Scientists have long debated what exactly makes us who we are. Are our qualities more influenced by our social environment, or are we naturally inclined to be a certain way? Or -- to complicate things even further -- does our environment affect the way these natural tendencies display themselves?
Well, when it comes to the reasons why we do the things we do, the most complicated answer is usually the correct one.
In recent decades, the government has spent billions of dollars on gene research with the goal of trying to explain how the genes we were born with express themselves in our everyday lives.
Psychologists are optimistic -- though cautiously -- these advancements in gene research will help us understand ourselves better.
We haven't even scratched the surface of the full potential of genetic research, but what we have seen so far looks promising.
One human quality that genetics has attempted to help explain is sensitivity. People who are highly sensitive tend to respond more emotionally to their environments.
They are more inclined to cry during sad movies, jump to use social media to share something that moved them and feel heightened levels of sympathy for poor people and their friends who just got dumped.
Most notably, they are also more inclined to have a negative attention bias, which means they focus more on the negative things in their environment than the positive things.
This bias causes sensitive people great anxiety, especially if the environment they're responding to is new.
Where do these traits come from? Why are some people more likely than others to respond more powerfully to their environment? In other words, why are some people so damn sensitive?
If this sounds like you, fear not: It turns out the answers to those questions do, indeed, have something to do with the way you were born.
Researchers from the University of California, Monmouth University and the Albert Einstein College of Medicine found that being sensitive is an innate trait that's identifiable by physiological reactions, patterns of brain behavior and genes.
In their study, 18 participants viewed photos of either frowning or smiling faces. The researchers then scanned the participants' brain activity while they looked at the photos to assess how emotional their responses were.
They found that people, who were considered to have sensory processing sensitivity (SPS) had greater blood flow to areas of the brain involved with emotion, awareness and empathy -- indicating physical evidence of the presence of the sensitivity trait. This occurred regardless of whether they were looking at the sad or happy photo.
Another 2012 study examined biological proof of sensitivity even further. In the study, researchers Rachael Grazioplene, Colin DeYoung, Fred Rogosch and Dante Cicchetti studied the cholinergic system, a system in our bodies that determines how we respond to new environments and how sensitive we are to stimuli.
The cholinergic system becomes activated when we experience "expected uncertainty," which happens when we're placed in situations where we predict we will learn something new.
For example, when you were a freshman in college, you probably knew you'd be confronted with new experiences.
You experienced those feelings of "expected uncertainty" -- of not knowing who your friends would be, what you wanted to major in, what clubs you wanted to join, how you would handle living away from home and so on.
Some of your peers might have perceived those new experiences as anxiety-inducing, meaning they would have proceeded with caution. Others might have seen them as intriguing, causing them to have been more inclined to explore.
The way both of these groups of people responded to those new environments was influenced by genetic variants in their cholinergic systems.
In her study, Grazioplene and her colleagues studied variations in the CHRNA4 gene, a key cholinergic receptor and determinant of whether you see the aforementioned kinds of "expected uncertainty" as threatening or exciting.
It wouldn't be enough to say this genetic variant was the sole determinant, though, so the study also examined how, in conjunction with the variation in the CHRNA4 gene, an individual's upbringing and social environment affected how he or she perceived uncertainty.
To study the functions of this variation, the researchers set up a week-long camp for 614 children, ages 8 through 13, all of whom came from the same socioeconomic background, but had different upbringings: Half of the children had an upbringing in which they had been maltreated with neglect or emotional, sexual or physical abuse, and the other half had an upbringing in which they had not been maltreated.
The children with the genetic variation who grew up in an abusive environment were more likely to perceive the new camp environment as threatening, and the children with the same genetic variation who had grown up in a normal environment were more likely to perceive the new environment as intriguing. Even more interestingly, these results were true regardless of age, sex or race.
Now, what does this mean? It means that, yes, there is certainly a genetic variant that makes you more inclined to be anxious or curious in new environments, but your upbringing and social environment play a role in determining which one of those two it will be.
And while this specific genetic variant is rare -- only one percent of the population actually have it -- it gives valuable insight into the way psychologists and scientists study behavioral patterns in relation to both genetics and environment.
So, if you've sobbed during "The Notebook," impulsively shared a video on Facebook of a kitten rolling around in a patch of grass that made you tear up or found yourself crying with your best friend when her boyfriend dumped her, take comfort in the fact that you were probably born this way -- feels and all.