Finally, the basic tenets of self-regulation theory suggest that parental autonomy granting ought to be related to students' achievement motivation, a hypothesis that is supported by a study examining the relationship between parental and teacher autonomy support and a small sample of adolescents in the U.S. and Russia (Chirkov & Ryan, 2001 - no differences in the pattern of relationships was found for Russian and U.S. students). The authors find that students whose parents provide greater autonomy have lower levels of extrinsic motivation and higher levels of identified regulation (a more self-regulated form of motivation). This study is cross-sectional in nature, and therefore should be interpreted with caution. However this study provides support for a relationship that has been identified in a number of studies using less direct measures of student motivation or with younger children or adults, and therefore should not be dismissed as invalid.