Man has instincts as well as the animals and all his mental activity is due to impulses coming from these instincts. An instinct may be defined as an innate specific tendency of the mind which is common to all members of any one species and which impels the individual to react to certain definite kinds of stimuli with certain definite types of conduct, without having first learned from experience the need of such conduct. For example, there is an instinct of pugnacity which impels us to attack that which injures us or interferes in any way with the attainment of our desires, an instinct of flight which impels us to seek escape from danger, a parental instinct from which come the impulses that lead us to protect and care for our young. But, beside impelling the individual to react to certain definite kinds of stimuli with certain definite types of conduct, an instinct, when stimulated, gives rise in every case to an emotion which is characteristic of it. For example, with the instinct of pugnacity, we have the emotion of anger; with that of flight, the emotion of fear; with the parental instinct, the emotion of love or tender feeling. An instinct, therefore, is regarded as a mechanism made up of three parts: First, an afferent or cognitive part, through which it is stimulated. Second, an affective part through which it gives rise to the emotion which is characteristic of it. Third, an efferent or conative part through which it gives rise to a characteristic type of conduct. McDougall gives a list of about twelve instincts, each with its accompanying emotion. These he regards as primary and the source of all thought and action.