The precise history and nature of the motives that are at work here are not as yet completely understood, and we shall have occasion to consider the subject again at a later stage of our present enquiry. There can be little doubt that one of the factors concerned is to be found in the suggestive influence of social pressure and tradition manifesting itself in the case of the child, through the behaviour and expression of the adult persons with whom it is brought into contact[16]. In appreciating and responding to these influences, the child is probably helped by a special instinctive mechanism which tends to make it conform to the behaviour, opinions and emotional atmosphere of its human environment. A "herd instinct" of this kind is regarded by some psychologists as constituting the moral force operating as one of the opposing tendencies in all intra-psychical conflicts such as that with which we are here concerned[17]. It is indeed almost certainly a factor of very considerable importance in this connection; the manner in which sexual restrictions and inhibitions so markedly vary from one time, place or social condition to another indicates that there is no deep rooted instinctive tendency towards the suppression of any particular manifestations of sexuality, but rather that the nature of the modifications and restraints undergone by sexual activities is determined for the most part by prevalent moral conventions passively taken over by the individual from the society in which he finds himself. Nevertheless, it would seem doubtful whether the practically universal existence of some kind of sexual restriction can be entirely accounted for in this way. For other reasons it would appear probable that a tendency to some sort of quite general inhibition of primitive sexual activities is part of the original mental endowment of each human individual, even though the particular manifestations of this inhibitory tendency are principally determined by suggestive influences from the environment. To this point also we shall have occasion to revert later on, when we shall be in a more favourable position for forming an opinion with regard to it. [Sidenote: Love, gratitude and admiration]