(PhysOrg.com) -- Your 7-year-old may understand that a positive attitude is an asset when taking a spelling test, doing a math problem or tackling a science lesson. But don't expect a kindergartner to make that link.

A new study by researchers at UC Davis and the University of Washington found that while 5-, 6- and 7-year-olds all understood that and poor physical habits (like skipping breakfast) can lead to poorer , only the 7-year-olds recognized the link between and doing well in school.

The study appeared in the January/February issue of , the journal of the Society for Research in Child Development.

"For the younger , seeing the tie between positive emotions and school performance was difficult," said Kristin Lagattuta, assistant professor of psychology at UC Davis and one of the study's authors. "It was harder for them to grasp how positive would lead to doing well in school."

The sooner children learn to make that connection, the better they will be able to prepare for and control their school performance, she said.

Just as parents teach kids the importance of getting a good night's and eating a good breakfast, they may want to talk with children about the importance of positive emotions like confidence and optimism, the research suggests.

Provided by UC Davis