Principles of Design: Orientation Sensitivity
A phenomenon of visual processing in which certain line orientations are more quickly and easily processed and discriminated than other line orientations.
The efficiency with which people can perceive ad make judgement about the orientation of lines is influenced by a number of factors. For example, standard analog clocks are easier to read than twenty-four hour clocks because the numbers on standard clocks are separated by 30 degrees, which is detectable. The numbers on twenty-four hour clocks are separated by 15 degrees.
Orientation sensitivity is based on two phenomena that are observed in visual perception: oblique effect and pop-out effect.
Oblique Effect - The ability to more accurately perceive and judge line orientations that are close to vertical and horizontal, than line orientations that are oblique. The effect is caused by a greater sensitivity of neurons to vertical and horizontal stimuli than to oblique stimuli. People tend to make judgments about line orientation that are biased toward the nearest vertical or horizontal axis.
Pop-out Effect - The tendency of certain elements in a display to pop out as figure elements, and as a result be quickly and easily detected. The effect is caused by a change in the visual stimuli sufficient to activate additional input neurons, which then help to detect differences in line orientation and patterns.
Design Tips For Orientation Sensitivity
Designs in which the primary elements are vertical or horizontal are considered more aesthetic than designs in which primary elements are oblique.
Consider orientation sensitivity in composition requiring discrimination between different lines or textures or decisions based on the relative position of elements.
Facilitate discrimination between linear elements by making their orientation differ by more than 30 degrees.
In displays requiring estimates of orientation or angle, provide visual indicators at 30-degree increments to improve accuracy in oblique regions.
Use horizontal and vertical lines as visual anchors to enhance aesthetics and maximize discrimination with oblique elements.