Simplify the following text for a Grade 9 native English-speaking person.
Original: Frequency of masturbation is determined by many factors , e.g. , one 's resistance to sexual tension , hormone levels influencing sexual arousal , sexual habits , peer influences , health and one 's attitude to masturbation formed by culture ; E. Heiby and J. Becker examined the latter .
Simplified: Sexual arousal depends on hormones . Other things that the frequency of masturbation depend on are sexual habits .