Researchers found that some people see the "glass as half empty" due to the presence of a certain genetic variant.

The study, conducted by researchers at the University of British Columbia, found that people with ADRA2b deletion variant are more likely to brood over otherwise petty issues. Previous studies have shown that about half of all Caucasians have this gene variant while its prevalence in other ethnicities ( such as people living in Rwanda) is less than 10 percent.

"This is the first study to find that this genetic variation can significantly affect how people see and experience the world," says Prof. Rebecca Todd of UBC's Dept. of Psychology in a news release. "The findings suggest people experience emotional aspects of the world partly through gene-coloured glasses - and that biological variations at the genetic level can play a significant role in individual differences in perception."

Previous research has shown that the gene variant plays an important role in hormone and neurotransmitter norepinephrine.

Norepinephrine is a stress hormone and works with epinephrine in regulating the fight or flight response.

In the present study, 200 people were shown positive, negative and neutral words in a rapid succession. Researchers found that people with the ADRA2b gene variant were more likely to catch the negative words than others.

"These individuals may be more likely to pick out angry faces in a crowd of people," says Todd. "Outdoors, they might notice potential hazards - places you could slip, loose rocks that might fall - instead of seeing the natural beauty."

The study," Genes for emotion-enhanced remembering are linked to enhanced perceiving," is published in the journal Psychological Science, 2013.