In three experiments we investigated cryptomnesia (unconscious plagiarism) and source memory using a word-search puzzle task. Subjects first alternated with a "computer partner" in locating words from 4 puzzles. They then attempted to recall their previously generated items as well as to locate additional new words. Substantially more plagiarism was committed in these tasks than was observed in a study by A. S. Brown and D. R. Murphy (1989), in which Ss generated category exemplars. Manipulations of retention interval (Experiment 1) and degree of encoding (Experiments 2a and 2b) reliably influenced plagiarism rates. Source confusions from a modified recognition memory task (Experiment 3) were used as the basis for a unitary relative strength model to explain both source and occurrence (item) forgetting.