ABSTRACT
Evidence for qualitatively different processes involved in the coding of simple features and of feature conjunctions comes from studies of visual search. When targets have a unique distinguishing feature relative to distractors (i.e. with what we will term single-feature targets), the function for reaction times (RTs) relative to the number of distractors is non-linear or even flat. In contrast,search times for targets defined by a combination of features (i.e. combined-feature targets) characteristically increase linearly as the number of distractors increases. Furthermore, in the prototypical case, the slope for target-present decisions is about half that for absent decisions. The linear search functions and 1 : 2 present-absent slope ratios have been taken as indicative of serial, selfterminating search (Treisman and Gelade, 1980).
