Abstract
To anticipate sudden actions in our environment is an important ability based on prior knowledge and experience. Anticipation and prediction allow the visual oculomotor system to reduce inherent sensory processing delays and to produce eye movements to the right location at the right time to optimize sampling of visual information. Most events follow predictable patterns in space and time, but not everything is predictable. Over our lifetime we have learned, what to expect when objects made from different material are exposed to different forces (Alley et al., 2020). But how does visual sampling behavior change if the associations of material properties are violated? We compare eye movements of 14 observers while watching movies which showed eight familiar everyday objects (e.g., chair or teacup) falling from a fixed distance to the ground floor in a virtual room. Upon impact, objects showed either expected or surprising material deformations. For example, a falling chair could tip over but stay solid (expected) or it could splash like milk into little droplets and splatter on the ground (surprising). To test the effect of context cues, and therefore the strength of expectations about an object’s material properties, objects either appeared with the look of their typical optical material properties (rendered) in a natural room or as white high contrast shapes in front of a black background. We found that in the surprise-condition eye movement patterns deviated systematically: after the impact initial fixations were shorter but the next fixations were prolonged and located closer to the object center compared to the fixation pattern of the expected condition. This effect on fixation behavior was stronger for the rendered objects. Therefore, when confronted with unexpected material behavior eye movement strategies are rapidly adapted to maximize information about the material behavior of the object.