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Weiwei Zhang, Steven Luck; Sudden death for overtime memories. Journal of Vision 2008;8(6):210. doi: https://doi.org/10.1167/8.6.210.
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Although the brain has a system for storing some kinds of memories for a lifetime, it also maintains temporary, disposable, scratch-pad memories. Do these short-term memories simply fade away as they age? Or do they die a sudden death? For decades, researchers have concluded that visual short-term memories decay gradually, becoming less and less precise as they are retained for longer periods of time. However, results of this sort could alternatively result from a progressive increase in the probability that the memory has completely terminated.
In the present study, we used a short-term color recall paradigm in which subjects attempted to retain three sample items in short-term memory. After a delay of 1, 4, or 10 seconds, one of the three items was probed, and the observers attempted to report its color by clicking on a color wheel. The resulting data set consisted of a distribution of memory errors at each delay period. From this distribution, we used maximum likelihood estimation to extract the precision of the memory representation (which should decline over time if the memories decay) and the probability that any information at all remains in short-term memory (which should decline over time if the memories suddenly terminate). We found that visual short-term memories suffered no significant loss of strength or precision over a period of time. Instead, these memories suddenly terminated, disappearing without a trace. These results suggest that active maintenance in short-term memory is an all-or-none process, in which a representation is maintained over time with no loss of resolution until it is suddenly lost.
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