Such a motto would not frighten away the modern introspectionists, for they, no less than the behaviorists, could find a congenial home in a stimulus-response laboratory. They would begin by studying sensations, and, advancing to more complex responses, would observe the conscious processes entering into the response. {69} But, however useful the reaction may be as affording a sound basis for psychological study, we must not allow it to blind our eyes to any of the real facts of mental life; and, at first thought, it seems as if _motives, interests_ and _purposes_ did not fit into the stimulus-response program. Many hard-headed psychologists have fought shy of such matters, and some have flatly denied them any place in scientific psychology. But let us see. _S ---> R_ [Illustration: Fig. 20.--The symbol of stimulus-response psychology. _S_ means the stimulus, and _R_ the response. The line between is the connection from stimulus to response.] Suppose we are looking out on a city street during the noon hour. We see numbers of people who--lunch over, nothing to do till one o'clock!--are standing or walking about, looking at anything that chances to catch their eye, waving their hands to friends across the street, whistling to a stray dog that comes past, or congregating about an automobile that has broken down in the crowded thoroughfare. These people are responding to stimuli, obviously enough, and there is no difficulty in fitting their behavior into the stimulus-response scheme. But here comes some one who pays little attention to the sights and sounds of the street, simply keeping his eyes open enough to avoid colliding with any one else. He seems in a hurry, and we say of him, "He must have business on hand; he has to keep an appointment or catch a train". He is not simply responding to the stimuli that come to him, but has some purpose of his own that directs his movements. Here is another who, while not in such a hurry, is not idling by any means, since he peers closely at the faces of the men, neglecting the women, and seems to be looking for some one in particular; or, perhaps, he neglects men and {70} women alike, and looks anxiously at the ground, as if he had lost something. Some inner motive shuts him off from most of the stimuli of the street, while making him extra responsive to certain sorts of stimuli. Purposive Behavior Now it would be a great mistake to rule these purposeful individuals out of our psychology. We wish to understand busy people as well as idlers. What makes a man busy is some inner purpose or motive. He still responds to present stimuli--otherwise he would be in a dream or trance and out of all touch with what was going on about him--but his actions are in part controlled by an inner motive. To complete the foundations of our psychology, then, we need to fit purpose into the general plan of stimulus and response. At first thought, purpose seems a misfit here, since--