From Yale: Children's responses to plagerism

http://www.ncbi.nlm.nih.gov/pubmed/22213911

Dev Sci. 2011 Mar;14(2):431-9.
‘No fair, copycat!’: what children’s response to plagiarism tells us about their understanding of ideas.
Olson KR, Shaw A.
Source
Department of Psychology, Yale University, New Haven, CT 06520, USA. kristina.olson@yale.edu

Abstract
Adults believe that plagiarizing ideas is wrong, which requires an understanding that others can have ideas and that it is wrong to copy them. In order to test when this understanding emerges, we investigated when children begin to think plagiarism is wrong. In Study 1, children aged 7, 9 and 11 years old, as well as adults, disliked someone who plagiarized compared to someone who drew an original drawing or someone who drew an identical picture by chance. Study 2 investigated the same question with younger children, focusing on children aged 3–6 years old. Children aged 5–6 years old evaluated plagiarizers negatively relative to unique drawers, but 3–4-year-olds did not. Study 3 replicated the findings from Study 2 and found that children justify their negative evaluations of plagiarizers by mentioning concerns over copying. These experiments provide evidence that, by age 5 years old, children understand that others have ideas and dislike the copying of these ideas.