Researchers from the Ohio State University in US and Universidad Autonoma de Madrid in Spain found that when people wrote down their thoughts on a piece of paper and then threw the paper away, they mentally discarded the thoughts as well.
On the other hand, people were more likely to use their thoughts when making judgements if they first wrote them down on a piece of paper and tucked the paper in a pocket to protect it.
"However you tag your thoughts - as trash or as worthy of protection - seems to make a difference in how you use those thoughts," said Richard Petty, co-author of the study.
"At some level, it can sound silly. But we found that it really works - by physically throwing away or protecting your thoughts, you influence how you end up using those thoughts. Merely imagining engaging in these actions has no effect," Petty said in a statement.
The findings suggest that people can treat their thoughts as material, concrete objects, Petty said.
In an experiment, 83 Spanish high school students participated in a study where they wrote down either positive or negative thoughts about their body during a three-minute period.
All the participants were asked to look back at the thoughts they wrote. Researchers told half of the students to contemplate their thoughts and then throw them in the trash can located in the room, "because their thoughts did not have to remain with them".
The other half were told to contemplate their thoughts and check for any grammar or spelling mistakes. The participants then rated their attitudes about their own bodies.
Results showed that for those who kept their thoughts and checked them for mistakes, it mattered whether they generated positive or negative thoughts about their bodies.
Participants who wrote positive thoughts had more positive attitudes toward their bodies a few minutes later than did those who wrote negative thoughts.
However, those who threw their thoughts away showed no difference in how they rated their bodies, regardless of whether they wrote positive or negative thoughts.
"When they threw their thoughts away, they didn't consider them anymore, whether they were positive or negative," Petty said.
In two other experiments also researchers found that participants who kept the list of thoughts with them were more influenced when evaluating anything than those who threw their thoughts away.
The study was published in the journal Psychological Science.