Although many aspects of conditioned reflex technique were considered before Pav lov's work, theory of conditioned learn ing was developed largely as result of his studies. This theory (14) attempts to ex plain all modifications of behavior on basis of conditioned reflex. Allport 's ( 1 ) theory of development of social behavior, Watson's (20) behaviorism, and Smith and Guthrie's (16) work are typical of this concept. If conditioned reflex theory of is applicable to all kinds of everyday conditioned reflex technique applied to a less specialized type of should yield valuable data concerning process. A survey of literature concerning applicability of conditioned reflex theory to all modifications of behavior indicates a scarcity of experimental studies which have definitely applied conditioned reflex tech nique to less specialized types of learning. Studies such as those of Jones (11) and of Watson and Rayner (21) do, however, in a general way demonstrate application of conditioned reflex technique in modifying emotional behavior. Thorndike (18), in his investigation of what he calls the principle of belongingness, seems very definitely to have used a phase of conditioned reflex technique. There also seems to be some uncertainty among students of conditioned reflex phe nomena as to whether all of so-called conditioned reflexes are really true reflexes. Tolman (19) limits conditioned reflex learn ing to conditioning of true reflex; i.e., attaching of original unconditioned re sponse to conditioned stimulus. Other aspects of conditioning process, which are less specialized than true conditioned re flex, have been called sign learning by Tol man. Sign learning, according to Tolman, consists of everyday type of in which one learns to respond to a stimulus in a different way from that in which he first responded to it. This interpretation seems to be supported by Cason (5), who says there is considerable doubt whether all condi tioned reactions wThich have been secured were true conditioned reflexes.