The Adaptive Nature of False Memories is Revealed by Gist-based Distortion of True Memories.

In addition to allowing us to remember objects and events that we have actually experienced, human memory systems are also subject to distortions, biases, and the creation of false memories. However, there are also potential benefits to our imperfect memory system: there are cases where memory distortion is actually adaptive, increasing the overall accuracy of memories. To examine one case where memory distortion might be adaptive, we had 24 participants view multiple real-world objects from a given category (10 airplanes, 10 backpacks…), and later recall the color of each object via a psychophysical adjustment task that allows us to examine both the variability of internal representations of color and the probability of forgetting an object's color altogether (see Brady et al. 2013, Psych. Science). According to a simple Bayesian analysis, the optimal response strategy in these circumstances involves systematic memory distortion: participants should report items' colors as closer to the mean color of the category than they were, since information from the category provides additional information above-and-beyond item-specific information. We found that participants were generally accurate, but even when they remembered having seen an item and remembered its color, they nevertheless reported the color as closer to the average color of its category than it really was (mean bias: 29°; t(23)=7.9, p< 0.0001). This bias remained even after accounting for the possibility that participants' guessed on some items using only category-based information. Thus, although participants' memories were systematically distorted, they were distorted in a way that is consistent with minimizing their average error according to a simple Bayesian analysis. This shows that memory distortion may not always be maladaptive: in some cases, distortion can result from a memory system that optimally combines information in the service of the broader goals of the person. Meeting abstract presented at VSS 2015.