Sex-related myths are widespread, mostly fuelled by the porn industry or lack of sex education. Bring out the ruler. The myth that the average penis is seven inches long has roots in the fact that many studies ask men to “self-report” their penis size (instead of a researcher actually measuring it). In studies where urologists actually measure stretched penile length, the average size ranges from 4.7 to 5.1 inches when erect (3.6 inches when flaccid). A tad shorter.

Researchers also explored some of the most common “indicators” of penis size. Height was slightly related, meaning that the taller men were, the larger their erect penises tended to be – but only to a small extent. On the other hand, factors like weight, length of index figure and foot size were not consistently predictive.

In a comprehensive global study of sexual behaviour, British researchers tested the hypothesis that most promiscuous behaviour in regions like Africa lead to the highest rates of sexually transmitted diseases. That was not the case, as multiple partners were more commonly reported in industrialised countries where the incidence of STDs was lower. This implies promiscuity may be less important than factors such as poverty and education in the transmission of sexually transmitted diseases.

Another common myth is that sexually transmitted diseases can be spread via the toilet seat.  Almost all kinds of germs that cause sexually transmitted diseases can survive for only a short time on the surface of the seat. For an infection to occur, the germs would have to be transferred from the toilet seat to your urethral or genital tract, or through a cut or sore on the buttocks or thighs, which is possible but highly unlikely. There are no real studies or evidence where people reported that this had actually happened.

And finally, some more good news. Contrary to the popular belief that sex needs to last for hours to be considered good, many couples enjoy satisfying sexual intercourse which lasts between three and 13 minutes, according to Penn State Erie researchers Eric Corty and Jenay Guardiani (2008).