A test of the sensorimotor account of vision and visual perception

Two theories define the relationship between sensory experience and perception of location. The doctrine of specific nerve energies relies on hard-wired, genetically specified relationships between stimulation and perception, modifiable only within limits by adaptation. In a newer sensorimotor account, experience tunes the relationship between stimulation and perception. The perception of pressure phosphenes can differentiate the two theories, because the phosphene appears at a location predicted by physiological optics and in a modality predicted by specific nerve energies. Moving a finger vertically along the outer orbit of the eye while pressing gently on it through the lid during nasally directed gaze results in apparent motion of the phosphene out of phase with the finger, therefore in contradiction to information from motor efference to the finger, tactile sense at the fingertip, eyelid and bulb, joint receptors, and proprioception from muscles driving the finger. A test of the sensorimotor theory giving it every advantage had six observers in darkness moving their fingers along the eye and observing phosphenes for 1 h and 2400 motion cycles; the phosphene always obeyed the doctrine of specific nerve energies, never adapting or changing modality as the sensorimotor theory predicts.