but some inner connection. In other words, when the sense stimulus present is the one that ordinarily arouses the mental fact, it is a case of perception; when the sense stimulus present is one that ordinarily arouses some other mental fact, it is illusion; and when the sense stimulus is nil, it is hallucination.

What is commonly called perception is a mixture of perception, illusion and hallucination. Thus in reading, some of the words which we feel ourselves to see are not seen at all and others are seen as quite different from their actual printed forms. There are misspellings in almost every book, but they pass unnoticed, unseen by the mental eye. The ands, thes, ofs and the like are often not present as sensory stimuli at all, the mind making them up out of whole cloth. So also in listening to spoken language we hear words which the ear does not hear at all. If one says rapidly in the proper context 'What time tis it?' or 'Please pass me ge butter,' the error will often be undetected. The letter t is often pronounced as d in such words as ability, certainty, falsity,' but only experts in phonetics notice the fact. Again and again in rapid speech words are totally omitted without anyone being the wiser.

§ 44. The Control of Connections of Impression

What is called the education of the senses and training in observation might better be called training in acquiring associations with sense stimuli. The difference between the untrained and the trained observer lies not in the action of the sense organs but in the previous experience which interprets their messages. The professional tester of tea has not a different tongue but a different set of experiences, a different stock of associations with various

1 Where the t is far removed from the accented syllable.

stimuli. The man of science sees more in the specimen because he knows more about it. One does not learn to see by perpetual staring, but by connecting each sight with knowledge about the thing seen. To educate the senses means (1) to form habits of systematic rather than hap-hazard examination, (2) to learn to recognize elements in complexes by first getting used to them singly, and (3) to connect each sensory stimulus with a separate identifiable feeling and with knowledge of its properties.

Exercises

1. Read again § 8 and recall the results of the experiment there described.

2. Illustrate individual differences in the capacities to feel things and qualities in response to sensory stimuli.

3. Illustrate individual differences in perception due to differences in previous experience.

4. Illustrate the law of diminishing returns in the case of the perception of movements. Of tastes.

5. Classify the following illusions as (A) those caused by the strength of previous habit and (B) those caused by the temporary set of the mind:

:

"An officer who superintended the exhuming of a coffin rendered necessary through a suspicion of crime, declared that he already experienced the odor of decomposition, though it was afterwards found that the coffin was empty." (Quoted from Carpenter's Mental Physiology by J. Sully in Illusions p. 108.)

"I never feel sure after wiping the blades of my skates, that they are perfectly dry, since they always seem more or less damp to my hand." (Sully.)

"If we are seated in a railway train which is quite stationary and watch through the window a train passing ours on a neighboring track, we feel our own train to be in motion in the opposite direction."

"I remember one night in Boston, whilst waiting for a 'Mount Auburn' car to bring me to Cambridge reading most distinctly that name upon the signboard of a car on which (as I afterward learned) North Avenue was painted." (James.)

1

11

2

12

3

18

4

14

5

15

6

16

7

17

8

18

9

19

10

20

FIG. 76.

6. Hold one hand in hot and the other in cold water for a few seconds; then put them both in the same dish of tepid water. Compare the feelings of the two hands.

Experiment 19. Color Contrast.-Take 5 pieces of the same gray paper. Lay them on sheets of white, black, red, green and blue paper. Cover with very thin tissue paper. Compare the five grays.

Take two pieces of the same green paper. Lay one on a red background, the other on a background of its own color. Cover as before and compare the two greens. Do similarly with red on a green and on a red background.

1A

11 "

2 "

12.

8 "

13"

4"

14"

5 "

15 ú

6 a

16"

7 แ

17 1

8 "

18 u

9 " 19 n 10"

20 t

FIG. 77.

Experiment 20. The Law of Diminishing Returns.—(a) Look at line No. 1 of Fig. 76 then at line No. IA of Fig. 77. Is the latter shorter or longer than No. 1. (Do not measure, judge by the eye alone.) Compare similarly lines 11 and 11A, 2 and 2A, etc., recording each judgment. After the 20 judgments have been recorded measure the lines and compare the frequency of right judgments in the case of lines 1-10 with that in the case of lines

II-20.

(b) On a sheet of paper 10 inches or more wide rule five lines 20, 40, 60, 80 and 100 millimeters long respectively. Place beside it a similar sheet and draw lines as nearly equal to the models

as you can without measuring or superposition. Do the same thing with another sheet, and continue until you have 10 sheets, each with five lines as nearly equal to the original models as you can draw them. Find, by measuring, the error made in each of the fifty lines. Compare the amount of the error for the 20 mm. line with that for the 40 mm. line and so on through the series.

Experiment 21. The Law of Association in Perception.Print in the same style and size each of the following words upon a slip of paper and paste on a card about 31⁄2 by 11⁄2 inches: (1) good, (2) boy, (3) house, (4) pasent, (5) scarf, (6) sdirt, (7) chipon, (8) feather, (9) tackle, (10) tooch drwn, (11) genuine,

(12) meawing, (13) reaeoning, (14) initate, (15) stoie, (16) morning, (17) frequmtly, (18) constant, (19) embrarderg.

Expose each (in the order given above) for one or two fifths of a second to some one unacquainted entirely with the cards or the object of the experiment, and have him write down what he sees in each case. Explain so far as you can the percepts felt. Compare the records of men and women in the case of words 6, 7, 9, 10, 15, and 19.

Experiment 22. Look at Fig. 78. Does it seem to be (1) a folded sheet with the folded edge toward you, or (2) a folded sheet with the folded edge away from you, or (3) a group of lines on a flat surface? Continue looking at it steadily. What happens? Make it seem like (1) (without altering the figure itself at