Research interests

In my work, I am interested in what determines how we perceive the world around us. What I find particularly fascinating is the fact that our visual perception is not simply a product of the light that hits our eyes, but is instead strongly influenced by our prior knowledge and expectations.

For instance, our knowledge that light usually comes from above leads us to perceive flat circles as either convex or concave dimples, depending on whether the 'shadow' is on the top or the bottom of the circle. And we have such a strong expectation that faces are convex rather than concave that we perceive the inside of a hollow mask as convex despite all cues to the contrary. See this video for a striking demonstration.

In other words, perception can be seen as a process of inference, trying to arrive at the most likely explanation for our sensory inputs given our knowledge of the world. For example, we have a strong impression of a white square in the image above right, possibly because our visual system deems a square surface occluding parts of the circular orange and lime slices a likely cause of this image. Note that this is not a conscious, delibarate process, as I may appear to be suggesting here, but rather an automatic property of the way our brain processes information.

Prior knowledge is not always as static as in the examples above; in daily life we often form expectations on the fly, based on associations we have learned. For instance, if we hear the sound of an ice cream van approaching, we have a very clear expectation of what we will see (and possibly taste) once it comes around the corner. When such expectations are valid, they help us process sensory inputs quickly and efficiently. When they are wrong, they can impair and bias our perception, especially when sensory inputs are noisy, such as in a rain storm or heavy fog. Many of us will know how eerily like a monster a bunch of clothes on a chair can look in a dark bedroom.

When our brain relies on (abberant) prior expectations too much, at the expense of real sensory inputs, this will lead to hallucinations, as is the case in for instance psychosis and schizophrenia. At the other end of the spectrum, diminished use of prior knowledge has been implied in autism. Understanding the mechanisms by which the brain integrates prior knowledge and sensory inputs will likely shed light on many aspects of brain function and cognition.

If you'd like to read about these topics more in depth, have a look at this review paper.