Variable search for orientation, uniformly optimal search for identity

We compare eye movement strategies across a range of different stimulus sets to testthe prediction that eye movements are guided by expected information gain. Whensearching for a simple target that has been defined based on orientation, inter-individual variability is high, and a large proportion of eye movements are directed tolocations where peripheral vision would have been sufficient to determine whether thetarget was present there or not. In contrast, when searching for a target defined basedon identity, eye movements are similar across individuals and highly efficient, beingdirected almost exclusively to the locations where central vision is most needed. Theresults suggest that for most people, the way they search for a simple feature(orientation) is not directly representative of the way they search for objects based ontheir identity. More generally, the results highlight that because humans are adaptable,contradictory theories can be accurate descriptions of search in particular contexts andindividuals. For a complete and accurate account of human search behaviour to beachieved, the conditions that shift us from one mode of behaviour to another need to bepart of our models.