The days of lipstick on the collar may be passed, though that doesn’t mean you won’t catch a smudge of gloss, a whiff of perfume, or find a random purchase reciept in a touser pocket that leads you to wonder. But chances are – what tips you off to infidelity is a technology trail or a behavioural one, and possibly a little bit of both.
Here’s a list of clues your spouse or partner is straying. It combines the best of the “classic” signs along with those afforded by our digital devices.

1. Change in behaviour
Have the usual routines shifted? Do you notice he’s not playing tennis when he used to – or walking the dog or biking with the kids? Is he staying late at the office, sitting up at night in the kitchen, or ignoring regular commitments he’s always responded to?
There may be an excellent reason other than another person in the picture, but marked changes in routine are among the signs that your partner is sneaking around.

2. Sudden unavailability
Beyond late nights at the office or on his computer, if your spouse is unavailable and no one seems to know where he is, you might want to raise an eyebrow. Sure, he could be planning your big birthday bash, but I wouldn’t count on it. And if you check with his friends and colleagues and note a hint of hesitation as they say he isn’t with them? More reason for your antennae to perk up.

3. Interest in personal appearance
If your couch potato is suddenly working those barbells, and it isn’t in the wake of a doctor’s admonishment, he may be sprucing himself up in order to catch – or keep – someone else’s eye.
Maybe he’s ditched the plaid boxers you made fun of for years, he’s grow a mustache (or shaving one off), or suddenly opting for hair plugs. A new interested party tends to make all of us more aware of how we look, and attentive to self-improvement in the looks and style department.

4. Acting guilty
Is he showing up with the box of chocolates? An unexpected bouquet of flowers? Is your Honey home with gifts that are out of the ordinary, signalling guilt for something?
Guilt manifests itself differently in different people – in their speech, their mannerisms, their sleeping patterns, their behaviours – and most people do feel guilty when they’re cheating on a partner or spouse. If you know his “guilty face” or he’s particularly solicitous and it’s out of character, pay attention. It’s a sign of infidelity.

5. Change in sexual behaviour
Are you doing the deed noticeably less often? Noticeably more often? Does he have a few new tricks, or seem reluctant to engage in the same activities he once enjoyed? Sure, maybe he’s been taking an online course in tantric sex (he’s planning ahead for that birthday surprise, right?), but an unexplained departure from your sexual routine (including protection) may mean enjoying activities elsewhere, or at least, considering it.

6. Seeming secretive
Has your once gregarious guy become cagier about his whereabouts? Is he vague when responding to questions? Are you catching him in lies? Is he adding days to business trips, or going away more often? Does he disappear into another room to take phone calls or send texts? Have you noticed an increase in willingness to do errands?
If he seems secretive, he’s probably got a secret. But as suspicion flares, ignorance certainly isn’t bliss.

7. Picking fights
It’s human nature to want to feel like you’re not the bad guy. If your spouse starts picking fights – so you two are at each other – won’t it be easier for him to justify a relationship with someone else?
There are many reasons we pick fights with loved ones – including anger built up from other domestic issues, depression, fatigue, worry, or stress at work. If you can’t put your finger on other causes, picking fights is another sign that points to your partner’s interests being elsewhere.

8. Emotional distance
Like picking fights, pulling away emotionally may result from a growing closeness with another person. While emotional distance can also signal stress, medical problems, family matters, depression – absent these factors, this sign is usually hard to miss.

9. Online and phone use
Sure, he may be researching for a special project on a tight deadline. But if he’s on the computer every night into the night, and he wasn’t two months ago, are you sure there isn’t an ongoing online affair – at the very least?
Maybe he’s involved virtually, or maybe he’s communicating online with someone he’s seeing in real life. Greater involvement in social media and via the phone may indicate extracurricular activity.

10. Your gut
You know that little voice that tells you something is wrong? Your internal GPS? Your intuition? Your gut?
Whether your spouse is having an emotional affair or a physical one, if your gut tells you there’s something off, it pays to heed this particular warning sign.

So what do you do if you suspect your partner of being unfaithful?
While I’ve positioned these signs from the female viewpoint, that by no means makes them less applicable when the shoe is on the other foot.
Statistics clearly reflect that both women and men engage in adultery – and those activities may include online indiscretions such as sexting, which you may or may not consider "cheating" in the traditional sense.
Be very sure you don’t accuse without proof and have an idea of what you’ll do if the answer you get confirms your suspicions.
Remember that there are many reasons for a spouse to stray, that patterns of unfaithfulness are different from a single instance, and your response to infidelity has tremendous repercussions for both of you – and certainly for any children in the picture.