Visual long-term memory has the same limit on fidelity as visual working memory.
Visual long-term memory can store thousands of objects with surprising visual detail, but just how detailed are these representations and how can we quantify this fidelity? Using the property of color as a case study, we estimated the precision of visual information in long-term memory, and compared this to the precision of the same information in working memory. Observers were shown real-world objects in a random color, and then ask to recall the color after a delay. We quantified two parameters of performance: the variability of internal representations of color (fidelity) and the probability of forgetting an object's color altogether. Surprisingly, the data show that the fidelity of color information in long-term memory was comparable to the asymptotic precision of working memory. These results suggest that a common limit may constrain both long-term memory and working memory, such as a bound on the fidelity required to retrieve memory representations.