Oblique effect

People are very good at detecting whether a picture is hung vertical, but are two- to fourfold worse for a 45-degree oblique contour, even when a comparison is available.

[4] Orientation differences also occur in testing the visual brain with probes for cell connectivity [5] and with imaging techniques.

[6] However, in contrast to the strong behavioral effect, evidence for orientation selectivity bias in primary visual cortex is weak and controversial.

[10] Nevertheless, there is an oblique effect for target configurations that do not directly address these "oriented" neural elements early in the visual path into the brain.

[11] Regardless of where in the brain of the human or animals an oblique effect is found, one would still like to know whether it is an inevitable consequence of the way neural signals are processed, or whether it is a minor error that nature hadn't been bothered to correct, or whether it fulfills a function in making us better in handling our visual environment.

[12] Competing explanations have to contend with questions, not yet finalized, of innateness of horizontal/vertical superiority, of body symmetry in anatomical organization, of methodology of measurement, and particularly, of issues associated with perceptual development in infants and children, and across cultures.