String editing analysis of human visual search

Eye movement (EM) data were recorded for human subjects performing a visual search task in a stereoscopic computer-generated three-dimensional scene. Each experimental run consisted of six presentations: three different object placements on a common background (quasi-natural scene) were used and one of the placements was repeated three additional times. Raw EM searchpath data were linearized, fixation points were defined via a fixation algorithm and, finally, strings of fixation region labels were obtained based upon a priori regionalization schemes. Use of string editing techniques allowed quantitative comparison of the similarity of various searchpaths. Analysis of the similarity of searchpaths for each subject, as well as across subjects, led us to conclude that presentation of repeated object placements caused each subject to develop a partly self-consistent, but idiosyncratic searchpath based upon a spatial model for that placement pattern.