Laws of Attention and Laws of Reaction in General
Shifting occurs also in reflex action. Let two stimuli be acting at once, the one calling for one reflex and the other for the opposed reflex (as flexion and extension of the same limb), and the result is that only one of these reactions will occur at the same time, the other being completely inhibited; but the inhibited reflex gets its turn shortly, provided the two stimuli continue to act, and, in fact, the two reactions may alternate in a way that reminds us of binocular rivalry or ambiguous figures. Three fundamental laws of reaction here come to light.
(1) The law of selection: of two or more inconsistent responses to the same situation (or complex of stimuli), only one is made at the same time.
(2) The law of advantage: one of the alternative responses has an initial advantage over the others, due to such factors as intensity and change in the stimulus, or to habits of reaction.
(3) The law of shifting: the response that has the initial advantage loses its advantage shortly, and an alternative response is made, provided the situation remains the same.
These three laws hold good of reactions at all levels, from reflex action to rational thinking.
The mobility of attention obeys these same laws; only, attention is livelier and freer in its movements than reflex action or than the shifting in rivalry. Attention is more mobile and less bound to rigid rules.