By what age do children recognise that plagiarism is wrong?

To view plagiarism as an adult does, a child must combine several pieces of a puzzle: they need to understand that not everyone has access to all ideas; that people can create their own ideas; and that stealing an idea, like stealing physical property, is wrong.

There's been plenty of research on children's understanding of physical property ownership, which has shown that a rudimentary understanding is already in place by age two. Now in the first ever systematic study of its kind, Kristina Olson and Alex Shaw at Yale have investigated children's understanding of the ownership of ideas.

Across three studies, Olson and Shaw presented children aged between three and eleven with vignettes and puppet videos in which two characters either both came up with their own idea for what to draw in art class, or one character copied what the other one had drawn. By age five to six, children showed less liking for characters who copied and rated them as 'more bad'. Crucially, they gave copying as their justification for these negative appraisals. 'These results demonstrate a relatively sophisticated understanding of ideas as early as age five years,' the researchers said.

By contrast, three- to four-year-olds did not rate characters who copied as any less likeable or any more bad than characters who came up with their own ideas. In a control condition, children of this age gave negative ratings to characters who stole physical property, thus showing that the the null result for stealing ideas wasn't because the children didn't understand the rating scale or weren't paying attention.

Future research is needed to find out if children younger than four don't understand the idea of original ideas or if they don't yet recognise that to steal ideas is wrong (or both). It's also not yet clear what drives the development of understanding in this area - is it a reflection of cognitive development or does it perhaps have to do with exposure to formal rules about copying at school. 'Our hope is that our idea about ideas is unique and will motivate future research,' the researchers concluded.
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Olson, K., and Shaw, A. (2010). ‘No fair, copycat!’: what children’s response to plagiarism tells us about their understanding of ideas. Developmental Science DOI: 10.1111/j.1467-7687.2010.00993.x