Standard Split Brain Experiment
In studies of hemispherical differences in visual recognition, stimuli are often presented with a tachistoscope, which flashes an image in a specific part of the visual field so fast that the subject does not have time to move his or her eyes.
In a standard split-brain experiment, a split-brain patient is seated in front of a screen that hides his or her hands from view. Behind the screen there are a couple of objects which the subject cannot see, in this case a deck of cards and a key. The patient focuses their eyes on the center of the screen, and the word "key" is flashed very briefly in the left field of vision. Information from the left field of vision is received by the nonverbal right hemisphere of the brain, and the person is not able to tell the experimenter what they saw. The patient is then asked to use their left hand to reach behind the screen and pick out the object which corresponds with the word that was flashed. Since the right hemisphere controls movement of the contralateral half of the body, the left hand will be able to correctly identify the object, even though the patient is unaware they even saw a word flashed. Further, as long as the object is in the patient's left hand behind the screen and hidden from view, they cannot relay to the observer what the object is.
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