For some of us, every day is a constant yo-yo from enthusiastic to miserable. While others maintain an even keel, we're eternally on the verge of hysteria.
According to researchers, a very specific gene seems to be the determining factor in the way we perceive stimuli.
In a previous study, Professor Rebecca Todd proved people with the ADRA2b deletion variant are more likely to perceive negative words, images and ideas than their fellows without it.
The gene influences the production of norepinephrine, a hormone key to the fight-or-flight response.
More recently, Todd used 39 brain scans to understand the cranial activity of those who see more negative influences.
Imaging indicated the part of the brain dedicated to controlling emotion -- as well as the section that perceives threat -- was more active in the 21 participants who had the gene variant.
The study's senior author, Adam Anderson, explained in a press release,
Emotions are not only about how [you] feel about the world, but how our brains influence our perception of it. As our genes influence how we literally see the positive and negative aspects of our world more clearly, we may come to believe the world has more rewards or threats.
The gene variant creates something called "emotionally enhanced vividness," and that might help explain why trauma is more acute for some patients.
On a lesser scale, the variant might have us perceiving negative stimuli that aren't even really there.
You can thank your parents for passing those genes along.