Erection! Duh. Thankfully, it is easy for females to find out if their man is turned on. They simply have to look for or feel an erection. Sometimes your guy might be turned on in his mind, but there might be no physical signs. When these things are not in synchronization, it is called sexual concordance. Women do not experience this as much as men. For women, sometimes the body is aroused but the brain is not, and vice versa. If the sexual concordance is low for your guy, the only way to know his desires is to ask him directly.