Ambivalence in modelling oblique saccades.

Human oblique saccades might be made by synchronized but independent vertical and horizontal pulse generators; we call this the Cartesian theory. Another hypothesis is that the oblique amplitude and angle are coded centrally and trigonometrically-derived signals are sent to the horizontal and vertical muscles (the polar coordinate theory). We took a Cartesian model and cross-coupled the two generators to produce saccades identical to those of a polar coordinate model. This is disproof by counter-example: the experimental evidence claimed to support the polar coordinate model does not necessarily do so. Moreover, the behavior reported for oblique saccades is so variable, contradictory, idiosyncratic, and species-dependent that any model of the central organization of oblique saccades is probably premature.