Your man messed up, and you're waiting for an apology so the two of you can kiss, make up, and move on. 

Well, love ... don't hold your breath. Studies confirm what women have long known—men have trouble spitting out the "S word."

Science says it's definitely a gender thing:

1. He doesn't think he owes you an apology. A pair of studies conducted at the University of Waterloo in Ontario found that it's not so much that men are reluctant to admit wrongdoing. It's just that guys have a "higher threshold" for what situations warrant an apology. In other words, his definition of "bad" or "offensive" behaviors drastically differs from yours.

2. He doesn't view apologies the same way you do. Nope, not even close. Women have a tendency to apologize for everything. Ever catch yourself saying, "I'm so sorry" to someone who's going through a difficult situation that has nothing to do with you? You do this naturally as a way to connect with others and to maintain healthy relationships. But then you wonder why the men you love have difficulty doing the same.

The answer is simple, (and I think I speak for all men when I say) we think it's dumb to apologize for anything that's not our fault.

3. Apologizing makes him feel weak and incompetent. Divorce mediator Sam Margulies, Ph.D. believes that one reason guys are apology-impaired is that admitting wrongdoing pushes them way out of their comfort zone. "Men tend to view apologies as humiliating and a loss of face," he explains. "For a man to acknowledge that he has done something wrong often means he feels diminished in the eyes of those who hear the apology."

That holds true particularly for the women they love and to whom they prefer to perceive them as "heroes." Nevermind that his failure to apologize communicates just the opposite to you—that his pride is more important to him than your feelings, and that if he has to choose who's left feeling badly, he picks you. Ouch! Not so brave, courageous, and admirable behavior, is it?

4. He's carrying emotional baggage about apologizing. Harriet Lerner, Ph.D., author of Marriage Rules, points out that when growing up, some guys feel forced to "man up" and apologize so often to their siblings (or whoever) for minor infractions, that their solution as adults is to never say they're sorry again.

Or, maybe your partner had a bad experience in a past relationship where asking for forgiveness repeatedly led to confrontation instead of an accepted apology.

5. He believes actions speak louder than words. He brings you flowers, does the dishes, or texts you at work just to say, "Hi" and that he's thinking of you. These are signs your man is offering a silent apology. He's trying to make it up to you but may have trouble expressing his feelings verbally.

Regardless of why your man is apology-phobic, the fact is you're hurt and can't help but wonder, "How can my partner love me if he isn't willing to acknowledge that he's wrong and say he's sorry?"

These tips might help bring him around:

1. Clue him in. Don't let yourself fester over something offensive your partner has done. Remember, he might not see the situation as apology-worthy, or the same way you do. So, instead of assuming he can read your mind—or your emotions accurately—tell him exactly what happened, how you feel about it, and that you would really appreciate an apology. Then, hope for the best.

2. Don't demand an apology. Dragging an apology out of someone who isn't willing to cough one up will just lead to more frustration and resentment. What's more, you could end up feeling even more sorry you tried to squeeze an apology out of him. If it's not heartfelt, it's just not worth it.

3. Accept his apology graciously. Don't nag. Don't confront. Don't make him grovel. If you try to use this opportunity to teach him a lesson, you may never hear "I'm sorry" again. Your best response is two simple words: "Apology accepted," followed by a hug. Once your man sees how much you appreciate the gesture, he's more likely to apologize again and again.