The second basic routine is called form constancy.
Simple plane and spatial objects (e.g. triangles, circles, spheres, but also ships, cars, houses, animals, …) can be identified on the basis of their characteristics and can be reliably recognized in different forms of representation, views and in different variations. Different forms of representation can be e.g. freehand sketches, ruler-caliper constructions, photos, computer images, 3D animations or real models, but can also differ from each other with respect to brightness or a different background. Views can differ in terms of the angle from where an object is viewed (e.g., top/bottom, side, closer/distant). Different variations of an object may be characterized, for example, by different sizes, colors, and patterns. Similar objects can be recognized at the level of form constancy on the one hand, but can also be drawn and described verbally. The level of form constancy shows clear affinity to the factor of the same name of Frostig’s five-level model of visual perception (Frostig, 1972, 1979).