Got that niggling feeling your guy is not being entirely honest with you? Like when he tells you he had O.T. last night but his mobile was switched off? When it comes to lying spouses, extra-marital affair is usually the first suspicion that pops to mind, but there are many other reasons why someone fibs: To hide an addiction (e.g. gambling), fear of rejection, or to make themselves appear more successful than they really are.

But apart from the occasional little white lies ("Honey, you don't look fat in that."), being lied to by your partner can feel hurtful, not to mention insulting. We asked body language experts to explain which signals can indicate that he's not telling you the whole truth.

The tell-tale signs

When you lie, you often give away certain signs that can indicate your lack of honesty. Even someone who is practiced at lying can unwittingly give themselves away without even realizing it:

1. He can't look you in the eye

People tend to make eye contact when talking, especially in the Western culture, says behavioral expert Seven Suphi. If he usually feels able to look you in the eye but can't do so on some occasions, he could well be lying to you. "We connect when we look each other in the eye so it's like there's nowhere for the lie to hide if eye contact is maintained," she adds.

"Lack of eye contact indicates that the person is avoiding something," agrees Elizabeth Kuhnke, an Executive Presence Coach and Founder of Kuhnke Communications. "If he doesn’t look at you when he's speaking, he's probably searching for the words that will convince you that he's telling the truth."

2. His voice changes

Listen for any changes in his voice when he speaks: A higher-than-usual pitch can be a good indicator that he's feeling uncomfortable about what he's telling you, says body language expert, Patti Wood, particularly for certain questions or statements. A "different" voice is another big giveaway, adds Kuhnke. "If he's holding something back or telling a lie, his voice will have a different quality to his 'normal' voice."

3. He contradicts himself

If his statements don't tally, you can be almost certain that he's struggling to keep pace with his ever-changing lies. Statements that don't ring true may happen when someone forgets their old lies and contradicts themselves with the truth or another lie, notes Suphi. "If his story is confused and the details don't match up, he's most likely lying," agrees Kuhnke. "It's hard to remember all of the details if you're fabricating them as you go along and under pressure, he's going to forget something or say too much."

4. He changes the subject

If you touch on a subject that will require a lie, he may well try to switch to a different topic to avoid having to be untruthful, suggests Suphi. This is a classic way of moving off a topic that one doesn't want to discuss about. If he weren't lying, he'd be okay staying with the topic until it reaches its natural conclusion.

5. He's ultra-defensive

Liars often display a high level of defensiveness for fear of being caught. "Anger is a good cover," says Wood. "Non-verbal clues of anger can mask nervousness, and can persuade the other person to back down or change the subject." He may also change tack altogether by getting mad at you, says Wood.

"You can ask, "What are you defending?" and see how he responds, Kuhnke suggests. If he's not lying, he should be willing to talk in a calm and rational manner.

6. He fidgets a lot

Excessive fidgeting is a huge tell-tale sign, says Suphi, because he's afraid of being caught. "Fidgeting is a displacement activity that indicates nervous energy," says Kuhnke. "Lip chewing and putting his hand over his mouth are signs that he's holding something back."

Trusting your instincts

These signs alone aren't enough to prove that someone is fibbing, however. To get a clearer picture, think about his "normal" behavior and whether he typically acts like this. For example, people who are anxious or lacking in confidence can demonstrate many of these signs as a normal everyday behaviour, such as a lack of eye contact, a nervous high-pitched voice and excessive fidgeting due to the fact that they're uncomfortable in many situations. However, if the behavior is generally out-of-character, there's a good chance that he's not being honest with you and if it's coupled with a gut feeling that something isn't right, you're probably right to be wary.