Sensations of fear, apprehension, shock or surprise all give rise to nervous system responses that have characteristics in common with arousal. Some young boys initially orgasm [i] in response to many of these kind of stimuli. But over time adolescent boys come to associate their arousal with psychological stimuli (erotic turn-ons) that are explicitly sexual. They also become increasingly reliant on specific penile stimulation for orgasm.
The sources of first ejaculation are masturbation (two-thirds), nocturnal emissions (in an eight of the cases), intercourse (one boy in eight) and homosexual contacts (one boy in twenty). ‘Wet dreams’ are most common (71% of men) between 21 and 25 when the highest average frequency is about once in three weeks (0.3 per week). By the age of 50 only a third of men have sex dreams, which do not average more than four or five a year.
For a fifth of men (22%) orgasm is primarily a genital reaction while nearly half of men (45%) have some build-up (body tension). The remaining four variations are similar to the first two but can include additional trembling, fainting, frenzied movements, convulsions, collapse, laughter and talking.
As for other male mammals, men are aroused by smells and secretions. A man takes a pride in his erection and ejaculation. A man may want to ejaculate over a lover’s body or to enjoy a woman urinating over his testicles as she rides him, stimulating his penis with her vagina. Men enjoy sharing details of anatomy, secretions and responses. Men want to display themselves specifically when they are aroused and have an erection. Women do not enjoy the same stimuli nor are they aroused by displaying themselves.
Although men enjoy being touched just about anywhere, they foremost hope that a lover will stimulate their penis (by hand, by mouth and ultimately by offering penetrative sex). Looking at and interacting with their own genitals, as well as those of a lover, is emotionally significant to men. Intercourse completes a man’s arousal cycle thereby providing his sense of emotional well-being. So ejaculating into a vagina has a special emotional significance (not for gay men!). But there is no parallel for women.
A man’s interest in his own penis comes from his frequent or regular state of arousal. His interest in the genitals of the opposite sex comes from his sex drive to penetrate a female. A woman conversely is neither spontaneously aroused not does she actively seek penetrative sex. This explains a woman’s sexual passivity with a lover. She has little interest either in obtaining stimulation of her own genitals or in stimulating a lover’s genitalia.
[i] Originally the pre-adolescent boy erects indiscriminately to … emotional situations, … sexual or non-sexual …. By his late teens the male … rarely responds to anything except a direct physical stimulation of genitalia, or to psychic situations that are specifically sexual. (p165 Kinsey 1948)
Excerpt from Sexuality & Sexual Techniques (ISBN 978-0956-894724)