Perception Lab

Why identical shapes can look strikingly different Two curved pieces sit one above the other. The lower one seems larger-sometimes unmistakably so. Yet both pieces are identical. This is the Jastrow illusion: a compact demonstration that perception depends not only on what we see, but also on what surrounds it. Both curved shapes are identical, although the lower one usually appears larger. What Is the Jastrow Illusion? The Jastrow illusion is a geometric size illusion invol

Illusory Contours, Visual Completion and the Constructive Nature of Perception There is no white triangle in the image below-no drawn sides, no change in brightness and no complete object. Yet most people see one almost immediately. The central white triangle has no physical outline. Its edges are constructed by visual perception. Before reading further: what do you see? Look at the figure for a few seconds. Many viewers experience a bright white triangle pointing upwards. I

Why perfectly parallel lines seem to slope Rows of black-and-white tiles are separated by straight horizontal lines. Nothing is bent, tilted or uneven-yet the boundaries appear to rise, fall, converge and diverge. The Café Wall illusion shows how strongly nearby contrast can reshape the geometry we experience. Every mortar line is horizontal and parallel, although the staggered tiles make the boundaries appear tilted. What Is the Café Wall Illusion? The Café Wall illusion is

A Classic Visual Trick That Makes Equal Lines Look Unequal Do not reach for a ruler yet. Look at the two horizontal lines and decide which one appears longer. Which horizontal line looks longer? Make your choice before reading the answer. What did your eyes tell you? Most viewers say that the line with fins spreading outwards looks longer than the line enclosed by inward-pointing arrowheads. It is a convincing impression-but the two horizontal shafts are exactly the same len