Conjunction Benefits with First- and Second-order Features

Abstract

Conjunction benefits refers to the case in which discriminating the presence of multiple features within an object (feature conjunctions) can be faster than discriminating the presence of the less discriminable feature alone (Fournier et al., 1998, 2000). An asynchronous priming model assumes that conjunction benefits result from early partial decision activation by more discriminable features that are combined with activation by less discriminable features to meet a single decision criterion. Conjunction benefits occur if task-relevant dimensions differ in discriminability and are consistently mapped to a response. However, it is unclear whether they occur when feature conjunctions are comprised of first-order and second-order features. This study investigated whether conjunction benefits occur when first-order and second-order features are combined within the same display. Specifically, observers judged whether one or two features were present or absent in a gabor patch. In one condition, observers made judgments of the (first-order) spatial frequency and (first-order) orientation of the carrier grating. In a second condition, observers made judgments of the (first-order) spatial frequency of the carrier grating and the (second-order) orientation of the envelope. Discriminability difficulty between the task-relevant features was varied in each condition. Results showed that conjunction benefits occurred in both conditions. This suggests that decision activation from second-order features can by primed by first-order features, and vice versa. The implications of these results for feature integration models of vision will be discussed.