Denying traumatic experiences - how false denials might impact false memory formation

Perpetrators, victims, and witnesses sometimes falsely deny events even though they truly experienced them, for various socio-emotional and motivational reasons. However, someone who initially denied a crime they witnessed, suffered, or perpetrated might come forward with allegations of what happened and give testimony in court, for example. The general aim of this dissertation was to examine the effects of false denials on the validity of memory-based testimony by 1) investigating how often false denials occur, 2) what the mnemonic consequences of false denials are for different legally relevant actors who might use false denials, 3) how false denials in social settings can affect memory, and 4) what the practical applicability of this research is.

            In Part I (Chapters 1 and 2), the background and relevance of false denials in the legal system are discussed. Chapter 1 introduces the topic of false denials and summarizes previous research into the memory effects of false denials. Moreover, it is discussed these memory effects interact with false memory and social memory theories. Chapter 1 also highlights possible miscarriages of justice that might follow from the mnemonic consequences of false denials and why it is important to study the effects of false denials on memory-based testimonies. Chapter 2 describes prevalence rates of false denials among 68 children who were interviewed in potential cases of abuse at the Dutch child protection service “Veilig Thuis”. Beyond finding that false denials were common among victims in confirmed abuse cases (i.e., 40%, 19/ 48), Chapter 2 also revealed that false denials happened even in interviews that followed evidence-based best practice guidelines (i.e., the NICHD interview). This finding means that the vast variance in denial rates in previous research might be unrelated to the interviewing strategies used, despite arguments by some disclosure researchers. The overarching conclusion of Part I was that false denials are a common occurrence in the legal arena.

            Part II (Chapters 3, 4 and 5) built on this insight and focused on the impacts of false denials brought forward from a victim, witness, and perpetrator perspective on both conversational and eyewitness testimony using experimental methodologies. To this end, Chapter 3 investigated how simulated false denials of a child abuse narrative in which participants roleplayed being the victim affected their memory-based reports later on. Chapter 3 failed to replicate previously found memory effects, but revealed that participants who falsely denied abuse were more likely to endorse suggested false details later on. In Chapter 4, I examined false denials for performed actions, in line with the type of events a perpetrator might deny. Chapter 4 revealed that it was almost impossible for participants to forget actions they had previously performed, even if the denied having committed them repeatedly.

The last Chapter of Part II, Chapter 5, investigated the mnemonic effects of falsely denying a negative witnessed event. Chapter 5 replicated the denial-induced forgetting effect, meaning that participants who falsely denied having seen certain details in the trauma analogue video were more likely to forget that they had previously denied these details compared with participants who were consistently honest. Additionally, Chapter 5 found that participants who falsely denied were more prone than honest participants to reporting suggested false information for the time point at which participants denied. Taken together, Part II showed that false denials can undermine memory for discussions around a witnessed event and may also increase the reporting of false information regarding the event. However, this can only be generalized to witnessed actions, not self-referenced information or performed actions.

Part III of this doctoral dissertation increased the practical applicability of this research line further by taking into account the social context in which false denials can occur. That is, Chapter 6 focused on how false information conveyed by a co-witness would affect the memory reports of a witness who initially denied having seen a very negative event, and came forward while talking to the co-witness. In Chapter 6, the denial-induced forgetting effect was replicated and participants who had previously denied witnessed details were more likely to adopt false information from the co-witness compared with honest witnesses. Another social context in which false denials might occur was investigated in Chapter 7. Specifically, Chapter 7 examined memory effects of false denials of an assault that were put forward during an informal conversation among co-witnesses. Chapter 7 found no evidence that denial-induced forgetting applies in such informal settings. Part III can be concluded by stating that witnesses who initially deny information in a formal setting, such as an interview, and then came forward can be more prone to memory errors, but denials might not have such effects when they happen during informal conversations.

            Part IV assessed the practical relevance of false denials in the courtroom. Specifically, Chapter 8 evaluated via which route false denials affect memory-based testimony (i.e., via a response bias or by changing the memory trace). A signal detection theory and ROC curve analysis revealed that regarding memory for previous discussions, false denials affected memory strength itself. Chapter 8 also revealed that any effects of false denials on true memory for the witnessed trauma analogue event are not practically meaningful in a legal context, if we consider a difference of minimally one detail practically meaningful. Chapter 9 examined researchers (e.g., oftentimes also expert witnesses) and child protection workers’ beliefs about child abuse disclosure and statement validity to examine whether there is any consensus in the relevant professional community. The latter is important for evidence to enter the court room. Chapter 9 revealed that professionals believed that false denials, and inconsistent reporting, could negatively affect the validity of testimony, but that testimony given after false denials should be admissible as evidence in court. Specifically, there was agreement regarding these elements, and for example for the idea that false denials can occur.

Last, in Chapter 10, the most critical findings of Chapters 2-9 were discussed. Moreover, it was assessed whether the results meet memory expert witnesses’ requirements of being replicated, generalizable, and practically meaningful. Taken together, this dissertation showed that false denials of witnessed events can negatively impact memory-based testimonies in a legal setting.