Neurons in the early visual system are often considered “edge detectors”. However, we previously showed (Martinez-Conde & Macknik, SFN’01) that single cells in area V1 of the awake monkey respond more strongly to junctions than to edges. Therefore, junction processing may not be a subsequent stage to edge processing, but junctions may instead be a more optimal stimulus than edges for early receptive fields. We have now recorded from 110 neurons in the LGN and area V1, confirming our preliminary conclusions. We have also developed computational models of receptive fields in the retina/LGN and area V1, which make quantifiable and principled predictions of how early neurons of the visual system should respond to junctions versus edges. By measuring the response from these models to visual scenes containing edges and junctions we have discovered that early visual receptive fields (i.e. those from center-surround cells, simple cells, and complex cells) are shaped so as to respond more strongly to junctions than...