  Mobile phones contain a wealth of private information, so we try to keep them
secure. We provide large-scale evidence that the psychological profiles of
individuals and their relations with their peers can be predicted from
seemingly anonymous communication traces -- calling and texting logs that
service providers routinely collect. Based on two extensive longitudinal
studies containing more than 900 college students, we use point process
modeling to describe communication patterns. We automatically predict the peer
relationship type and temporal dynamics, and assess user personality based on
the modeling. For some personality traits, the results are comparable to the
gold-standard performances obtained from survey self-report data. Findings
illustrate how information usually residing outside the control of individuals
can be used to reconstruct sensitive information.
