How does working memory work? The manipulation unit of visual working memory

Abstract

What is the manipulation unit of visual working memory (VWM)? This is a key question to understand how the human mind updates the information absent in view to adapt to the ever-changing environment. We proposed two hypotheses: (a) the object-based hypothesis expects longer manipulating times when more objects are involved in manipulation, while (b) the Boolean-map-based hypothesis expects longer manipulating times when more Boolean maps are involved in manipulation. In Experiments 1 to 3, participants were asked to move, search, or dye a subset of stimuli (different numbers of orientations/objects, but all in one Boolean map) in VWM and then finish a change detection task. The results support the object-based hypothesis that participants’ manipulating times differed when manipulating different numbers of orientations although there was only one Boolean map all the time. In Experiment 4, two different colors linked together were presented on the same object (different Boolean maps) while two same colors were presented on different objects (same Boolean map). Participants were asked to dye a subset of stimuli into two different colors in VWM. The results showed that manipulating colors from one object (two different Boolean maps) was faster than that from two different objects (one Boolean map), supporting the object-based hypothesis. In conclusion, we adopted four novel manipulating tasks and found that objects are the elementary manipulation unit of VWM, instead of Boolean maps.