  Children and adolescents interact in peer groups, which are known to
influence a range of psychological and behavioral outcomes. In developmental
psychology and related disciplines, social cognitive mapping (SCM), as
implemented with the SCM 4.0 software, is the most commonly used method for
identifying peer groups from peer report data. However, in a series of four
studies, we demonstrate that SCM has an unacceptably high risk of false
positives. Specifically, we show that SCM will identify peer groups even when
applied to random data. We introduce backbone extraction and community
detection as one promising alternative to SCM, and offer several
recommendations for researchers seeking to identify peer groups from peer
report data.
