It is generally agreed that information flow through the cortex is constrained by a hierarchical architecture. Lack of precise data on areal connectivity leads to indeterminacy of existing models. The authors introduce two quantitative parameters (SLN and FLN) that hold the promise of resolving such indeterminacy. In the visual system, using a very incomplete database, provisional hierarchies are in line with the recent proposal of higher functions of area V1 and suggest a hitherto unsuspected central function of the frontal eye field.