My friend is obsessed with dating models. Of course, because he's dating mostly based on looks, these relationships rarely last. He says that he's trying to move up in the business world and that being seen with a beautiful woman makes a difference in how he's perceived. Wouldn't businesspeople be more impressed if he could keep a relationship going, even if it were with a plainer woman?

--Discerning Dude

The problem with dating largely based on looks is that you tend to end up with the sort of woman who's frequently hospitalized for several days: "I was thinking so hard I dislocated my shoulder."

However, your friend isn't wrong; arm candy appears to be the Prada handbag of male competition. Research by social psychologist Bo Winegard and his colleagues suggests that a man's being accompanied by a modelicious woman functions as a "hard-to-fake" signal of his status, as beautiful women "have the luxury of discriminating among a plethora of suitors."

In the Winegard team's experiments, men paired with attractive women were consistently rated as higher in status than the very same men when they were paired with unattractive women. In one part of the study, some men were assigned an attractive female partner. The men were told that they'd be conducting a survey out on campus with her and that they "were to act as if they and their assigned partner were in a happy relationship."

These men were forced to choose between a group of men and a group of women to survey (and thus flaunt their hot female partner to). Interestingly, almost 70 percent of these guys chose to flaunt to other men. This isn't surprising, considering how, as the researchers note, men are "largely" the ones who determine one another's status (within a group of men). Of course, a man's being seen as high-status by other men is ultimately a path to mo' better babes -- so your friend may basically be getting a twofer by showing off to other dudes.

The reality is, once he's more established, his priority may shift from needing a signal to wanting a partner. At that point, he may come to see the beauty in the sort of woman who has something on her mind -- uh, besides a $200 double-process blond dye job and $600 in hair extensions.

I'm a straight guy in my 30s with pretty strong body odor. I saw your column about how more men are doing body hair trimming. I remember you saying not to remove all the hair, and I don't want women to suspect I'm gay. However, I'm wondering whether shaving my pits would help with my BO.

--Pepe Le Pew

When a woman you meet can't stop thinking about you, ideally her thought isn't, "Could there be a small dead animal making its home in his armpit?"

Underarm stink comes from a specialized sweat gland. Your body has two kinds of sweat glands, eccrine and apocrine. Eccrine glands are the air conditioners of the body, producing sweat that's pretty much just salty water to cool us off. Apocrine glands, on the other hand, are scent glands, found mostly in the armpits and groin and around the nipples. And sorry, this is gross: Any smelliness emanating from the apocrine areas comes not from the sweat itself but from bacteria that move in to lunch on it.

So -- intuitively -- it seems like shaving that pit hair (removing it entirely versus just trimming it) would make a difference, giving the bacteria far less of a, um, dining area. Unfortunately, the studies on this are problematic -- with too-small sample sizes (meaning too few participants to know whether the findings reflect reality or are simply due to chance). One of the studies was done not by independent researchers working out of a university lab but by five researchers employed by a multinational company that sells razors and shaving products. This doesn't necessarily mean their results are skeevy. However, a finding like "Let that armpit hair grow wild and free and wave in the wind like summer grain!" is probably not the stuff career advancement is made of at a company selling hair removal products.

Also, as you suspect, shaved pits on a straight man (one who isn't an Olympic swimmer or a serious body builder) may lead women to suspect he is gay or some body-obsessed narcissist. If you do decide to try pit-shaving, in summer heat, you might forgo tank tops and wear shirts with loose short sleeves. And when you're about to get naked with a woman, see that you pre-allay her fears. Explain that the shaving thing is merely about getting the hideodorousness under control -- not getting into a skin-tight dress, a ginormous platinum wig, and a 14-foot boa in "don't f*ck with me!" fuchsia.

I'm doing some work on my landlady's house. She just CANNOT figure out what color to paint it. Now, when a man paints his house, he goes to Home Depot, grabs a few cans of paint, and starts right in. Simple. Git 'er done. Not so with a woman. She'll agonize endlessly over a bunch of paint chips. She'll finally make a decision, but even then, it's subject to change without notice. So, my question: Has anyone analyzed this phenomenon and found a connection with, you know, a woman's "time of the month"?

--Handydude

Some people are just irritating. It doesn't necessarily have anything to do with their ovaries.

Women's house paint preferences, sadly, have not been a prolific area of scientific study. However, there was a bunch of research suggesting that women's mate preferences shift with their hormone levels during the menstrual cycle -- for example, findings that women went for more masculine faces in the fertile phase of their cycle. But there was a problem. These studies had too-small sample sizes and other methodological shortcomings, which can lead to false positives. When psychologist Benedict Jones and his colleagues ran a big long-term study to check these findings -- using more rigorous methodology -- they found "no compelling evidence that preferences for facial masculinity track changes in women's hormonal status."

However, there do seem to be sex differences in decision-making. These differences emerge before the menstruation years, note neurobiologist Ruud van den Bos and his colleagues (referencing others' research on 7-to-9-year-old children). Their own research finds that men and women show "small but consistent differences in decision-making" that appear related to sex differences in the brain -- in information-processing and emotion regulation. Women appear to be "more sensitive" to potential losses (effects of bad choices) -- which, in turn, might make an individual woman more hesitant to settle on a choice. (No choose, no lose!)

The truth is, there are times when we all have difficulty making a choice. Psychologist Barry Schwartz explains that we (men and women) are driven to protect ourselves from regret -- the pain of blaming ourselves for making the wrong choice. Fear of regret makes choosing especially challenging when we have a bunch of options without meaningful differences -- like eight slightly different shades of off-white house paint: "'Creme Fraiche'? 'Coastal Ivory'? Maybe 'Breezy Linen'?..."

As for your observation about the chop-chop way men choose a paint color, consider that maybe the average dude -- one who isn't an architect, a decorator, or a design connoisseur -- might not be so picky about the color of his house. If you want to help your landlady, get some techie friend of yours to Photoshop each color onto the house so the final result is less abstract. Suggest she invite friends over for cocktails to help her choose. This isn't just a social occasion; it's a regret-minimization tactic -- allowing her to disperse the blame for any grim post-painting epiphanies, such as "Ugh. 'Tuscan Yellow' -- or, as we call it in the States, '3-Day-Old Urine Sample.'"

I'm not a very hairy guy -- except in the armpit area. I've seen articles recently saying men should shave their armpit hair. Really? Do women go for this, or (sorry!) do they maybe think you're gay?

--Fur Pits

Your body hair should not tell a story -- like that Fidel Castro and Osama bin Laden actually aren't dead; they're hiding out in your armpits.

Body hair removal for men has actually gone pretty mainstream. Psychologist Gareth Terry, in a 2016 paper exploring attitudes about male body hair removal, found that gay, straight, and bisexual men and women saw male body hair as masculine and "natural"...to a point -- the point at which they found it "excessive" and thus disgusting. For example, as one bisexual dude, 24, put it: "If you have a rug on your torso or back, then try not to display it in public."

In the armpit hair arena, when psychologist Michael S. Boroughs surveyed 18-to-44-year-old American men, he found that 40 percent did some manscaping. Of these men, 62 percent just "reduced" the hair, and 38 percent removed it. (He didn't separate out sexual preference, but I would guess a good chunk of those balding their pits were gay men.)

Sure, some women might be into the Mr. Gorilla Pits thing. But trimmed hair grows back. Disgust is hard to reverse. So grab an electric beard clipper. Prune the hair down to an inch or half-inch or so (making it look short and neat but not like you went to some armpit coiffure place). As a guideline, there's this: If you're taking a woman to a forested area, it should require a trip by car or at least on foot, not just lifting one of your arms.

My boyfriend of two years read my diary and found out that I had expressed feelings for another guy while we were together. I never acted on them (and I wouldn't have), and I probably shouldn't have told the guy I liked him. But my boyfriend shouldn't have been reading my diary! He broke up with me, saying he wouldn't be able to forgive me. Now he wants to come back. What should I do? I don't feel that I can trust him now.

--Disturbed

Having regular sex with you does not give another person the right to rake through your diary like it's the $1 bin at Goodwill.

Your boyfriend probably equated your approaching this other guy with an attempt to cheat, but it sounds like it was something different -- a sort of preliminary investigation into whether you had any chance with that guy. It turns out that we have a sort of inner auditing department that gets triggered to calculate whether "the one!!!" should maybe be that other one.

Accordingly, research by evolutionary psychologists Joshua Duntley and David Buss and their colleagues suggests that we evolved to cultivate romantic understudies -- backup mates whom we can quickly slot in as partners if our partner, say, dies or ditches us or their "mate value" suddenly takes a dive.

What else might trigger going for -- or at least testing the waters with -- a backup mate? Well, though you didn't have sex with this other guy, it seems instructive to look at why women tend to have affairs. Research by the late psychologist Shirley Glass finds that women view seeking love and emotional intimacy as the most compelling justification for cheating. (Seventy-seven percent of women surveyed saw this as a compelling reason to have an affair, compared with only 43 percent of the men. Men were more likely to see sexual excitement as a compelling justification to stray -- with 75 percent of the men, versus 53 percent of the women, giving that reason.)

As for whether you should take your boyfriend back, the question is: What was missing that led you to try to trade up, and is it still missing? We're prone (per what's called the "sunk cost fallacy") to want to keep putting time and energy into things we've already put time and energy into, but the way to judge whether something's actually worthwhile is to assess how well it's likely to pay off in the future.

If you feel (and act) more certain about your partner, he is less likely to have mate-guarding impulses triggered (like the temptation to snoop). However, if you do get back together with this guy, privacy rules need to be spelled out -- and followed. (Presumably, your daily journal entries start with "Dear Diary," not "To Whom It May Concern.")

My husband and I were visiting friends, and he started walking around their house flossing his teeth. I told him this is not okay, but I couldn't really tell him why. Could you please explain why it's not appropriate to go around flossing so I can tell him and get him to stop?!

--Embarrassed

What's next, margaritas and oral surgery on the deck?

Locking doors didn't get added to bathrooms as some sort of design quirk (like shutters that don't shut on those aluminum siding "Tudor" houses in suburbia). Most of the behaviors we perform in bathrooms aren't all that audience-friendly -- which is surely why we don't see Netflix specials like "Mr. Jones Takes a Poo." Though that activity, like flossing, has health benefits, the rest of us don't need to bear witness. In fact, we're grossed out if we have to -- and we seem to have evolved to feel that way.

Evolutionary psychologist Joshua M. Tybur, who researches disgust, explains that our capacity for getting grossed out seems to help us avoid disease-causing microorganisms, which could put a crimp in our being able to survive and pass on our genes. Disgust basically acts as a psychological "Keep Out!" sign when we encounter things that could infect us, like bodily fluids, spoiled foods, insects, rodents, and dead bodies.

Whether disgust is likely to be triggered is actually the perfect guideline for whether some behavior is a no-go in public. As I put it in my science-based manners book, "Good Manners for Nice People Who Sometimes Say F*ck," "consider how pathogens are spread from person to person. If whatever behavior you're contemplating could cause some bit of something -- a piece of chewed food or some bodily icky -- to go airborne, it's bathroom behavior." Explain this to your husband. Ideally, if he has some news to share with your friends, it isn't something along the lines of "Oh, my bad -- a speck of cilantro from last week's sandwich just hit your light fixture."

I'm a woman who judges potential boyfriends by whether dogs like them. My friends think I'm crazy, but I'm convinced that my dog picks up on who a person really is. Is there any research on whom animals are drawn to?

--Muttperson

Dogs have proved useful for sniffing out drug stashes, dead bodies, and IEDs. How great would it be if you could dispatch your German shepherd Tinker Bell into a bar or party to sniff out the human minefields? "Naw...skip this dude. Serious intimacy issues."

People will swear that their dog is a great judge of character -- focusing on the, oh, two times he growled at someone they despise but conveniently forgetting all the times he snuggled up to their sociopathic ex. The reality is, research does not support dogs (or even chimps) having what they'd need to assess a person's character -- a sophisticated cognitive ability humans have called "theory of mind."

Theory of mind describes being able to guess the mental states of others -- to infer what they're thinking or intending. For example, when you see a man across the street get down on one knee in front of a woman, theory of mind leads you to figure he's about to ask her something -- and it probably isn't, "Could I borrow a pen?"

That said, the ballsy little purse Cujo that growls at some Mr. Skeevy probably isn't doing it out of the blue. Dogs do seem able to read even subtle aspects of human body language -- like our tensing up upon approaching somebody we dread talking to -- and they may respond in kind.

However, dogs' perception of people and the world is dominated by their exceptionally powerful sense of smell -- estimated to be between 10,000 and 100,000 times more powerful than ours, according to anthrozoologist and "Dog Sense" author John W.S. Bradshaw.

In other words, though dogs can't read a person's mind, they may be able to smell what's on it -- or rather, the chemical messengers released by what's on it. For example, doggy cognition researcher Alexandra Horowitz explains in "Inside of a Dog" that adrenaline (triggered when a person's afraid or angry) "is unscented to us, but not to the sensitive sniffer of the dog."

Additionally, Bradshaw points out that the types of people dogs are socialized with -- women, men, men with beards, people wearing different kinds of clothes -- make a difference in whom dogs snuggle up to and whom they snarl at.

So, no, your dog is not a leg-humping background-checker. But he can help you see something important about men -- if you look at how a potential boyfriend treats him: with patience or annoyance. And as I often advise, it's also important to put some time (and a lot of observation) between thinking a guy is really awesome and seeing whether he actually is. It's tempting to believe you've found everlasting love, just as it's tempting to believe that your dog is some sort of crystal ball for reading character -- and not responding to how some guy just kneaded all the stuff together for homemade liverwurst and then wiped his hands on his pants.

My boyfriend thinks there's something wrong with me because of how much I sleep. I've always needed to sleep a lot (like, nine hours). I've been tested for everything, and I'm fine. Do some people just need more sleep? How do I get him off my back?

--Duvet-Covered

Okay, so you're the love child of Rip Van Winkle and a log.

Studies on identical twins suggest that our "sleep duration" (how long we tend to sleep) is between 31 and 55 percent "heritable" -- which is to say factory-installed, driven by our genes.

Beyond your boyfriend not being tuned in to the genetics, there's a little-known feature of our immune system -- basically the psychological version of that plexiglass partition in liquor stores in bad neighborhoods -- that may be causing him to worry about your sleepathons. In addition to warrior cells being sent out by our immune system to attack bodily invaders, such as viruses, psychologist Mark Schaller's research suggests we have a psychological warning system -- the "behavioral immune system" -- to help us avoid being exposed to disease in the first place.

This warning system gets triggered by, among other things, atypical behavior -- for example, sleeping far more than most people. To get your boyfriend off your case, you might tell him that being adequately rested is actually associated with lower risk of heart disease, obesity, and psychiatric problems. In fact, it's even associated with less risk of early mortality -- despite the things your boyfriend probably yells in bed: "Hey! Hey! You still alive? Should I call 911?"