the less worth noting. The chests are now opened, and, after having shown the audience that the second chest comes out of the first, the third out of the second, and so on, he can very readily and quickly draw the last smallest chest from a groove under the table and bring it out as though it had come out of the next larger chest. This is opened and the trick is done. So thoroughly convinced is the observer by the correctness of his first three inferences that the last box came out of the one before it, that I venture to say this explanation never occurred to one in ten thousand, and that most of the audience would have been willing to affirm on oath that they saw the last box so emerge. The psychology of the process, then, consists in inducing the spectator to draw the natural logical inference, which in this case will be a wrong one.
The more closely the conditions that lead to correct inferences in ordinary experience are imitated, the more successful will be the illusion; and one great principle of conjuring illusions is to first actually do that which you afterward wish the audience to believe you have done. Thus, when coins are caught in mid-air and thrown into a hat, a few are really thrown in; but the others palmed in the hand holding the hat, and allowed to fall in when the other hand makes the appropriate movements. Some of the rings to be mysteriously linked together are given to the audience for examination and found to contain no opening, the audience at once concluding that the rings which the performer retains are precisely like them. In general, to gain the confidence of the person to be deceived is the first step alike in sleight of hand and in criminal fraud.
As we turn from the objective to the subjective conditions of deception, we enter the true domain of psychology; for the most scientific deceiver is he who employs least external aids, and counts most upon his power of captivating the intellect. Just as we interpret appearances by the forms they most commonly assume, so it is our average normal selves that interpret them. A variation in our sense-organs or our judging powers will lead to illusion. The effects of contrast are an apt illustration. Coming from a dark to a light room, the light seems glaringly bright; a hand immersed in hot water and then in lukewarm water will feel the latter as cold; when accustomed to the silence of the country the bustle of the city seems unusually noisy, and so on. Fatigue produces similar results. Fatigue the eye for red, and it sees white light as green; the last mile of a long walk seems the longest; the last hour of a long wait, the most tedious. So long as we recognize our unusual condition and allow for its effects, we are not deceived; but under the influence of emotion this power is easily lost. The delusions of the insane are often misinterpretations of abnormal sensations under the guidance of a dominant
