Nobody ever wants to have to learn how to know if your spouse is cheating on you. But millions of spouses must ask that question, along with "Is my spouse cheating?" every year. According to studies, between 30 and 60 percent of married people have an affair at some point in their lifetimes, and that number isn’t likely to drop anytime soon: Married people 30 years of age and younger are more likely to have affairs than those who are older than 30 because of how often they travel due to work as well as an experience with multiple sexual partners prior to marriage.

Answering "How to know if your spouse is cheating?" is not nearly as easy or as cut-and-dried as it appears on TV and in the movies. While one spouse rifling through the other’s pants pockets, wallet or pocketbook and finding incriminating evidence such as photos, phone numbers and other correspondence makes for a good soap opera, cheating is rarely that easily discovered in real life.

Spouses who are cheating are almost always obsessed with keeping their secret and are not likely to leave obvious clues and hints lying around. Still, while signs of infidelity are not always obvious, here are some things to watch out for if you are wondering how to know if your spouse is cheating:

—Is my spouse cheating? One sign he or she might be straying is unusually secretive behavior. For instance, does he or she take personal calls in another room? Does he or she always clear the cache on his or her laptop? Has he or she purchased his or her own cell phone or laptop for "personal" use? And does he or she get "jumpy" when you pick up his or her cell phone or use his or her laptop? Communicating by cell phone and on the computer is by far the most popular way for a cheating spouse to stay in touch with a new lover, so keep an eye on these gadgets if you’re wondering how to know if your spouse is cheating.

—Is he or she acting different in other ways? Is he or she spending far more time outside the house than usual? A sudden interest in spending a lot of nights at the gym or a lot of overtime hours at the office may be warning signs that an extramarital affair is taking place.

—Have your spouse’s grooming habits changed? Watching your spouse try out new hairstyles, deodorants, perfumes, colognes or aftershaves may be a sign something is amiss. And is he or she buying new—and racier—underwear or taking more frequent showers?

—Another indicator is if your spouse is expressing unhappiness with the marriage and wishing he or she was single. Often times, a spouse conveys such feelings as a means of explaining and excusing his or her infidelity and trying to escape the marriage before his or her actions are revealed.

Asking "Is my spouse cheating?" and beginning to learn how to know if your spouse is cheating are among the toughest things a person will ever have to do. But if you have these suspicions, it’s essential to follow up on your hunches and, perhaps, hire a professional to conduct a more thorough and in-depth investigation.