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Apparently saying 'Because men are awful.' doesn't cut it with the scientific community.
A 2016 study by Match.com found that 49 per cent of women had been sent a photo of male genitalia which they hadn't requested.
Men seem pretty honest about it too, given that in the same survey, 47 per cent of men admitted to sending one.
Dr. Justin Lehmiller, a writer on sex and relationships, posits two psychological theories for why men send 'd*ck pics'.
This evolutionary theory is one who way to explain why single straight men in conversation with women often mistake friendliness for flirting.
Error management theory argues that men and women have evolved different cognitive biases in order to help with reproduction.
Men can impregnate multiple women at a time, and therefore are always on the look out for a new sexual partners.
The rationale is it's better to strike out and be rejected often, than ever miss an opportunity to procreate.
'Overperceiving' a woman's interest can lead a man to rationalise sending her a photo of his junk.
Lehmiller stresses that even if this behaviour is adaptive, it does not excuse the sexual harassment at work.
The other theory suggested by Lehman is classic 'Look at my weiner' exhibitionism.
Shocked reactions are the turn on for exhibitionists.
According to Lehmiller the behaviour is linked to poor social skills. some scientists to conclude that the behaviour is a means of provoking social interaction.
Away from this extreme, Lehmiller also believes non-gender specific factors such as online anonymity leads more people to share nude photos.
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