The speed limits of memory

As anyone who has tried to memorize a one-hundred-digit number can attest, acquisition of numerical information typically proceeds at less than one bit/s. If human memory operated at this speed in general, even a simple conversation would not be possible. Indeed, through techniques such as the memory palace, which translate numerical information into more natural contexts, memory athletes manage considerably higher rates. This suggests that memory, in its intended environment and under training, performs at substantial speed, which can be quantified in memory competitions. Analyzing the data reveals three phenomena. First, in short-duration tasks up to 42 bit/s have been achieved. Remarkably, competitors spend most of the time on reading, indicating that they form mental associations even more rapidly. Second, record performances show a remarkable concordance across time scales: the processing speed depends on memorization time as a power law. Third, despite dramatic improvements in scores and mnemonic strategies over the last decades, the differences in information rates across memorization tasks remain remarkably consistent.