Misattributing post-event causal suggestions to the original story event: Rates of false memory for human and physical causes of negative outcomes

Source confusions between witnessed events and post-event suggestions are more likely to occur when the suggested information helps to explain the causal factors that contributed to the event's outcome. With evidence suggesting that human involvement in a causal chain (either deliberate or unintentional) is a more "satisfying" explanation than the involvement of a purely physical agent (such as wear-and-tear or weather,) the current study sought to answer whether such false memory formation might occur at higher rates for post-event suggestions of human causes than for suggested physical causes. Experiment 1 tested this hypothesis by providing 139 university undergraduate participants with original story events in audio narrative form, then introducing a post-event suggestion regarding a human-deliberate, human-unintended, or purely physical cause for the story outcome, and finally assessing source misattributions through a free recall task. Participants reliably misremembered all three types of post-event causal suggestion as having been part of the original story event, but as predicted, the likelihood of falsely recalling causal post-event information depended on the type of cause that was suggested, with suggested human causes -- either deliberate or unintended -- being misattributed to the original event at higher rates than suggested physical causes. Experiment 2 examined the hypothesis in a sample of 105 university undergraduates with a recognition source test instead of a free recall task. While there was a significant effect of post-event suggestion versus control (no additional causal information,) participants did not misremember human causes as having been part of the original event at a higher rate than physical, as they had in Experiment 1. The results of Experiment 1 clearly support the hypothesis, but the results of Experiment 2, while not altogether inconsistent with the underlying expectations, raise perplexing possibilities that beg further investigation. Follow-up data supported the idea that the difference between types of causes in Experiment 1 may reflect a difference in the perceived "newsworthiness" of the misattributed human and physical causal material. Human causes were judged as less likely than the physical causes to bring about the given outcome by participants who were asked to consider all three causal possibilities. Those causes which were viewed as least likely were, when provided in the form of post-event suggestion and misattributed to the original story, most likely to be freely reported.