Acquisition and decision in visual same-different search of letter displays

Abstract

From 2 to 23 capital As, Bs, and Cs were positioned randomly over visual displays varying in sizefrom5 to 10deg square and in luminance from7 to 250cd/m 2, The task was to decide whether all letters were the same or one was different from the rest. Instructions stressed accuracy, and responses were 97% correct. Three experiments with 50 observers varied amount of practice, number of letters (N), and size and luminance of the display. All experiments produced a linear invariance between mean "same" {Mathematical expression} and mean "different" {Mathematical expression} response times in seconds with N as the parameter: {Mathematical expression} ≅ {Mathematical expression}/2+4. The data are consistent with Krueger's same-different decision theory, and with the separation of acquisition from decision processes. © 1983 Psychonomic Society, Inc.