We conducted experiments on the topic of memory-based perception using a wide range of neurocognitive methods including laboratory studies, large-scale online studies, functional magnetic resonance imaging, and brain stimulation studies. Generally, we were able to show that people’s perception of complex visual stimuli (such as scenes, and day-to-day objects) capitalizes on prior knowledge. For example, we show that 1) if participants have a strong memory of what object should be appearing in a scene, then they will be able to see these objects as sharper, even if heavily blurred. 2) When participants have expectations of what might be found beyond the boundaries of a picture, then they will tend to remember this picture with additional information on top of what they previously saw, in line with their expectations. 3) A sharp object in a picture, its positioning and its appearance, can help understanding whether a surrounding blurry background is an indoor or an outdoor scene, thus supporting the construction of a sharper background. 4) When people see objects appearing in a scene in a position coherent to what they expect given a scene’s distance (e.g. a large object in the foreground) they will perform better at recognizing that object. 5) The perception of highly familiar objects, such as other people, is strongly influenced by the knowledge and expectations we have about them. Indeed, the perception of a lifted arm is biased by our knowledge of gravity (a lifted arm should fall down), and by our knowledge of what movements a lifted arm can perform (an arm cannot go all the way behind the back). Crucially, using functional magnetic resonance imaging, we show that visual brain regions contribute to knowledge effects on perception. Further, with brain stimulation, we confirm that the activity of these visual brain regions is causally necessary, thus directly implicated in determining such memory-based effects on perceptual operations.
Our results have been presented to national (the Dutch Society for Brain and Cognition winter conference) and international conferences (Vision Science Society Meeting, US; European Conference for Visual Perception; Concepts, Actions, Objects meeting) and have been partly published in Scientific Journals (e.g. Psychological Science, iScience, Current Biology). Other results are currently in preparation for publication. In addition, we exploited the knowledge generated from this project by establishing a collaboration with a local museum on visual impairment. Here, we arranged for the museum visitors (~20000 people so far), a demonstration on inattentional blindness. In this demonstration, we could directly show to the visitors (by making them participate in a short user-friendly experiment) that in absence of expectations (i.e. of prior knowledge) we may end up missing highly visible objects appearing in front of our eyes. Interestingly, we also let them find out that highly familiar and relevant objects, such as other people, may be missed less often, because our visual system is sensitive to these important stimuli even in absence of attention.
