In this video, Harry Potter can appear to pass through Dobby the elf, but it’s not magic. The illusion, created by Arthur Shapiro and Gideon Caplovitz from the American University in Washington DC, is an example of the different ways our brain can link separate objects in a scene.
When watching the video above, focus on the spot where Harry and Dobby meet during the collision. What do you see? The two figures should appear to bounce off each other and return their separate ways. Now take a look at the scene again, this time while looking at something just above the video but keeping the characters in your peripheral vision. This time, Harry and Dobby should appear to pass through each other, even though they are actually bouncing.
We experience this phenomenon because our brain processes different features of a scene in parallel. Colour and motion, for example, are analysed separately, even though a moving coloured object would be perceived as a whole. In this case, it shows that features can bind to moving objects in different ways. Shapiro writes:
The apparent transfer of features contradicts what would be expected from theories that propose that perception is guided by intelligent inferences about how objects behave in the world