Like many adults, you may pride yourself on having a “good gut instinct,” especially when you're being lied to. But when the suspected liar is your partner, rationalizations, excuses and even denial can set in. And this is understandable, since it's hurtful to think that a loved one would betray your trust. Instead of going 'round in mental circles, recalibrate your internal “truth-o-meter” with tips from psychologists and experienced interlocutors from the FBI and CIA to know if your partner is lying. These experts say that some verbal and physical signs often – but not always – indicate that someone is telling a lie.

Before you plunge in, establish an “honesty baseline.” Ask some neutral, innocuous questions, such as, “How is the weather out there?” “How was traffic today?” Listen to your partner's tone of voice, watch his or her body language, and pay attention to whether he or she looks you in the eye. Set your “truth-o-meter” accordingly before seeking the answers you're looking for.

• Speech changes: A lying partner may speak in a different tone – either in a lower or higher pitch. Or, they may speak much faster or slower than usual.
• Sudden and/or repetitive coughing. Tension often rises to the surface in falsifiers in the form of frequent coughing or throat-clearing.
• Evasion: “I don't know” is seldom a satisfactory response. People who are lying tend to resort to this response because they literally don't know how to escape from the jam they find themselves in. Similarly, they may provide very short answers or steadfastly refuse to elaborate.
• Suspicious use of the word “no.” Storytellers often say “no” when they really mean “yes.” As they do so, they often: Avoid eye contact, close their eyes, stretch the word out longer than necessary (as in, “Oh, noooooo”), or say “no” in a childlike or sing-song tone of voice.

• Disconnect between words and movement: People who are more experienced with deceit may have learned how to sound convincing. But their body language can belie their words. For example, they may try to reassure you with calming words, but avoid eye contact. Or, they may say “no” while nodding in the affirmative. All the while, their pupils may be dilated, or they may be blinking frequently.
• Covering the eyes or mouth: A prevaricator may shield his or her eyes or mouth, most often with a hand. Indoors, a person may even close his or her eyes; outdoors, he or she may refuse to remove sunglasses while speaking.
• Hyperactive facial or upper extremity activity: A dishonest person may be able to look you in the eye, but the anxiety of doing so (and talking, too) could trigger a physical reaction, including lip-biting, lip-smacking or pulling on the ears. Such behaviors may be annoying, but watch if they segue to hand-rubbing or hand-wringing; these are huge “deceptive indicators,” former CIA officers say.
• Frivolous grooming: Women may begin playing with their hair or straightening an invisible wrinkle on a dress. Men may fuss with a collar or the knot of their tie (since a lie can be difficult to swallow). And people of both genders may take off their glasses and begin wiping them as if their lives depend on a spotless lens.
  
  In the same vein, deceptive people may “groom” their surroundings by manically shifting around utensils, pulling a smartphone close and then pushing it away, or readjusting the alignment of a plate on place mat.

No one sign is “proof” that your partner is lying to you. There are always extenuating circumstances. That annoying throat-clearing? It could be the symptom of an oncoming cold. And that incessant blinking? Maybe a piece of dust has suddenly descended on your partner's cornea. The point is, look for patterns. If they're adding up, and your gut instinct leads you to suspect the worst, choose a quiet time to model good behavior by dealing with the situation honestly. Share your fears. Ask your partner point-blank if he or she is being truthful with you. Wait for a response – and keep waiting until you feel you have elicited an honest one. It's been said that “the truth hurts.” But as you may know, lies can hurt even more.