Cryptomnesia represents an intriguing type of mental illusion in which peop
le mistakenly believe that they have produced a new idea when in fact they
have simply unwittingly retrieved an old, previously encountered idea from
memory. Drawing on recent research on this form of inadvertent plagiarism,
we hypothesized that perceivers' susceptibility to the illusion that other
people's responses were actually self-generated would be influenced by cont
extual variables that impact upon the efficiency of source monitoring. The
results of three studies, examining different contextual factors (i.e., Exp
eriment 1, perceptual similarity; Experiment 2, cognitive distraction; Expe
riment 3, retrieval context), confirmed this prediction. We consider how di
fficulties in source monitoring may inform our understanding of the process
and consequences of cryptomnesia in everyday life.