From MSNBC:
“Nah,” “eh,” “no” and “ugh”: These are the familiar sounds of people who don't seem to like much and conjure negative quips for just about anything. While people with more positive dispositions may try to shake enthusiasm unto these downers, new research helps to explain why this often doesn't work. That certain people like more things than others may seem obvious, but, until now, nobody has ever tested whether such dispositions operate as distinct personality traits, separate from other traits such as optimism/pessimism or extroversion/introversion. A team of researchers from the University of Illinois at Urbana-Champaign and the University of Pennsylvania have now conducted the first quantitative analysis of dispositional attitude, finding that it is, in fact, distinct from these other traits. “Optimists tend to have generalized beliefs usually about the future, such as 'Things are going to turn out well,'” said Justin Hepler, a professor of psychology at the University of Illinois at Urbana-Champaign and an author on the study. “We were interested in whether people liked or disliked things, in general, and had people report their attitude about different things.”
…The researchers found that people's dispositional attitudes often correlated with other similar traits, but were still statistically distinct, meaning that some optimists have a tendency to dislike many things, and some pessimists, likewise, might like lots of things. As with all personality traits, dispositional attitudes develop through a combination of one's biology and environment. The team has not yet assessed how therapy could help mediate these traits, but suggests that adjusting one's external stimuli, such as surrounding oneself with positive people, could ultimately sway a person from one side of the spectrum to the other.
More here.