I broke up with my boyfriend because he didn't prioritize our relationship and wouldn't commit. He now wants to get back together and has been sending me cards and letters for weeks. Is it foolish to give him another shot?

--Red Flag?

A man who's all, "Forget the Tinder randos! I need you!" is a man whose sexual freedom means less to him than being with you. It's basically like a lion knocking on the door of the zoo: "Got a cage for me?"

Still, it's natural you're giving his pleas to get back together the side-eye: "Hmmph. So...I wasn't good enough for you before, but I'm suddenly good enough for you now?!" However, his unwillingness to commit may have had little to do with you.

There's this myth that you just need to find "the right person" and then you and Senor Perfecto ride off into the sunset together to Happily Ever After. In fact, clinical psychologist Judith Sills explains that you need to find not just the right person, but the right person at the right time: when both you and he are ready to commit. "Readiness" doesn't strike lightning bolt-style; it develops. It's a psychological shift that acts as a "catalyst for commitment": for the intimacy, vulnerability, and responsibility for another person that commitment entails.

Evolutionary psychologists David Buss and David Schmitt observe that having sex can ultimately cost women vastly more than it costs men: nine months of pregnancy plus a squalling kid to feed versus a teaspoon of sperm plus a wave goodbye. So, for men, "a short-term sexual strategy" -- casual sex with a variety of women -- has "reproductive benefits," allowing them to leave more descendants carrying their genes (in contrast with a "long-term sexual strategy," commitment). However, which strategy is optimal for an individual man or woman is context-dependent. Contexts that motivate a man to commit include wanting a family, a meaningful partnership, and/or a "highly desirable woman" who can afford to put her foot down: "Relationship or bust, Bob."

Chances are the "foot" scenario is behind your previously blase Bob's transformation (probably along with how we don't always realize what we have until we've lost it). Tell him something soon -- either that you'll hear him out or that it's over. If it's the latter, knowing now will allow him to go out with dignity -- before he scrapes bottom on chick flick lines to poach for his letters and decides begging for love can be genderfluid: "I'm also just a girl, standing in front of a boy, asking him to love her."

For pages and pages of "science-help" from me, buy my latest book, "Unf*ckology: A Field Guide to Living with Guts and Confidence." It lays out the PROCESS of transforming to live w/confidence.

I'm a 32-year-old woman with a pattern of getting into relationships and then not wanting to have sex. I'm really into sex when the relationship's new. But about a year in, I stop wanting to have sex, even when the emotional part of the relationship is good. Why does this happen, and is it preventable?

--Dismayed

Over time, everything gets old. Even men and women who are into the freakiest sex eventually look over at their partner all, "Ugh. Not another night of the same old-same old in the sex dungeon."

Where men and women tend to differ is in their motivation for having sex once they're in a relationship. There's an assumption that, in relationships, women's sexual desire will work just like men's -- that is, rise up out of nowhere (like teenage boys' inappropriate erections). Sexual medicine specialist Rosemary Basson, M.D., finds that this "spontaneous hunger" to have sex is a thing for women in the initial dating stage and for some women in relationships, especially if they and their partner are apart for a few weeks.

But many women in long-term romantic partnerships stop having the physical craving to get it on -- the urge for sexual "release." However, they might still be motivated to have sex for other reasons, like to feel close to their partner. Unfortunately, like you, they and their partners often assume their sexual desire is dead and gone. But Basson explains that a woman's desire is probably arousable, meaning triggerable. (It just needs waking up.)

In practical terms, if a woman who wants to want sex starts making out with her partner, she's likely to get turned on. This becomes the springboard to her feeling that physical urge to have sex. However...this assumes she was seriously attracted to him to begin with and didn't just succumb to advice to be "open-minded" about a great guy she found sexually meh. Initially, excitement over what's new (new guy!) is often mistaken for the excitement of finding somebody hot. However, if actual attraction wasn't there at the start, there'll be nothing to revive once the early sexual disbelief -- "How do you even do that? Are you double-jointed? In Cirque du Soleil?" -- erodes into "Cirque du So Tired Of This."

For pages and pages of "science-help" from me, buy my latest book, "Unf*ckology: A Field Guide to Living with Guts and Confidence." It lays out the PROCESS of transforming to live w/confidence.

My boyfriend is very successful, with a high-profile job in finance. He's very romantic, and I felt I'd found "the one." However, he has cheated on previous girlfriends, is unusually protective of his phone around me, and otherwise acts secretively. For example: He began disappearing for three hours on Wednesday nights. He didn't return any texts, which is unlike him. He claimed he was at "therapy," forgetting he'd told me he instead uses life coaches at his job. Another example: I stopped over one morning and saw remains of a pizza and a dainty box of sparkly champagne gummy bears (not exactly a man's snack). After I called him on these incidents, he began texting me periodically on Wednesday nights and stockpiling cheap drugstore gummies, which he eats when I'm over. He has angrily denied he's seeing other women and refuses to discuss it further. I'm in love with him, and I want to believe him.

--Benefit Of The Doubt?

Believing you've found love has a dark side: wanting to keep believing. The most outrageous claims can take on an air of plausibility, like when your friend tells you she spotted your boyfriend licking some woman's tattoo, and he angrily insists he was saving somebody dying of snakebite -- uh, in Midtown Manhattan.

Your brain is partly to blame. Human brains have a collective set of built-in errors in reasoning called "cognitive biases" that prompt otherwise smart people to act like they have the IQ of a root vegetable. Crazy as it is that our brain would evolve to have built-in errors, this is actually not a bug, but a feature: one that sometimes acts like a bug.

Our mind needs to take mental shortcuts whenever it can. If we had to methodically think out our every action (starting with, "How do you turn on the light in the kitchen, and is that even a good idea?"), we'd wake up at 8 a.m. and need a nap by about 8:17. So, we're prone to cut out the wearying middleman -- careful deliberation of all the facts at hand -- and leap to conclusions about what to do or believe. However, we don't do this at random; we default to "heuristics" (aka "rules of thumb") -- broad, general principles that evolved out of human experience -- to make semi-informed, "quick and dirty" guesses.

Though these guesstimates are typically "good enough" solutions in do-or-die situations, they also lead to cognitive biases, those absurd errors in reasoning that can muck up our lives. Two that might be mucking up yours are the "sunk cost fallacy" and "confirmation bias."

The sunk cost fallacy is the irrational tendency to continue investing time, money, or effort in some losing endeavor (like an unhappy relationship) based on the investment we've already "sunk" into it. Of course, that prior investment is gone. The rational approach would be future-oriented thinking: assessing whether we'd get enough out of any further investment to make it worth throwing in more love, money, or time.

Confirmation bias reflects our tendency to favor information that confirms a belief we already have -- like, "I found Mr. Right!" -- and reject information that says (or screams) otherwise: "I found Mr. Juggles Women Like A Moscow Circus Bear."

If you are succumbing to these cognitive biases, they probably have a co-conspirator. Cross-cultural research suggests that female emotions evolved to subconsciously push women to seek high-status "providers," even when women are high-earning bigwigs themselves. In other words, you might be prone to ignore any intel suggesting your wolf of Wall Street spends a good bit of his week raiding the hussy henhouse (aka Tinder).

In short, though we humans (the snobs of the mammalian world!) smugly refer to ourselves as "rational animals," we are able to reason, but we don't always get around to doing it. Psychologist Daniel Kahneman explains that our brain has two information processing systems, our "fast" emotion-driven system and our "slow" rational system. The emotion-driven fast system is behind our mental shortcuts. It rises up automatically, requiring no work on our part. (We just experience emotions; we don't sit around emotionally dead until we put effort into yanking one up.)

Reasoning, on the other hand, takes work: mental exertion to pore over and analyze information in order to make a decision. Tempting as it is to believe you've found "the one," making yourself take the slow approach -- doing the work to see who a man really is -- will, at the very least, help you boot the bad eggs faster. Sadly, we live in an imperfect world -- one in which "pants on fire" is merely a figure of speech, not what happens when your half-undressed boyfriend says (with a totally straight face): "Amber and I were just about to have a work meeting." You: "In our bed?"

For pages and pages of "science-help" from me, buy my latest book, "Unf*ckology: A Field Guide to Living with Guts and Confidence." It lays out the PROCESS of transforming to live w/confidence.

Getting my boyfriend to talk to me about his feelings seems impossible. I know guys tend not to be super emotive, but trying to get a read on what he's feeling is like trying to understand a foreign language. How can I get him to open up to me?

--Distressed

If only the Rosetta stone had included a fourth language: Heterosexual Male.

The Rosetta stone, for those who ditched history class to smoke pot behind the dumpster, was a tabletlike rock fragment that turned out to have the same message in three languages: Egyptian hieroglyphics (long considered undecipherable), another equally mysterious form of Egyptian writing, and ancient Greek. The Greek words were the key, finally allowing scholars to translate hieroglyphics (the ancient Egyptian version of texting somebody a slew of emojis).

Getting back to your own translation issues, it's understandable you're frustrated by the language barrier, or rather, the lack-of-language barrier in your man's continuing adherence to Mute Boyfriend-ese. Shouldn't two adults in a relationship be able to engage in open discussions about their feelings?

Unfortunately, if they're male and female, maybe not. Men and women have some major differences in what I'd call "emotional literacy": the ability to read emotions, both in oneself and others. Men are not the unfeeling louts they're too often made out to be. However, women tend to show more emotion than men and be better at guessing others' feelings. (Compared with most men, they're practically emotional psychics.) Research by psychologist Simon Baron-Cohen suggests that women are the emotional specialists of our species, driven from childhood on to identify others' emotions "and to respond with the appropriate emotion."

Men, in contrast, basically "major" in engineering from childhood on. Baron-Cohen explains that they're driven to decode the workings of machines, math, objects in motion, and other "rule-governed" (and thus relatively predictable) systems. A boy will take a screwdriver to a radio to see how it generates sound; a girl will mentally take apart her cousin to figure out why she's suddenly gone all Bummerella.

These differences come not from "the patriarchy" or Disney princess movies but from millions of years of evolution. Differences in male and female physiology carved out differences in psychology and divisions of labor along male-female lines. Women, whose bodies are baby food dispensaries and who are children's primary caretakers, evolved the emotional makeup to suss out the needs of infants, who lack the spoken-word skills to yell, "Hey, Ma, gimme a beer!"

Men, who evolved to be the warriors of our species, benefit in combat situations from being less in touch with their emotions -- especially fear and sadness -- explains psychologist Joyce Benenson. This would allow a man to storm into battle and get up close and spear-y with the enemy instead of doing what I, as an emotionally aware woman, would probably do: freeze, cry, and wet my pants.

Of course, many individual men and women don't fit neatly into the "men tend to"/"women tend to" boxes. For example, I'm not surprised by a recent archeological finding suggesting ancestral women (and not just men) were hunters. (Of course, a hunter-gatherer lady would've spent much of her life pregnant or breastfeeding, and it's hard to spear a wild boar while clutching a hungry baby drinking his lunch.)

I'm likewise not surprised to encounter men who can lay their feelings out like cold cuts on a platter. As for men who can't, there's this notion that people who have trouble identifying and thus expressing their emotions can improve through study and practice. One tool for this is a poster with cartoon faces showing various emotions, each labeled with the particular emotion. (Google "how you feel today poster.")

Realistically, however, the person best equipped to put names to your boyfriend's feelings is probably you. Consider that men tend to express their emotions through their actions: slamming cupboard doors (mad), sulking (bummed), etc. In keeping with that, ask him not about his feelings but about events -- "What happened when you talked to your boss?" "Did that jerk or that jerk of a mountain lion show up on your hike?" -- and you might notice some feelings slipping out.

Ultimately, though, you should consider whether your being happy with this man is contingent on his expressing himself like a woman. If you stay together, you'll probably need to meet him more than halfway, meaning rely way more on guessing his emotions than his putting them into words. Meanwhile, focusing on how men communicate through action should help you see the beauty in, say, your being startled by clanging metal and yelled profanities some Saturday afternoon. You go out to your garage and discover your boyfriend rotating your tires unasked. It's not exactly how Hugh Grant communicates in chick flicks, but if you understand real-life manspeak, you'll respond perfectly: "You had me at #$&%*! worthless tire jack!"

For pages and pages of "science-help" from me, buy my latest book, "Unf*ckology: A Field Guide to Living with Guts and Confidence." It lays out the PROCESS of transforming to live w/confidence.

My boyfriend and I have been together for two years, and my lease is up in a few months. I was thinking about asking him if he wants to live together. When is the right time to move in with someone, and how do you know whether that's even a good idea?

--Housing Crisis

There are people you can share a home with who do not do a slew of annoying things, and they're those who are continuing their tenure on our planet in an urn.

As a failed romantic (aka human-nature realist), I think there's a right time to move in with another person, such as my boyfriend of 18 years, and it's never. That said, in my financial dream world, I'd be into our buying houses next door to each other. Of course, this sort of thing is less practical for a couple with kids because a substantial part of parenting involves finding your children so annoying in the moment that you take steps to civilize them. And let's be honest, all children are irritating (loud, sticky, and often unbelievably tedious), save for those frozen in mute adorableness in photographs, my favorite kind.

There's often financial pressure to live together, especially in urban elitevilles where a grim little closet pretending to be an apartment rents for the price of a gleaming penthouse in any city in the Midwest. Unfortunately, though sharing an apartment saves big on rent, it can cost a couple their relationship if they end up going at each other like rats in an undersized cage.

As for what makes a relationship work, cohabitational or otherwise, there's this notion that couples who have happy, lasting partnerships love each other more than those who break up. Sorry, romantics! Sure, when a relationship is brand-new, affection and lust make for a big heart-shaped airbag against annoyance and resentment. However, in "The Power of Bad," science journalist John Tierney and social psychologist Roy Baumeister explain that, over time, the sweet, tender things each partner says and does matter far less than how a couple deals with "the negative stuff -- their doubts, their frustrations, their problems."

Their book centers on what researchers call the "negativity bias": how we pay far more attention to negative information, emotions, and experiences than positive and give the negative stuff far more weight. The negativity bias is especially toxic in heterosexual relationships, due to some general sex differences in personality and emotional orientation, summed up by researchers as "female demand/male withdrawal."

"Female demand" is driven by how women tend to be higher in the personality trait of "neuroticism," which involves a tendency to react with negative emotions. People high in neuroticism see the world through mud-covered glasses: They're anxious, moody, easily irritated, and perceive intentional slights in incidents others shrug off as the small frustrations of life. Basically, high neuroticism is the personality trait of picky complainers: "You loaded the dishwasher all wrong!" "You're feeding the baby all wrong!" And then the inevitable, "You're climbing out the window and running down the street screaming all wrong!"

Regarding "male withdrawal" (lest you dudes start feeling all smugly superior), men tend to respond to relationship conflicts by going emotionally comatose, experiencing an emotional systems overload that clinical psychologist Robert Levenson and other researchers call "flooding." In short, men are more likely to get overwhelmed by emotion and simply shut down. Not surprisingly, same-sex couples are less predisposed to plunge into a negativity spiral. Tierney and Baumeister explain, "If it's two men, they're less likely to initiate a complaint; if it's two women, they're less likely to withdraw after being criticized."

That said, simply being human -- in a job, a friendship, or a relationship -- makes us prone to go negative. That's important to understand in light of research by psychologist John Gottman surveying couples who'd just gotten married and looking at which couples were divorced six years later. What mattered were not the positive, loving sentiments couples expressed but how they responded to conflict. Citing this research, Tierney and Baumeister explain: "Being able to hold your tongue rather than say something nasty or spiteful will do much more for your relationship than a good word or deed." (Love is not blind, but love can choose to throw on a blindfold.)

When I got together with my boyfriend, I made a pact with myself to never speak to him like I've forgotten I love him. This has helped me avoid going ugly over the years, but I have to give living apart a good bit of the credit. Psychologist Erich Fromm wrote, "Mature love says: 'I need you because I love you.'" Cohabiting love says: "I need you to take out the trash because I'll get 20-to-life for electrocuting you in the bathtub."

For pages and pages of "science-help" from me, buy my latest book, "Unf*ckology: A Field Guide to Living with Guts and Confidence." It lays out the PROCESS of transforming to live w/confidence.