THE 



POPULAR SCIENCE 

 MONTHLY. 



THE PSYCHOLOGY OF DECEPTION". 



By JOSEPH JASTEOW, Ph.D., 



PEOFESSOE OF ESPEKLMENTAL AND COIIPAEATIVE PSYCHOLOGY IN THE t^s'IVEESITY OF 

 WISCONSIN. 



THE saying that appearances are deceptive is an inheritance 

 from very ancient times. To Oriental and to Greek philos- 

 ophers the illusory nature of the knowledge furnished by the 

 senses was a frequent and a fertile theme of contemplation and 

 discussion. The same problem stands open to the psychologist of 

 to-day; but, profiting by the specialization of learning and the 

 advance of technical science, he can give it a more comprehensive 

 as well as a more practical answer. The physiological activities 

 underlying sense-perception are now well understood ; the experi- 

 mental method has extended its domain over the field of mental 

 phenomena ; and in every way we have become more expert in 

 addressing our queries to the sphinx, Nature, so as to force a reply. 

 To outline the position of modern psychology with reference to 

 this interesting problem of deception is the object of the present 

 essay. 



In a sensation we recognize a primitive element in the acquisi- 

 tion of knowledge. The deprivation of a sense results in a dwarfed 

 and incomplete mental development. This is due, not to the mere 

 sense-impressions that the organ furnishes, but to the perception 

 and co-ordination of these by inferential processes of the higher 

 faculties. It is not the eye of the eagle, but the brain directing 

 the human eye, that gives intellectual supremacy. Physiology 

 recognizes this distinction as one between lower and higher brain- 

 centers. A man may lose his retina, or may have his optic nerve 

 injured, and so be blind in the ordinary sense of the word. He is 

 prevented from acquiring further knowledge by this avenue ; but, 



TOL. XXXIV. — 10 



