How the Brain Makes Quick Decisions

"Our study is new in a few ways," he added. "We showed that implicit [short-term] memory can actually help you when recognition memory is being tested. People weren't sure it helped you pick which things you've seen before, so we were able to show that the unconscious type of memory can help."

Participants sat in front of a computer monitor as multicolored patterns flashed on the screen. Later, they were shown two images and asked to immediately identify which of the two images they had seen before, even if they had to guess. But it turned out that even when they thought they were guessing, they got the right answer most of the time, so they were doing more than guessing. They were also drawing on their short term, unconscious memory.

During parts of the experiment, participants were distracted from their visual assignment when they were ordered to remember a spoken number because they would have to identify it later. Distractions are known to impair the capture of long-term memories. We have to focus to remember well.

Help With Amnesia Patients

But that's when the surprise came.

"Remarkably, people were more accurate in selecting the image they had seen before" when asked to pick which of two images they had seen, Paller said. "They also were more accurate when they claimed to be guessing than when they registered some familiarity with the image."

It's not clear why the distraction helped instead of hindered. Paller suspects that one reason the distractions didn't hurt is that they involved the auditory system, not the visual system used in the recognition of colorful patterns. But that doesn't explain why people knew the answer when they thought they were guessing.

The real-world implications for this research are also unclear, at least at this time. Paller thinks it will be helpful in his long-term study of amnesia patients who retain some short-term memory but not long term. But will this really help Williams capture another trophy?

Maybe, if we understand it better, and that's the point of this kind of basic research. The work shows we have a tool we didn't know we had, a knowledge-based short-term memory that can be called upon for split-second decisions. That's a lot better than a guess.

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