Ellipses on the surface of a picture

Shapes on the surface of a perspective picture may be misperceived. Subjects picked a match for an ellipse depicting the circular top of a cylinder. The top was depicted as tilted forward from 5 degrees to 85 degrees, generating a series of ellipses on the picture surface. The matches were biased towards a circle over a wide range of midrange tilts, which suggests that, influenced by features of perspective, they were seen as in-between the shape on the surface and the shape they depicted.