some of them are guided by the head with no brain more than the head with one...

It will totally depend on the guy.  I was 100% committed to my wife, and she cheated on me.  Where there temptations?  Sure.  But I valued my marriage over everything else.

So please don't lump all men into the "all men are dogs" group.  We get betrayed, too.

I truly think that some men are just fighting for attention and if they can't get it at home they will go elsewhere.  I think some men are destined to not be faithful to one woman for the rest of their lives, because it's in their personality trait to cheat.  My ex cheated on me and he is a very selfish and self centered person, and seeks attention.  He's a very immature person to and I think these characteristics are in some men that cheat.  There are different studies about it out there all over the internet, but I believe that people make their own choices and they know right from wrong, but sometimes they choose the wrong choice and don't think about who it's going to hurt in the long run.  I also read that men (and women) who cheat have communication problems, like when the marriage gets tough, they start running and they run into someone else's arms.  But you know what they aren't solving anything by doing that, what they do is create more problems down the line, because the next relationship they are in, when things get tough in that, guess what--they will do the same thing over and over again like a vicious cycle!!  Or you could say that some men that cheat only think with their private parts and not their brain!!  At least that's what I say about my ex!!  I look at my divorce as a blessing in disguise because I have my life back and can hook up with friends that I had pushed to the side just for him.  I'm sure there are hundreds of theories out there on why men cheat, plain and simple men are like dogs!!