Eye movement trajectories in active visual search: Contributions of attention, memory, and scene boundaries to pattern formation

We relate the roles of attention, memory, and spatial constraints to pattern formation in eye movement trajectories previously measured in a conjunctive visual search task. Autocorrelations and power spectra of saccade direction cosines confirm a bias to progress forwardly, while turning at the display boundaries, plus a long-range memory component for the search path. Analyses of certain measures of circulation and imbalance in the eye trajectories, and their relations with the display area correspondingly subtended, bear signatures of spiraling or circulating patterns. We interpret their prevalence as mainly due to the interactions between three basic psychoneural mechanisms (conspicuity area, forward bias, long-range memory) and two task-specific geometric- spatial constraints on the eye trajectories (central start and display confinement). Conversely, computer simulations of random walks in which all psychoneural mechanisms are eliminated, while geometric-spatial constraints are maintained, show no prevalence of circulating patterns by those measures. We did find certain peculiarities of some individual participants in their pattern selections, but they appear too casual and incidental to suggest more systematic or complex search strategies in our randomized displays of uninformative stimuli.