Positive thoughts seem to increase connections between regions of the brain in favorable ways. But the study, published in The Journal of Neuroscience, showed that optimism can also come with risks.
"We were interested to show the science behind an old phenomenon, called the optimism bias," said co-author, Dr. Bojana Kuzmanovic, Cognitive neuroscientist at Max Planck Institute for Metabolism Research, in an interview with ABC News. "What we conclude and believe depends on what we want to believe."
To see how optimistic beliefs influenced their brain activity, researchers from Germany and Switzerland looked at fMRI brain images and analyzed survey responses using computer models from 24 self-described positive thinkers, 10 men and 14 women.
When learning new information, these people were more likely to incorporate good news than bad news into their overall belief systems. The good news increased the activity in the reward region of the participants' brains. When the participants rejected bad news, the same reward region also showed increased activity. Plus, the reward regions of their brains increased connections to other thought-processing, or cognitive, areas of their brains.
The stronger the individual's original optimism bias was, the stronger the connections were between the cognitive areas of their brains.
Although increased activity in the reward centers and increased neural connections might sound great, there was an important caution noted in the study.
The optimism bias -- a thought process that leads people to believe that they are less likely to run into a negative event than other people -- was strong. In other words, optimistic people can believe "bad stuff only happens to other people."
This bias can have a strong unconscious influence, preventing people from taking precautionary measures when making important decisions.
"Even politicians making big decisions could be using this bias," said Kuzmanovic. "It is important to consider an alternative viewpoint, especially when you really care about the outcomes, and there is a lot at stake."
There are some other factors that researchers noted could have influenced the effects on participant's brains. Some ideas could have been especially positive for certain individuals because of their tastes or experiences and it's possible that hearing good news directly after bad news made it even better.
Kuzmanovic acknowledged that the implications of this phenomenon are not all bad. Previous studies have shown that incorporating positive thoughts into beliefs can lead to better cardiovascular health and an improvement in a person's overall ability to cope with stress.
"People do have positive value for their positive beliefs," said Kuzmanovic. "It is just about being aware. These influences are present in all the decisions we make, and may put us in danger of making biased decisions. When making important decisions, we should consider collaborating with others to understand different perspectives."
Richa Kalra, M.D., is a resident physician specializing in psychiatry and working in the ABC News Medical Unit.