Testing a theory of brain function by computer methods. III. Detecting cerebral asymmetry in normal adults

Pursuing a plan for overall testing of the timing and sequencing of brain processes, testing techniques are introduced for probing a normal adult's short-term central processes, especially those which are employed in reading a digit span of 6 numbers or less. The tests are administered by means of a personal computer and can provide information on the individual subject's characteristic sequencing and timing of particular central processes. In a subject whose first language is read from left to right, the presented tests reported in this paper reveal an asymmetry in normal adults wherein digits presented in the left visual field are processed more efficiently than those presented in the right visual field. It is suggested that the right hemisphere 'holds the image' while the left hemisphere 'transforms' the spatial image into a temporal sequence for use in speech. The 'right-positioned' or 'later' components must be held at least until a successful spoken response is completed.