By: Stephanie Pappas, LiveScience Senior Writer

Published: 10/07/2013 01:10 PM EDT on LiveScience

Has spam promising a larger male member with a pill or a cream ever tempted you to click? Hold off, guys. New research confirms that anxiety about penis size doesn't correlate to what's really in your pants.

In fact, plenty of well-endowed men are ashamed of their penises, while lots of men with smaller penises strut their stuff with confidence, according to a study published online Sept. 30 in the Journal of Sexual Medicine.

The findings are no surprise, said study leader David Veale, a psychiatrist at King's College London.

"It's an emotional feeling," Veale said of penis shame. Like other forms of body dissatisfaction, penis-size anxiety is rarely linked to reality, he told LiveScience.

Measuring up

Men worry far more than women about penis size, according to Veale and his colleagues. One study, published in April in the journal Proceedings of the National Academy of Sciences, found that women preferred larger penises only up to a point (anything bigger than a flaccid length of 2.99 inches (7.59 centimeters) did not additionally impress women), and preferences also varied based on a guy's height. A 2012 study published in the Journal of Sexual Medicine found similarly ambivalent female preferences. In that study, women who experienced frequent vaginal orgasms were much more likely than other women to express an interest in better-endowed guys. For women who didn't prefer vaginal orgasms, penis size was a far less pressing matter.

Nevertheless, men continue to fret over the size of their penises, listing it among their top body concerns along with height and weight, according to a 2008 study in the Journal of Health Psychology. Veale and his colleagues wanted to quantify that anxiety — an important step toward being able to evaluate psychological treatments designed to boost guys' self-image.

To do so, the researchers recruited 173 men online and at King's College London, and asked them to complete a battery of questionnaires on body image, erectile function and concerns about their penises. In addition, 46 of the men agreed to have their penises measured by a urologist in both flaccid and erect states.

Feeling shame

By comparing the men's answers to the questionnaires to their stated concerns about their genitalia, Veale and his colleagues were able to narrow down their scale to 10 questions that were sure to reveal a guy's inner fears about his penis. The questions, available for download on the King's College London website, measure a man's fear of being alone or rejected because of his penis size, his terror that others will laugh at him, and his anxieties about being naked around women and other men.

The most surprising response, Veale said, was men agreeing with the following statement: "Others will be able to see the size or shape of my penis even when I have my trousers on."

"That must be extreme self-consciousness," he said.

Among the men tested, 30 percent reported dissatisfaction with their genitals. About 35 percent of the men were very happy with their penis size, with the rest falling somewhere in between satisfied and dissatisfied. Older guys and gay or bisexual men were more likely to show high penis anxiety, the researchers reported. Gay or bisexual men typically have more body-image problems than straight men do, the researchers wrote, and also have more opportunities to compare body parts.

The penises measured in the study ranged from 2.75 inches to 7 inches (7 to 18 centimeters) long in a flaccid-but-stretched state, and from 3.93 inches to 7.87 inches (10 to 20 cm) when erect. Girth ranged from 2.75 inches to 5.11 inches (7 to 13 cm) when flaccid and from 3.54 inches to 6.69 inches (9 to 17 cm) when erect.

(A recent Journal of Sexual Medicine study found that the average American man's penis measures 5.6 inches, or 14.2 cm, long when erect.)

The bottom line to all these numbers, however, is that they meant not a whit for men's perceptions of their penis size. Big or small didn't matter as much as the fears men carried in their heads. Some of those fears came from harsh experience, Veale said.

"Quite a few of them have been teased about their size either by an ex-partner or in the showers as an adolescent," he said.

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