Tina Ivančir

When visually perceiving an object or a scene, the final percept isn’t dependent only on the properties of the distal stimulus (i.e., the real object in the geographical environment) or the proximal stimulus (i.e., excitations of the receptors in our retina that the light, bouncing off the real object, gives rise to). A crucial element in the perception of things is also how the viewer processes and organises the input from the retina, based on the current context and previous experience. Koffka (1935) wrote that this perceptual organisation will be as good as prevailing conditions allow, defining the law of Prägnanz or good Gestalt.

To better understand the meaning behind this ‘goodness’ of perceptual organisation, one can study different phenomena in visual perception and the processes underlying them. We decided to focus specifically on hysteresis and adaptation. Hysteresis is the attractive effect of a previous percept on the current percept and is assumed to help with the stabilisation of the perceptual system. In contrast, adaptation is the repulsive effect of a previous stimulus on the current percept and might be involved in noticing and emphasizing relevant and characteristic changes in the stimuli (Snyder et al., 2015).

The processes behind hysteresis and adaptation are yet to be fully explained and their quantification would be useful for their further investigation. We will attempt to quantify parameters related to both processes for the previously collected data by adapting one of the currently available models (predictive coding models, other Bayesian models, drift-diffusion models etc.). In the second part of the research, we will collect and analyse additional data to investigate how short-term context effects like hysteresis and adaptation interact with longer-term context effects (longer-term priors and reference points), which conditions determine their relative influence and how individuals differ in displaying these effects.