Perceptual limits on the visual monitoring task

A brief review is presented of recent work in vision science showing important limits on the ability of observers to carry out various tasks. First, it has been found that only a few moving items can be tracked at any time, even after considerable practice. Second, observers can often miss the appearance of unexpected objects or events, even if these are large. Third, observers can often miss changes that occur in front of them, even when these changes are large, repeated, and expected. Finally, observers simply cannot see two changes at a time, no matter how hard they try. The explanation for these effects is briefly discussed, along with the reasons why these limits are not usually noticed. Some suggestions are also given about what (if anything) can be done to mitigate their effects in regards to the visual monitoring task of the anesthesiologist.