title: What are the shapes of response time distributions in visual search?
abstract: Many visual search experiments measure response time (RT) as their primary dependent variable. Analyses typically focus on mean (or median) RT. However, given enough data, the RT distribution can be a rich source of information. For this paper, we collected about 500 trials per cell per observer for both target-present and target-absent displays in each of three classic search tasks: feature search, with the target defined by color; conjunction search, with the target defined by both color and orientation; and spatial configuration search for a 2 among distractor 5s. This large data set allows us to characterize the RT distributions in detail. We present the raw RT distributions and fit several psychologically motivated functions (ex-Gaussian, ex-Wald, Gamma, and Weibull) to the data. We analyze and interpret parameter trends from these four functions within the context of theories of visual search.
authors.affiliation: Visual Attention Laboratory, Brigham & Women’s Hospital and Harvard Medical School, 64 Sidney Street, Suite 170, Cambridge, MA 02139, USA.
authors.forename: Evan M
authors.initials: EM
authors.lastname: Palmer
authors.forename: Todd S
authors.initials: TS
authors.lastname: Horowitz
authors.forename: Antonio
authors.initials: A
authors.lastname: Torralba
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Wolfe
mesh_terms: D000293:Adolescent; D000328:Adult; D005133:Eye Movements / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D016011:Normal Distribution; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology*; D012016:Reference Values; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult