Abstract

The choice of where to look next is guided by current perceptual information as well as internal factors such as motivation, current goals, prior experience, etc. I will discuss the development and testing of a mechanistic framework that describes how perceptual and motor-planning processes dynamically interact and give rise to saccadic choices. In traditional studies of choice behavior, a decision based on sensory information is made first and is then followed by a motor report. Choices conceived in such a serial fashion progress slowly (hundreds of ms)—- but under natural viewing conditions the median time between gaze fixations is short (200—250 ms), and the next saccade is always being planned. Our approach is to manipulate time pressure to reveal how perception and attention guide saccadic choices under more temporally realistic conditions, i.e., when the perceptual evaluation occurs rapidly (< 50 ms) and informs oculomotor plans that are already ongoing. By combining behavioral, neurophysiological, and theoretical work, we have developed a modeling framework that (1) is applicable to a wide range of urgent-choice tasks, (2) replicates rich psychophysical data in great detail, and (3) is firmly consistent with activity recorded in the frontal eye field (FEF). In this framework, perception influences ongoing target selection by halting, accelerating, or decelerating developing motor activity. These three forms of dynamical interaction explain in quantitative detail the rapid temporal variations in psychometric performance observed in our urgent tasks; for example, how exogenous (saliency-driven) and endogenous (rule-driven) influences compete when the goal is to look away from a salient stimulus.