A new form of saccadic compression of space

Abstract

Humans make saccadic eye movements to collect visual snapshots of the world, and from the resulting sequence of images we build a unified percept by a process called transsaccadic integration. We have recently suggested that transsaccadic integration works by optimal inference from the brain's imperfect visual and eye position signals and that, as a natural consequence, people show saccadic suppression of displacement: they have trouble perceiving stimulus jumps that happen during saccades. Computer simulations of our model predict that these jumps should appear compressed, so that perceived jumps are a nonlinear function of actual jump size. We tested this prediction experimentally. Eight subjects made saccades towards a target that jumped parallel to the saccade. Using a mouse they then moved the target back to what they felt was its presaccadic position, thereby indicating the perceived jump size. All subjects showed the predicted nonlinear compression in their perception of jumps. We suggest that other forms of distorted space perception may also arise from principles of optimal inference.