With our brain being the largest sex organ, it's no wonder almost everyone has sexual fantasies at one time or another. In fact, about 85 percent of adult women indulge in erotic thoughts, according to Brett Kahr, a British psychotherapist and author of Who's Been Sleeping In Your Head: The Secret World of Sexual Fantasies.

Sexual fantasies survey findings

Kahr, who conducted a large-scale study of the sexual fantasies of 23,000 adults, reveals that many people fantasize as a way to fulfill often unconscious psychological needs, and a means of exploring sexual activities inaccessible in real life.

Some surprising findings from his study:

• About 90 percent of adults fantasize about someone other than the person they're having sex with
• 41 percent imagine sex with someone else's partner
• 39 percent fantasize about sex with a work colleague
• 25 percent (particularly men and young adults) fantasize about celebrities
• 18 percent of women fantasize about sex with two or more men
• 28 percent of women fantasize about sex with two men, while 58 percent fantasize about sex with two women
• 25 percent fantasize about being tied up
• 18 percent of men and 7 percent of women fantasize about spanking someone
• 11 percent of men and 13 percent of women fantasize about being spanked
• 85 percent have never shared their deepest fantasies, nor acted them out