Perceiving the size of trees: Form as information about scale.

Physical constraints on growth produce continuous variations in the shape of biological objects that correspond to their sizes. The author investigated whether 2 such properties of tree form could be visually discriminated and used to evaluate the height of trees. Observers judged simulated tree silhouettes of constant image size. Trees were placed appropriately within a ground texture gradient, as were 6 cylinders. Observers judged trees, then cylinders