The word instinct is mainly used to refer to behaviors and their types&sbquo or a behavioral ability and the tendency to so behave&sbquo possessed at birth. It implies irrational or impulsive actions or the tendency to act in such a way. The origin of the English word instinct is the Latin word instinctus that means strong impact from the inside or within. It was a word rooted in the basic thinking from ancient times that the human being essentially acts rationally while other animals act impulsively. Ever since Darwin’s theory of evolution&sbquo however&sbquo it has been considered that the human being too has various impulsive tendencies&sbquo just as other animals. McDougall’s instinct theory was structured by positioning this thinking at the foundation of social psychology. He attempted to explain the daily behaviors of the human being by categorizing instinct into 10 types&sbquo including&sbquo the flight instinct&sbquo adverse reaction&sbquo sexual instinct&sbquo gregarious instinct&sbquo sympathy&sbquo and suggestibility. Freud later took up the impulsive tendencies in particular and analyzed the aggressive instinct in detail from the perspective of the ego and sexual instincts. What has been clarified from these studies is the problem of whether an action is caused by the ego or motivation. In the profession of design&sbquo the theory that the act of designing is also an instinctive behavior of the human being is often seen in definitions of design. I believe this is a serious misunderstanding. The explanation that the invention of tools is an instinctive human behavior is certainly persuasive. Designing&sbquo however&sbquo cannot be said to be an intentional act caused by an innate tendency or impulse to make things. Rather&sbquo design is used as a device to stimulate innate actions or the tendencies towards those actions. Design as stimulation&sbquo for example&sbquo that makes people buy impulsively certainly plays a role in supporting economic activities&sbquo and sometimes the libido is at the base of giving gifts or purchasing. There is a theory that these provide structure to the commercialism of design. I believe the structural relationship between instinct and sensitivity is also a theme in the study of sensitivity in design.