Again in the second experiment, the subject reacts more strongly to the complex as shown already in explaining the first experiment and for the same reasons. It might be said that in looking at the colored figures, e. g., that since the same amount of retina is stimulated, the reaction ought to be the same. But we may presume that the complex figure, on account of the different shapes and contrasts on its surface, will more variously affect the same amount of retina and that the nervous currents sent to the cortex will, many of them, be stronger than those from the simple figure and will thus cause the cortical cells to be more strongly excited, or by a process of irradiation the stimulation will spread to adjoining cells and thus finally more cells be stimulated. However this may be, the amount of discharge into motor cells is certainly greater and the muscular reaction, therefore, also greater.
The interesting side of our results is thus given in the fact that we have here two activities—counting with highest speed and making hand-movements of certain length—which are performed every time with exactly the same intention and with the subjective impression of equal result, and which yet show marked differences according to the complexity of the psycho-physical stimuli. It is a new contribution to our knowledge of the independent motor power of ideas.
ANIMAL PSYCHOLOGY
THE MUTUAL RELATIONS OF STIMULI IN THE FROG RANA CLAMATA DAUDIN[139]
BY ROBERT M. YERKES