Eye movements in active visual search: A computable phenomenological model

Abstract

We present a computational model and corresponding computer simulations that mimic phenomenologically the eye movement trajectories observed in a conjunctive visual search task. The element of randomness is captured in the model through a Monte Carlo selection of a particular eye movement based on its probability, which depends on three factors, adjusted to match to the observed saccade amplitude distribution, forward bias in consecutive saccades, and return rates. Memory is assumed to operate through tagging of objects already recognized as nontargets, which, in turn, requires their processing within the attentional area of conspicuity (AC). That AC is adjusted so that computer simulations optimally reproduce the distribution of the number of saccades, the failure rate for capturing the target, and the return rate to previously inspected locations. For their viability, computer simulations critically depend on memory's being long-ranged. In turn, the simulations confirm the formation of circulating or spiraling patterns in the observed eye trajectories. We also relate consistently the average number of saccades per trial to the saccade amplitude distribution by modeling analytically the combined roles of the AC in attention and memory. The full Supplemental Appendix A for this article may be downloaded from http:// app.psychonomic-journals.org/content/supplemental. © 2010 The Psychonomic Society, Inc.