Who feels betrayal more Men or Women?

You promised you would never betray me! but you did!

Why do we feel emotionally betrayed if our partner sleeps with another person, even 

though we all know that sex does not necessarily involve love? There are two kinds

of cheating: physical and emotional. The author of the above question is clearly asking

about sexual cheating, however I will address both because in my opinion neither is 

worse than the other (but then again I'm a man).

Sexual (Physical) Cheating

Sex is a biological function. While for the majority of people it is most satisfying when
emotions like love and affection are involved, emotions are not necessary at all for sex
to happen, or for sex to be physically pleasurable. Anyone who's enjoyed casual sex
or had a one-night stand can agree with this.

Couples, whether they're dating or in a long-term committed relationship, pretty
much always involve their emotions in the bedroom, back seat of a car, bathtub,
even kitchen counter.These romantic relationships thrive not just on sexual intimacy,
but also on the core needs of honesty, trust and respect between partners.
Two poeple can have an amazing sex life, but if they don't trust and respect
each other, they will encounter some  suffering and pain in their relationship.

Cheating is not about the physical act of sex. Cheating is about lies,
deceit, and betrayal. A cheater is not simply defined as someone who is intimate
with a person who is not his/her primary partner. A cheater is someone who
establishes a boundary of sexual/emotional monogamy with one partner,  
then gets intimate with a different person anyway, and lies about it.

A cheater betrays their partner, deceives them, and lies about what they've done.

There's a plethora of non-monogamous couples who walk this Earth,
and successfully maintain their romantic relationships while having sex
with other people who aren't their primary partner.

Emotional (Mental) Cheating

You can also call this emotional transference.

Can you keep what we just did a secret?

Emotional cheating is when one partner

begins to bond emotionally with a third party
in a way that feels, to the other partner, like an
act of betrayal. This is cheating just as much
 as sexual infidelity is cheating - but it's much

less discussed, because everyone seems to
have this idea of cheating being a solely
physical act of betrayal. Emotional cheating could be a girlfriend repeatedly revealing her
personal issues to a guy who's not her boyfriend, while she discusses her personal issues with
her actual boyfriend less and less. It could be a husband spending more quality time with a
co-worker than he spends with his own wife. Emotional cheating is more about the way
it makes the cheated-on partner feel betrayed, than the method of betrayal itself.
Sometimes one partner cheats on the other emotionally, without even realizing they're doing it
-- and that stems from a breakdown of communication and/or trust in the relationship.
Anyone who has experienced the effect of emotional cheating, anyone who's felt betrayed
because their partner was "transferring" their feelings of affection or closeness to another,
will tell you that it's just as hurtful as sexual cheating. Emotional cheating comes
from the same place as sexual cheating: there is a basic lack
of trust and respect for each other between partners. One party feels it can't
be honest with the other, or maybe the feeling is mutual.
The method of cheating is different; the result is the same.

We don't feel emotionally betrayed simply because our partner is physically intimate
with another person. We feel emotionally betrayed because our partner does something
that we feel communicates their lack of respect for and trust in our relationship.

Boundaries are different for every couple, especially
these days.
The concept of betrayal can run
the gamut from a years-long affairs,

to a girl's boyfriend stealing a glance
at another girl's ass.
On a very basic level, cheating is betrayal in any form, and betrayal is a symptom of
a relationship that lacks trust and honest.Many couples will disagree on what
constitutes betrayal -and this itself is problematic, because if you don't understand
your own boundaries in a relationship, you can pretty much guarantee you're going
to hurt your partner, or get hurt, whether you intend to or not.

So which woman would a  modern day man do this for? 
The betrayed woman  as he apologizes!
Or  the other woman, as he is trying to impress her?

I will end on this note:

How you feel about cheating depends a lot on your gender.  
Our nature has evolved to ensure the survival of our species
by two distinct roles: man and woman.  

The man impregnates the woman and protects her while she
comes to term, and provides for her throughout the
nurturing process (many decades, ideally).  

The man expects the child to be his and will
fight any man trying to copulate with 'his' woman.
The woman expects the man to support her in this way

and trusts that she is the only priority in his life
(otherwise, in the wild,

she is a bit screwed).

If either the man or woman break this fundamental
trust, then they have big problems: the male is raising a child
that is potentially not his and the female is facing raising
a child with no support.  If you look at this from the view

of optimizing genetic reproduction: ideally, men would be
the sole mate of as many females as possible and women
would have both the best genetic material from the father
as well as the support of the best protector/provider.  

In both cases, polygamy is probably the best way to
achieve it It is literally impossible to overstate the
importance of honesty, trust, and respect

in any partnership.
Do it, "Just Once" and it can become a good habit!