This research investigated the hypothesis that metacognitive inferences in source memory judgements are based on the recognition or nonrecognition of an event together with perceived or expected differences in the recognizability of events from different sources. The hypothesis was tested with a multinomial source-monitoring model that allowed separation of source-guessing tendencies for recognized and unrecognized items. Experiments 1A and 1B manipulated the number of item presentations as

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... vant source information and revealed differential guessing tendencies for recognized and unrecognized items, with a bias to attribute unrecognized items to the source associated with poor item recognition. Experiments 2A and 2B replicated the findings with a manipulation of presentation time and extended the analysis to subjective differences in item recognition. Experiments 3A and 3B used more natural source information by varying type of acoustic signal and demonstrated that subjective theories about differences in item recognition are sufficient to elicit differential source-guessing biases for recognized and unrecognized items. Together the findings provide new insights into the cognitive processes underlying source memory decisions, which involve episodic memory and reconstructive tendencies based on metacognitive beliefs and general world knowledge.