Free How We Learn by Benedict Carey Page B

provided the categories. When the ninety seconds were up, the papers were taken away.
    Four hours later, when the effects of the drug had worn off, the participants returned to the lab and had another smoke. Some who’d been given a real joint the first time got a placebo this time around, and vice versa. Others smoked the same type both times. Twenty minutes later, without further study, they took a test.
    Some got a free recall test, writing down as many of the words as they could remember in six minutes. Others took a “cued recall” test, in which they saw the list of categories (“A type of vehicle”) and filled in as many of the words in that category as they could. And sure enough—on the free recall—those who’d smoked a real joint on both occasions remembered 40 percent more than those who got a real one to study and a placebo for the test. The reverse was also true to a lesser extent: Those who initially studied on the placebo joint didbetter after smoking another placebo, compared to a real joint. The participants’ memories functioned best when their brain was in the same state during study as during testing, high or not high.
    Why? The cued-recall test (the one with the categories) helped provide an answer. The scores on this test were uniformly high, no matter what the students smoked or when. This finding suggests that the brain stores roughly the same number of words when moderately high as when not—the words are in there, either way. Yet it must organize them in a different way for later retrieval. That “retrieval key” comes back most clearly when the brain is in the same state, stoned or sober. The key becomes superfluous, however, when the categories are printed right there on the page. There’s no need for it, because an external one is handy. As the authors wrote, “The accessibility of retrieval cues which have been encoded in drug associated state—such as that produced by a moderate dose of marijuana—appears to depend, in part, on restoration of that state atthe time of desired recall.”
    The joint-placebo study also gives us an idea how strong these internal, drug-induced memory cues are. Not so strong. Give someone a real hint—like a category name—and it easily trumps the internal cues. The same thing turned out to be true for alcohol and other drugs that these researchers and others eventually studied: Internal and external cues can be good reminders, but they pale next to strong hints.
    The personality of the learning brain that emerges from all this work on external and internal cues is of a shifty-eyed dinner companion. It is tracking the main conversation (the homework assignment, the music notation, the hard facts) and occasionally becoming engaged in it. At the same time, it’s also periodically having a quick look around, taking in the room, sketching in sights and sounds and smells, as well as noting its internal reactions, its feelings and sensations. These features—the background music, a flickering candle, apang of hunger—help our companion recall points made during the conversation later on, especially when the topic is a new one. Still, a strong hint is better.
    I think about this, again, in terms of the geometric proof of the Pythagorean theorem. Summoning up that late night scene in the math building three decades ago, I can begin to reconstruct the proof, but as I said it takes some futzing to get the triangles in place. However, if someone sketches out just part of the drawing, it all comes back immediately. The strong hint provided by a partial drawing trumps the weaker ones provided by reinstating my learning environment.
    In a world that provided strong hints when needed, this system would be ideal. Just as it would be wonderful if, whenever we had to perform on some test, we could easily re-create the precise environment in which we studied, piping in the same music that was playing, dialing up the same afternoon light, the same mental state—all