Changes in saccade kinematics associated with the value and novelty of a stimulus

The kinematics of elementary movements such as saccadic eye movements are highly regular across repeated movements and across individuals. Historically, saccades have been viewed as following a fixed kinematic pattern with a characteristic peak velocity and duration that varies only with the amplitude of movement. Here we show experimentally in humans that saccade peak velocity and duration can be modulated through presenting stimuli of differing intrinsic value, and that repetition of the same stimulus leads to a decline in saccade speed which we interpret as a decline in the value of that stimulus. Surprisingly, we find that, among saccades of comparable amplitude, faster movement is associated with lower variability- contradicting the idea of a speed-accuracy tradeoff. We consider these results in the context of theoretical models that attempt to account for saccade durations through balancing costs that penalize accuracy with costs that penalize movement duration.