Chris Kidd

In the first study, the researchers found that materialism increases during the younger ages but declines near the end of the high school years.

"The level of materialism in teens is directly driven by self-esteem," John said. "When self-esteem drops as children enter adolescence, materialism peaks. Then, by late adolescence, when self-esteem rebounds, their materialism drops."

In the second study, the young people received paper plates with positive descriptions about them, such as "smart" and "fun," by their peers in a summer camp setting.

The study ... found this seemingly small gesture sharply reduced the high levels of materialism found among 12- and 13-year-olds- and the moderate levels of materialism among 16- to 18-year-olds.