Hierarchical detection structures in vision

A simple example shows that a hierarchy of visual cells can display different behavior for different stimuli. Stimuli with spatial characteristics similar to the receptive fields of a given level in the hierarchy can display summation behavior revealing the organization of that level; but other stimuli may show the organization of cells at other levels. On the other hand, such behavior may not actually occur in vision because the required nonlinearity between levels is very specific and may not be physiologically realistic.