The counterintuitive relationship between conceptual and perceptual similarities and eyewitness suggestibility

The tendency to confuse witnessed and suggested information can result in inaccurate eyewitness testimonies and convictions of innocent people. Studies that tested how similarities between witnessed and suggested information affect the tendency to confuse them reached inconsistent results. Here, we claim that there is a more complex and not necessarily linear relationship between similarity and memory distortions. Participants (164) viewed two subsequent stories, which varied in the conceptual and perceptual similarities between them. We found a significant interaction between conceptual and perceptual similarities. When we presented two conceptually different stories, perceptual similarity increased the suggestibility effect compared with perceptual dissimilarity. Conversely, when we presented two conceptually similar stories, perceptual similarity decreased suggestibility compared with perceptual dissimilarity. Accordingly, we suggest that similarity between two events may increase the suggestibility effect. However, counter-intuitively, once similarity reaches a certain threshold, the coherence level between the events reduces the tendency to confuse them.