said Robert Provine, a professor of psychology at the University of Maryland, Baltimore County, and the author of “Laughter: A Scientific Investigation.” “What makes a joke successful are the same properties that can make it difficult to remember.”

This may also explain why the jokes we tend to remember are often the most clichéd ones. A mother-in-law joke? Yes, I have the slot ready and labeled.

Memory researchers suggest additional reasons that great jokes may elude common capture. Daniel L. Schacter, a professor of psychology at Harvard and the author of “The Seven Sins of Memory,” says there is a big difference between verbatim recall of all the details of an event and gist recall of its general meaning.

“We humans are pretty good at gist recall but have difficulty with being exact,” he said. Though anecdotes can be told in broad outline, jokes live or die by nuance, precision and timing. And while emotional arousal normally enhances memory, it ends up further eroding your attention to that one killer frill. “Emotionally arousing material calls your attention to a central object,” Dr. Schacter said, “but it can make it difficult to remember peripheral details.”

As frustrating as it can be to forget something new, it’s worse to forget what you already know. Scientists refer to this as the tip-of-the-tongue phenomenon, when you know something but can’t spit it out, and the harder you try the more noncompliant the archives.

It’s such a virulent disorder that when you ask friends for help, you can set off so-called infectious amnesia. Behind the tying up of tongues are the too-delicate nerves of our brain’s frontal lobes and their sensitivity to anxiety and the hormones of fight or flight. The frontal lobes that rifle through stored memories and perform other higher cognitive tasks tend to shut down when the lower brain senses danger and demands that energy be shunted its way.

For that reason anxiety can be a test taker’s worst foe, and the anxiety of a pop quiz from a friend can make your frontal lobes freeze and your mind go blank. That is also why you’ll recall the frustratingly forgotten fact later that night, in the tranquillity of bed.

Memories can be strengthened with time and practice, practice, practice, but if there’s one part of the system that resists improvement, it’s our buffers, the size of our working memory on which a few items can be temporarily cached. Much research suggests that we can hold in short-term memory only five to nine data chunks at a time.

The limits of working memory again encourage our pattern-mad brains, and so we strive to bunch phone numbers into digestible portions and could manage even 10-digit strings when they had area codes with predictable phrases like a middle zero or one. But with the rise of atonal phone numbers with random strings of 10 digits, memory researchers say the limits of working memory have been crossed. Got any index cards?