174 PSYCHOLOGY. 



• 



stinct of • shamming death ' is no shamming of death at all, 

 but rather a paralysis through fear, which saves the insect, 

 crustacean, or other creature from being noticed at oil by his 

 enemy. It is parallelled in the human race by the breath- 

 holding stillness of the boy playing ' I spy,' to whom the 

 seeker is near ; and its obverse side is shown in our invol- 

 untary waving of arms, jumping up and down, and so forth; 

 when we wish to attract someone's attention at a distance. 

 Creatures ' stalking ' their prey and creatures hiding from 

 their pursuers alike show how immobility diminishes con- 

 spicuity. In the woods, if we are quiet, the squirrels and 

 birds will actually touch us. Flies will light on stuffed 

 birds and stationary frogs,* On the other hand, the tre- 

 mendous shock of feeling the thing we are sitting on begin 

 to move, the exaggerated start it gives us to have an insect 

 unexpectedly pass over our skin, or a cat noiselessly come 

 and snuffle about our hand, the excessive reflex effects of 

 tickling, etc., show how exciting the sensation of motion is 

 per se. A kitten cannot helj) pursuing a moving ball. Im- 

 pressions too faint to be cognized at all are immediately 

 felt if they move. A fly sitting is unnoticed, — we feel it the 

 moment it crawls. A shadow may be too faint to be per- 

 ceived. As soon as it moves, however, we see it. Schneider 

 found that a shadow, with distinct outline, and directly fix- 

 ated, could still be perceived when moving, although its 

 objective strength might be but half as great as that of a 

 stationary shadow so faint as just to disappear. With a 

 blurred shadow in indirect vision the difference in favor 

 of motion was much greater — namely, 13.3 : 40.7. If we 

 hold a finger between our closed eyelid and the sunshine 

 we shall not notice its presence. The moment we move it 

 to and fro, however, we discern it. Such visual perception 

 as this reproduces the conditions of sight among the 

 radiates, t 



* Exner tries to show that the structure of the faceted eye of articulates 

 adapts it for perceiving motions ahnost exclusively. 



f Schneider tries to explain why a sensory surface is so much more ex- 

 cited when its impression moves. It has long since been noticed how much 

 more acute is discrimination of successive than of simultaneous differences. 

 But in the case of a moving impression, say on the retina, we have a sum- 



