The oblique effect in the human somatic sensory system.

Blindfolded, sitting subjects were asked to feel whether two bars were parallel or not. In 50% of the presentations the bars were parallel to each other. In all presentations either one or two bars were oriented vertically, horizontally, 45 degrees or 135 degrees. In this situation the best accuracy was found when the bars were vertically and horizontally oriented in space. The experiments were repeated with the subjects tilted laterally by 45 degrees. Now the best accuracy was found when the bars were at an angle of 45 degrees or 135 degrees to the length-axis of the body. This means that the oblique effect in the somatic sensory system is of vestibular origin.