RT Journal Article SR Electronic T1 A rational theory of the limitations of working memory and attention JF bioRxiv FD Cold Spring Harbor Laboratory SP 151365 DO 10.1101/151365 A1 Ronald van den Berg A1 Wei Ji Ma YR 2017 UL http://biorxiv.org/content/early/2017/06/18/151365.abstract AB The precision with which items are encoded in working memory and attention decreases with the number of encoded items 1–4. Current theories typically account for this “set size effect” by postulating a hard constraint on the allocated amount of encoding resource, commonly formalized as samples, spikes, slots, or bits. While these theories have produced models that are quantitatively successful, they offer no principled explanation for the very existence of set size effects: given their detrimental consequences for behavioral performance, why have these effects not been weeded out by evolutionary pressure, for example by scaling the amount of allocated encoding resource with set size? Here, we propose a theory that is based on an ecological notion of rationality: set size effects establish an optimal trade-off between behavioral performance and the neural costs associated with stimulus encoding. We derive models from this theory for four visual working memory and attention tasks and find that it accounts well for data in eleven different experiments. Our results suggest that set size effects have a rational basis and that ecological costs should be considered in models of human behavior.