Double Misinformation: Effects on Eyewitness Remembering

General Audience Summary This research extends existing research on the impact of post-event misinformation on eyewitness memory. After witnessing an event, eyewitnesses may be exposed to misinformation (e.g., from other witnesses, the media, and possibly even the police), which has the potential to distort how the witnesses remember the event at a later point in time (e.g., when making a statement). This is long known (e.g., through Elizabeth Loftus and colleagues' groundbreaking work) and has been investigated and confirmed in hundreds of studies. Our new contribution to this field is to draw attention to a possible real-life situation that (to our knowledge) has never been investigated in eyewitness misinformation research: What happens if witnesses are exposed to multiple pieces of misinformation that contradict each other (in addition to contradicting a detail of the original event)? For example, a Volvo that was involved in a witnessed car accident might be described by a co-witness as a Peugeot and by still another co-witness as a Toyota. There is potential for this to happen: Often, there are multiple witnesses to crimes/accidents, and extending beyond the eyewitness case there is certainly a lot of partly contradictory misinformation on social media, etc. We reasoned that becoming aware of inherent contradictions between pieces of misinformation may reduce the credibility of the misinformation and thus limit its impact on memory. This is partly what we found in three studies-but we also found an opposite process: When misinformation is more subtle and less likely to be noticed in the first place, then being exposed to multiple pieces of misinformation increases the chances that at least one of them will be noticed and subsequently incorporated in the witness's memory. Our study highlights the complex effects of multiple misinformation and suggests that further exploration of this intriguing phenomenon is worthwhile. Eyewitnesses may be exposed to multiple, mutually contradictory pieces of misinformation. In the simplest case of double misinformation, an original detail is targeted by misinformation A and then by misinformation B, which contradicts A. In such situations, two separate mechanisms may produce opposite effects on eyewitness remembering: (1) multiple chances to be misled enhance the misinformation effect and (2) noticing contradictions between multiple pieces of misinformation undermines credibility and decreases the effect (all relative to the effect of a single piece of misinformation). Across three experiments, we found support for both of these effects and confirmed an important moderating factor in an item analysis: The first mechanism dominates at low levels of misinformation (encoding and subsequent) availability, and the second at high levels (as this facilitates noticing contradictions). This means that, ironically, more misinformation can be less effective (in terms of distorting eyewitness memory or factual knowledge) if it contradicts itself.