The brains of paedophiles are abnormally "tuned" to be attracted to the faces of children, according to a study in Germany.
Some 56 male brains were scanned by scientists, including 24 paedophiles, while they looked at photos of men, women, boys and girls faces.
The same face and sexual processing regions of the brain were stimulated when adults saw photos of men and women and paedophiles looked at images of children.
The findings confirmed previous research showing that human face processing reflects sexual preferences.
However, the study found no reason as to why paedophile brain's preferred children.
It also showed, for the first time, that face processing is tuned to the age that is sexually preferred as well as the gender.
The scientists found the brain network activated through sexual attraction was the same between paedophiles and non paedophiles, but the crucial abnormality is the "tuning" to sexual immaturity.
Dr Jorge Ponseti from Christian-Albrechts University in Kiel, Germany, wrote in the Royal Society journal Biology Letters: