SUZI GODSON

Toughie. I guess a guy with a smaller penis finds it easier to pee in, rather than on, the toilet, but the long schlong is more versatile for genital origami. Seriously though, when it comes to sex, an enormous penis is an asset only if you are planning a career in porn. Women, like men, come in all shapes and sizes and our genitals tend to be proportionate.

Put it this way. If 6ft Uma Thurman can park a Volvo XC90, 5ft Kylie Minogue is probably good with a Mini. That's not to say she couldn't cope with a Volvo (the vagina is a Nissan Micra that can expand into a Renault Espace), but the point is, she would be just as happy with a Mini.

When the vagina is in its resting state, the walls connect with each other and it closes around whatever is inserted, regardless of size. It can hold snug around a tampon or it can stretch like elastic to deliver a baby. This ability to adapt to fit any size of penis led the researchers William Masters and Virginia E. Johnson to conclude that penis size cannot have a true physiological effect on female sexual satisfaction. They observed an exhausting 10,000 complete cycles of sexual response to arrive at their conclusions in 1966, but not everyone agrees with them.

My boyfriend wants doggy style sex in front of a mirror

My boyfriend likes to have sex doggy-style in front of the mirror. Both the position and the mirror make me very uncomfortable. Should I tell him?

Background

• My boyfriend wants doggy style sex in front of a mirror

• I'm turned on by my wife breastfeeding

• I eye up women when my wife isn't around

• Should my boyfriend be screened for sexual health?

• Is my friend a nymphomaniac?

In a small study in 2000, Russell Eisenman of the University of Texas-Pan American, found that 45 out of 50 women questioned stated that girth was significant in sexual satisfaction.

Unfortunately, the Eisenman study did not offer measurements as to what an “unacceptable” girth might be. Another survey, by David A. Frederick in 2006, suggests that the average (5.5in long, 4.85in circumference) penis is sufficient for most women. His online analysis of 54,865 respondants found that 85 per cent of women were satisfied with their partner's penis size, yet only 55 per cent of the men questioned felt happy about their genitals.

In a 1988 study published in the Journal of Sex Research, Paul Jamison and Paul Gebhard analysed data from the Kinsey Institute on erect and flaccid penises. They concluded that men's penises fall into two categories: “growers” (those that gain size when erect); and “showers” (those that get erect, but with little change in size).

It is pointlessly masochistic, but there is something reassuring about the tyranny of penis size. Women worry about their weight every 15 minutes, but extreme thinness rarely equates to attractiveness for men. Similarly, the XL penis that so many men aspire to contributes zero to female sexual pleasure as three quarters of all women cannot achieve orgasm through penetration alone. Clitoral and vulval stimulation is the key to female sexual response.

Statistics from the Social Organisation of Sexuality survey (Laumann, Gagnon, Michael and Michaels) reveal that while 75 per cent of men always have an orgasm during intercourse, only 28.6 per cent of women do. This suggests that men need to spend less time worrying about the size of their engine and more time searching for the ignition.

Suzi Godson is the author of The Sex Book (Cassell, £16.99) and The Body Bible (Penguin, £16.99)

DR THOMAS STUTTAFORD

Unlike vegetables such as courgettes, cucumbers or pumpkins grown to win a rosette at a local agricultural show or to satisfy the supermarket buyer, size, colour or shape are not the criteria by which men are judged as lovers. Enthusiastic gardeners compete over the size of vegetables but ignore consistency and flavour and, therefore, the pleasure they could provide. Penises are different. They are created in all shapes, sizes and colours, but fortunately, quality of lovemaking is not determined by anatomical factors.

A large penis, although it may prompt immediate admiration and have a pronounced wow effect, won't make much difference to a man's ability as a lover. Sexual skill depends more on what is between the ears than the legs. The only dubious advantage of a monster penis is that it could lead to a career as a porn actor.

I have discussed penile size and appearance, especially as it varies between circumcised or uncircumcised, with the prostitutes I used to treat in the clinic. The opinion of an average woman, who has relatively few contacts, is too influenced by the intensity of her emotional attachment to men she has known sexually.

The prostitutes, who have no lasting interest in a man, give an unemotional appraisal and this judgment was shared almost universally. For a single night, the prostitutes found that an average-sized penis was easiest to service. They dreaded having to face the potential porn star's huge organ. One group of prostitutes even drew lots when a regular customer with a giant penis came into their street. It was the loser, not the winner, who catered for him.

A very small penis could present difficulties but, at worst, the woman might be bored. There was almost complete agreement among the prostitutes, based on experience rather than affection or emotion, that girth was more important than length. There was complete agreement that, so far as use rather than appearance is concerned, average is best.

As there are variations in size and shape of penises depending on regional, racial and familial inheritance, there is no universal average length or girth. Even so, text books suggest that an average erect penis is between 5in and 7½in, when it is measured from the pubic bone to its tip and between 1in and 2in in girth. Girth and length when non- erect varies according to temperature, but is usually about half of what it is when erect.

There is no minimum size of penis that precludes satisfactory lovemaking. Research published in the Journal of Urology demonstrated that having a micro penis didn't alter a man's chance of finding girlfriends. Furthermore, affairs with men with tiny penises not only lasted as long as those of men with larger penises, but the chances of any long-term relationship or marriage lasting was greater than that of their better endowed contemporaries.

In many ancient cultures penises were venerated as the source of life. The male obsession with size remains, even though it has no cultural or religious foundation. It is now only a manifestation of men being more interested in physical appearance - including their own - than the emotional aspects of relationships.

Dr Thomas Stuttaford, the Times doctor, spent many years working in a genitourinary clinic

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