Selective Visual Attention: Computational Models and Applications

2.3 Guided Search Theory

Another influential idea, Wolfe et al.'s proposal called guided search (GS), has been proposed as an extension of the FIT. It has eliminated the deficiency of the standard FIT and captured a wide range of search behaviours [55–61]. Similar to the use before, the term ‘search' refers to scanning the environment in order to find a target in a scene no matter whether the target exists or not. Hence, the GS theory is implemented from the perspective of target search in input visual field. The main differences between the standard FIT and GS can be stated as follows. (1) In FIT, the two stages, pre-attention (or feature registration) in parallel and attention (or feature integration) in serial are processed almost separately. Very little information from the parallel pre-attention stage influences the next serial attention stage in conjunction cases. Two of main results are: 1) searching a conjunctional target is very slow and its RT increases with detractor size; 2) target-absent (negative) search requires double RT compared to the target-present (positive) search. In the standard FIT experiments, the subjects did not know what to look for, so there is no guidance from the parallel pre-attention stage for the serial search stage. In fact, the linear ascended (RT vs. size) function of conjunctional search and the 2 : 1 ratio in slopes between negative and positive searches are not valid in some trials. GS theory gives some experimental results to confirm that ...