Controversy surrounds the relationship between the three Synoptic Gospels written by Mark, Matthew and Luke. In particular, researchers on the New Testament disagree about whether the similarities between these three Gospels can be attributed to copying from a common information source, or whether they are due to a reliance on common oral traditions. Two experiments were conducted to investigate the characteristics that might distinguish material that was orally transmitted from that which was copied. In Experiment 1, participants were asked to write short narratives about recent and historic events, using (a) no external sources (b) an external source which was to be returned before the narrative was written, or (c) an external source which was retained while the narrative was written. Results showed that long sequences of common verbatim text occurred only when external sources could be retained while the account was written, suggesting behaviour indicative of copying. In Experiment 2, however, different genres of material were examined (jokes, aphorisms, and poetry). Results showed that while long sequences of more than 18 words in verbatim sequence might be evidence of copying where narrative material is concerned, it is not necessarily true for poetry or aphorisms, where it is possible to transmit from memory more than 18 words in exact sequence. We conclude that when Gospel instances of long sequences of similar material are examined, copying is a likely explanation. But such instances only represent a small proportion of the total number of parallels. The majority of parallel traditions appear to rely on memory, consistent with the experimental evidence presented here. Copyright © 2004 John Wiley & Sons, Ltd.