A guy that is in a relationship was chosen by the girl he is in a relationship with.

This makes him of social value.

He has been socially approved by his girlfriend.

Girls are drawn to guys who are already socially approved.

It is as though these guys have already been vetted by virtue of being in a relationship.

This must mean that he is socially skilled, with a life that is reflective of someone admired and respected.

When a guy is already in a relationship, he has already demonstrated the ability to get a girlfriend.

A guy that is already taken isn’t desperate for her attention.

He already gets attention from his girlfriend.

A girlfriend that deemed him worthy of making her boyfriend.

This must mean that he has desirable qualities.

She becomes curious and takes a closer look at him, studying his physical features, behavior, and lifestyle.

She wants to get a read on what made him so appealing to the girl that chose to make him her boyfriend.

As she investigates, it dawns on her that he has specific physical features and personality traits that she deems attractive.

Soon after, she becomes curious about the girl he is in a relationship with.

She now wants to know what it is about her that made him choose to make her his girlfriend.

Instinctively, she compares her own physical appearance to that of his girlfriend.

There is a curiosity factor around who she believes to be better looking.

Is his girlfriend prettier than her?

Before she knows it, she is examining her facial features in comparison to that of his girlfriend.

She is curious about whether she has nicer eyes, hair, cheeks, jaws, lips, hair, etc., than his girlfriend.

Once she determines who is prettier in the face, she looks to the body.

Does she have a nicer body than his girlfriend?

She examines everything from their shapes to their weight.

By allowing this sort of comparison to develop in her mind, she is unconsciously competing with the girl he is in a relationship with, as she ascertains who is more attractive.

When a guy is already in a relationship, it triggers a hormonal response from women.

A response that is biologically innate.

This is a guy that was picked by another women.

This must mean he has value.

This biological thought process goes back as far as the early humans.

The men who were the most desirable were the ones who had already been picked by other women.

This was why as little as a handful of popular men in the village often bedded multiple women and fathered multiple children with said women.

That hasn’t changed in modern times.

Women respond favorably to a man who has already been picked as a partner by another woman.

It means he already must possess desirable qualities.

Being women, they assume that other women look for similar qualities in a man they choose to date.

When a guy is already in a relationship, it’s as though these women are given a shortcut.

They don’t have to wonder about his desirability as a mate, that has already been determined by the girl who chose to make him her boyfriend.

Furthermore, the fact that he is in a relationship makes him unavailable to her.

Something that isn’t readily available in and of itself possesses value.

This unavailability factor makes him that much more attractive.