How Witnesses Remember Crimes: The Role of Cognitive Resources and Deception on Memory

Within the legal realm, testimonies are oftentimes the only piece of evidence that legal professionals (e.g., judges, jury) rely on when rendering a legal decision. However, testimonies are not necessarily accurate reports of the crime. The reason is because testimonies are basically memories that witnesses, suspects, or victims have about an experienced event. The recollection of an event can be affected by many factors (e.g., cognitive resources, lying, emotions). Moreover, some scholars have demonstrated that individuals’ cognitive resources are one of the factors that can influence the memory for an event. Other scholars have argued that cognitive resources implicated when someone deceives someone can be another factor implicated in how people honestly remember the event. Liars can adopt different deceptive strategies (i.e., false denials, feigned amnesia, and fabrication) and each of them requires a different amount of cognitive resources. However, research investigating the role of the cognitive resources on witnesses’ memory is still quite limited, especially regarding memories of witnesses that lied during an investigation and later came forward with the truth. In the current dissertation, I present evidence of a series of experimental studies that sheds new light on how cognitive resources are involved in recollection of an event. In Chapter 2, I describe an experiment to examine how the availability of cognitive resources (i.e., low or high) -- in terms of Executive Functions (EF) -- affects the genuine recall of witnesses. The study showed that having a high amount of EF resources makes people more able to correctly report event-related details and, at the same time, protects from memory distortions (i.e., omission and commission errors). In Chapter 3, I present further evidence showing that, in specific circumstances, the individuals’ availability of EF resources is not indicative of memory accuracy. In particular, the study aimed to verify whether individuals’ EF resources (i.e., low or high) can also be informative of the memory impairment (i.e., forgetting, memory distortions) followed to the act of lying (i.e., falsely denying and fabricating). Findings show that this was not the case. Indeed, as I show in Chapters 4, 5, and 6, liars’ memory performance is differentially affected by the kind of deception adopted. Specifically, in Chapter 4, I show that false denials -- that scholars have assumed to be the less demanding deceptive strategy – can lead to various effects on memory (i.e., forgetting for the interview or for the event) with regards to the cognitive resources employed during the denials. The effects of two different false denials (i.e., complex or simple) have been tested in this study. Findings supported the idea that cognitive resources implicated to execute the lie divergently impacted deniers’ memory. An impairment for the memory for the event was found for complex deniers, while a strong undermining for the recollection of the interview (i.e., denial-induced forgetting effect) was replicated in simple deniers. Support to the assumption that the cognitive load associated with lying influences liars’ memory performance was found in Chapter 5. Here, I tested the effects of two different types of fabrication strategy (i.e., distortion or fabrication) on memory. Liars adopting the less demanding strategy (i.e., distortion) reported a stronger impairment of the memory for the interview than liars adopting the more demanding strategy (i.e., fabrication), that, by contrast, had a lower recall of the memory for the event. In Chapter 6, I present the last study run to assess whether the cognitive load associated with the act of repeatedly lying (i.e., denying and fabricating) can increase the typical effects of lying on memory. Evidence of this study seems to suggest that indeed liars have more difficulty to remember details repeatedly lied upon than details lied just once. All findings illustrated in the current dissertation clarify the role of cognitive resources on witnesses’ memory. Specifically, I showed that cognitive resources give important information on the reliability of witnesses’ reports. Thus, I have underlined the need for legal professionals (e.g., judges, criminologists) to consider such a factor when called to asses the statements reliability of witnesses.