  We study the ability of human observer to control fixation duration during
execution of visual search tasks. We conducted the eye-tracking experiments
with natural and synthetic images and found the dependency of fixation duration
on difficulty of the task and the lengths of preceding and succeeding saccades.
In order to explain it, we developed the novel control model of human
eye-movements that incorporates continuous-time decision making, observation
and update of belief state. This model is based on Partially Observable Markov
Decision Process with delay in observation and saccade execution that accounts
for a delay between eye and cortex. We validated the computational model
through comparison of statistical properties of simulated and experimental
eye-movement trajectories.
