Chimeric Faces

Vision occurs through the projection of neurons in the retina to the cerebral cortex in the manner depicted in the diagram on the left.  As depicted, objects in the left visual field project to the right hemisphere regardless which eye is stimulated.  Much regarding the differential functioning of the two cortical hemispheres, can be learned by studying people who lack the normal connection between the two hemispheres.  The experiment which follows is adapted from that designed by Levy and Heller.  It is designed to study the lateralization of function between the two hemispheres.  This was done by presenting differing information, within a single image, to the right and left visual fields.  They used pictures of faces in which one half as somehow different than the other.  Specifically, they combined sad and happy facial expressions in different ways.  Such a face might be all happy, it might be all sad, or it might be half happy and half sad. Flashing these chimeric faces for very brief intervals, the subject was asked to judge whether the face was happy or sad.