Introduction

In 1865, Claude Bernard, the great French physician scientist regarded as the father of experimental medicine, insisted on what he termed the method of counterproof. This is embodied in the Latin phrase sublata causa, tollitur effectus, meaning “remove the cause, eliminate the effect.” Bernard encouraged his fellow physicians to seek for truth by evaluating contradictory facts that challenged their favorite hypotheses, and emphasized that “the only proof that one phenomenon plays the part of cause in relation to another is by removing the first, to stop the second” (Bernard, 1865/1957, p. 56).

Some of the evidence for the role of oculomotor systems is of the type advocated by Bernard, where, for example, as discussed later, vestibular nerve damage was shown to result both in the elimination of the vestibulo-ocular reflex (VOR) and the simultaneous obliteration of perceptual stability. Mostly, however, research reflects a strategy whereby instead of eliminating a given oculomotor system, a system parameter has been altered and changes in perception are subsequently measured. So long as the method used alters only the oculomotor system and is not also capable of directly changing perception, the method is a powerful one for evaluating causal relationships between perception and oculomotor systems.

Topics covered include:

Direct and mediated spatial properties of oculomotor systems.

Where the self lives and works (the ego-center and the cyclopean eye).

Illusions that result from balancing voluntary against reflexive eye movement control signals.