We usually have the impression to see the world around us in clear detail. However, detailed vision is at any point in time limited to only a comparatively small area around the centre of the visual field, the part that corresponds to the fovea on the retina. In order to arrive at a clear impression of our complete surrounding, we scan the environment with quick and jerky, so-called saccadic, eye movements, of which we are usually not aware. These abrupt displacements of our gaze position partition the continuous stream of visual input into discrete periods during which gaze is comparatively stable, called fixations. These gaze dynamics imply that every time we perceive something foveally with high resolution we have previously seen the same thing with much worse resolution further in the visual periphery. There is always a so-called visual preview. Researchers have argued that peripheral visual preview information allows to predict upcoming foveal visual information and that this form of prediction could be understood under the currently influential frameworks of predictive processing, and more specifically, predictive coding. This has, however, not yet been tested empirically. The question addressed in the present project was, thus, whether predictive processing and predictive coding can actually explain trans-saccadic preview effects.
It is important for society to understand how we, as humans, perceive the world. The present project is a particular example for the more general idea that expectations affect perception. Understanding to what extent and how exactly expectations affect perception is of utmost importance for human interaction and mutual understanding. Regarding a more technical understanding of expectations, the present project tested the limits of a currently highly influential theory of brain function, i.e. predictive coding.
