Foundations Of Cognitive Science


The Z-lens is an apparatus invented by Eran Zaidel in the lab of Roger Sperry in 1970 (Zaidel, 1975). It is a variation of a contact lens setup used to stablize retinal images (i.e., to present an image to the same receptors on the retina regardless of eye movements). However, in this case what is stablized is a visual half-field. That is, a subject can move their eyes and actively explore a visual stimulus, but only one half of their visual field is stimulated during this exploration. The Z-lens permits visual stimuli to be projected onto the retina of the eye so that they are interpreted either by the left or right hemisphere of the brain, not both at once.

Sperry, a pioneer of the split brain operation, used it the Z-lens demonstrate that split brain patients had two separate visual inner worlds (e.g. Sperry, Zaidel & Zaidel, 1979).


  1. Sperry, R. W., Zaidel, E., & Zaidel, D. (1979). Self recognition and social awareness in the deconnected minor hemisphere. Neuropsychologia, 17(2), 153-166.
  2. Zaidel, E. (1975). Technique for presenting lateralized visual input with prolonged exposure. Vision Research, 15(2), 283-289.

(Revised February 2010)