First, here is an interesting piece on sexual arousal:
“Sexual arousal may occur as a result of mental and/or physical stimulation. This means the arousal can originate in the brain (psychogenic) or in the body (neurogenic). When a woman sees her partner in the appropriate circumstances her brain will find these visual images sexually stimulating. This causes her brain to send messengers throughout her body to prepare her physically for the possible forthcoming sexual activity. Some messengers go to the heart to increase the heart rate, others go to the pelvic organs to increase the amount of blood engorgement. These visual images may initiate sexual thoughts and communication within the brain resulting in increased mental and physical arousal, as may the awareness of her increasing physical arousal. The mind/body connection should serve to increase the level of sexual arousal, as long as the sexual stimulation continues.”
Now, onto the Monkeys. 
This position is called tail-faced fun because,
no matter what direction you are going in, no matter who you do it with,
you will always have a tail in your face.
