Men lie about their penis size to give themselves an ego boost.
Men lie about what is in their pants
A new study has found that men who are allowed to report on the length of their own manhood declare an average that is "dramatically" larger than the norm.
The study recorded physical measurements taken at home by 224 men in Denmark, including penis size.
The nation's average erect length is 14.88cm (5.9 inches), but the respondents put down an average of 18.02cm (7.1 inches).
The experts removed some ridiculous answers, including some who lied that they were bigger than 34cm (13.4 inches) - thought to be the world's largest.
Men were more honest about their height, weight and fitness.
Study author Jacob Dalgaard Christensen, from the Swedish University of Agricultural Sciences, said: "The deviation is too extreme to have occurred due to measurement error.
"The participants' self-reported size was 21.1 per cent larger than the Danish average. Men, on average, exaggerated the size of their erect penis to portray themselves in a self-serving way."