Psychical stimuli are perhaps even more important than physical stimuli. Here also seduction has to be considered, especially during the second period of childhood, in which danger may arise from playmates or school-fellows. This applies equally to children of either sex. Danger may also arise from adults, not only through systematic seduction on the part of grown persons who deliberately debase the mind of youth, but also in other ways. The conversations of adults often lead to sexual acts on the part of children, who understand far more of what is said in their presence than grownups commonly believe. While the child is to all appearance immersed in a book, while a girl is playing with her doll, or a boy with his tin soldiers, the parents or some other adults carry on a conversation in the child's presence under the influence of an utterly false belief that the latter's occupation engrosses his or her entire attention. Yet many children, in such cases, are listening to what is being said with all their ears. Especially foolish, however, are those parents who believe that by the employment of innuendo they are able to conceal from any children who may be present the true inwardness of their conversation. In these matters children are as a rule far sharper than their elders are accustomed to believe. It is hardly necessary for me to point out that opportunities for direct observation are especially dangerous to children. I allude more particularly to the case of children living in the same house with prostitutes; but the danger is hardly less when the children have an opportunity of observing their own parents engaged in sexual acts, or even in the mere preparation for such acts. Forel[77] quotes the report of an experienced physician to the effect that the children of peasants who have watched the copulation of animals often attempt to perform such acts with one another, when bathing, or when any other opportunity offers.