My daughter hates it when I cry and unfortunately for her, I cry easily. I cry at movies, weddings, and graduations. I cry watching the Academy Awards, I cry every time I hear “Hey Jude” or anything by John Denver, and I flat-out sob at Sarah McLachlan’s ASPCA ad with the pictures of neglected and abused animals. I don’t mean to give the impression that my crying jags last longer than one or two tissues, and I wouldn’t characterize myself as a full-blown basket case on the sensitivity spectrum, but I’m definitely left of center.

My daughter, on the other hand, is more self-conscious, more reserved, more British, if you will. She stoically wiped a single tear at the end of “Old Yeller,” and the corners of her mouth will quiver when she gets yelled at (don’t judge), but generally speaking, the act of crying embarrasses her. Compiled statistically, my daughter’s and my crying probably averages out to that of a normal person, but I often wonder, if I were less of a cry baby, would she be more of one?

Humans are sympathetic by nature. As social creatures, our survival depends upon our ability to evaluate and react to each other’s emotions. We smile when we are smiled at, we avoid those who appear hostile, we assimilate body language, and we are triggered when we see a person in distress. We are evolutionarily hard-wired to detect an array of feelings through verbal and non-verbal cues. Research shows babies will react to sad voices at three months old and can distinguish facial expressions conveying fear, anger, and happiness at five months. Networks in the brain designed to observe and interpret this information are in place shortly after birth. What we do with the information gleaned from this careful observation lays the foundation for all human connection.

It’s not hard to imagine that for our ancestors to accomplish anything, like procure food or build shelters, they needed to collaborate, and to collaborate, they needed to get along. The ability to influence each other’s emotional state evolved from a mutually beneficial process. If a cave-mother was more productive, cautious, and clever when she’s wasn’t bawling her eyes out, then, dammit, her family was going to do everything in their power to cheer her up. When one mood goes down, another must go up to compensate. Applying this zero-balance theory (or the teeter-totter rule, as I like to call it) to modern relationships, we can see how the adage opposites attract might actually make sense.

Humans cry for a multitude of reasons, and the reasons change as we develop. When we’re young and the pre-frontal cortex part of the brain is in charge, we cry from pain, hunger, fear, fatigue, and frustration. We cry for attention, to make our caregiver aware we need something. We gradually associate the act of crying with the gratifying relief from discomfort. For babies, crying is the only biological defense mechanism in an otherwise helpless introduction to the world.

As we get older, the cognitive area of the brain takes over and dictates behavior via reasoning, and we recognize that physical pain is self-limiting, finite, and predictable. We also learn to differentiate corporeal pain from psychological and emotional distress, or what scientists call social pain. We can turn off or ignore the pathway signals in our pre-frontal cortex in certain situations, like watching our mom leave the room, discovering there are no more Oreos in the package, or getting an injection at the doctor. In essence, we reinterpret what we consider painful. Helpful, yes, in that we don’t burst into tears over incidental bumps, but what about the Sarah McLachlan ads or, heck, have you seen the montage where the dad films his daughter as she grows from 0 months to 14 years? (Do yourself a favor and watch it.)

The tendency in many of us to cry over the smallest heart-tug is a normal reaction to being deliberately manipulated. That’s right, we’re being manipulated. Marketing agents are masters of creating tear-provoking content because it sells their products. However it’s not always sales-motivated: screenwriters, authors, and songwriters all use emotionally loaded devices to attract an audience to view their art. If they can elicit a good cry, the experience feels meaningful.

It is possible that time will soften my daughter’s Kevlar exterior and she will relax into a public crier, but if it means me becoming stony-faced to offset it, I wouldn’t count on it.