How many locations can be selected at once?

The visual system uses several tools to select only the most relevant visual information for further processing, including selection by location. In the present study, the authors explored how many locations can be selected at once. Although past evidence from several visual tasks suggests that the visual system can operate on a fixed number of 4 objects or locations at once, the authors found that this capacity varies widely in response to the precision of selection required by the task. When the authors required precise selection regions, only 2-3 locations could be selected. But when the selection regions could be coarser, up to 6-7 locations could be selected. The authors discuss potential mechanisms underlying the selection of multiple locations and review the evidence for fixed limits in visual attention.