Memory versus Perceptual-Motor Tradeoffs in a Blocks World Task

Using information in-the-world as external memory may be a low-cost alternative to internal memory: storage is free, and retrieval is often quick (involving a saccade) and reliable. However, when the cost of accessing external information increases, in-the-head storage and retrieval may become the least-cost solution. We employ the rational analysis framework (Anderson, 1990) to study the effect of varying the cost of information access on interactive behavior. Increasing the cost of information access induced a switch from information in-the-world (the perceptualmotor strategy) to information in-the-head (the memory strategy). Given the effort and unreliability of internal storage, the threshold for switching from an in-the-world to an in-the-head strategy is surprisingly low.