hear a bell with both ears or see a star with both eyes you ordinarily feel but one sound or star. Recall and peform the exepriment familiar to childhood by which the eyes are made to see double.

In binocular vision each retina is separately stimulated, but the result in sensation may be (1) two corresponding sights, or only one sight due (2) to the joint action of the two stimulants or (3) to the failure of one of them to influence sensation, or (4) three sights, one due to joint action and two to the separate actions. Experiment 14 shows a case of (1). Cases of (2) and (3) occur of course in ordinary life (cases of 2 occurring during every moment's vision), but they may be seen most clearly by simple experiments. These experiments involve the power to observe near objects while holding the eyes as one would to look at a distant object, and so may require a little practice.

Experiment 15.-Holding the book upright before the eyes at a distance of about 12 inches, look at the drawings of Fig. 68 as you would to look through it at an object in the distance. That is, fixate for a point in the distance, so that the left eye looks at the left hand pair of circles and the right eye at the right hand pair. If this is done the two figures will appear to move toward each other and occupy the same space. If the eyes are kept as if fixed on a distant object, the single figure resulting from the two drawings can be kept in place for examination. Neglect the two hazy figures seen one on each side of it. What does it appear to be? What new feature not present in either of the two figures appears? Do likewise with Fig. 69. Fill out with appropriate words the blanks in the following statement:- In certain cases when one retina receives one impression and the other another impression, the resulting percept is of........, and possesses the quality of .....

Perform the same experiment with Fig. 70. What is the resulting single percept? Do the bars of the cage hide part of the bird or does it hide part of the cage? Does it seem inside or outside or against the front of the cage?

Experiment 16.-Combine the two halves of Fig. 71 by fixating for a point in the distance as in Experiment 15. What is the resulting picture? Hold it steadily for some moments. What happens?

Do likewise with the two drawings of Fig. 72.
Do likewise with the two drawings of Fig. 73.

What is the chief difference between the resulting percepts in Experiment 15 and those in Experiment 16? What are some other differences? What difference between the pairs of objects of Figs. 68-70 and the pairs of objects of Figs. 71-73 seems to account for the difference in the resulting percepts? Fill out with appropriate words the blanks in the following statement: Two differing retinal impressions will result in a single and constant percept if they are the impressions which would ordinarily be or are ... such impressions. They will

caused by result in caused by

.......

......

if they are impressions which could not be

References

A. James, Briefer Course, II. (9-12), III. (28-40), IV. (4753), V. (60-67), XIII. (228-234), XIX. (310-311), XX. (329-330) XXIV. (375-384).

B. James, Principles, XI. (434-447), XVI. (653-658), XVII. (68-75), XIX. (103-106), XX. (449-474).

PART III

DYNAMIC PSYCHOLOGY

$ 30. Introduction

The previous chapters have described the different varieties of mental states, the service performed by each in the conduct of life, and the physiological facts with which they are connected. Equally important-for practical purposes more so-is knowledge of the mind. in action, knowledge, that is, of the facts and laws which determine what any human being will think and feel and do, how he will learn, why he will misunderstand, when he will be interested, what habits he will form, to what sort of intellect and character he ill attain. The science of the mind in action is called Dynamic Psychology.1

If we ask how the baby comes to feel pleasure at pulling and overturning a toy, why we shut our eyes when an object approaches them, or why we feel the sun to be brighter than the moon, common experience readily answers that we are by nature provided with these and other tendencies to think, feel and act in certain ways,that apart from any training the mind of its own accord or, to use a more technical word, instinctively behaves in certain ways under certain conditions.

For very many of the mind's connections we need no other immediate explanation than that human beings are by nature so organized as to manifest under certain cir

1

By some writers it is called functional psychology.