The Society for Human Sexuality grew out of an American university initiative. If you’re interested in sexuality in general then have a look at this site.
Now about tantra and what is the reasoning?
This quote gives a great hands on experiential approach.
Tantric sex distinguishes between the experiences of orgasm and of ejaculation, which is…a fairly revolutionary idea for westerners, who usually think of the two as one. Tantra defines orgasm as the internal experience of explosive sexual climax, and ejaculation as the external expression of it – the losing of the orgasmic energy, in a way, the releasing or letting go of it into the external environment.
With extended practice, ejaculatory control allows a man to separate orgasm and ejaculation keeping his orgasm inside, and enjoy it in it’s circuit through his body…he will no longer be lead around by his lingham – he will be in charge.
Charles Muir, Tantra The Art of Conscious Loving
