False memories in forensic psychology: do cognition and brain activity tell the same story?

One of the most important problems in forensic psychology is the impossibility of reliably discriminating between true and false memories when the only prosecution evidence comes from the memory of a witness or a victim. Unfortunately, both children and adults can be persuaded that they have been victims of past criminal acts, usually of a sexual nature. In adults, suggestion often occurs in the context of suggestive therapies based on the belief that traumatic events are repressed, while children come to believe and report events that never occurred as a result of repeated suggestive questioning. Cognitive Researchers have designed false memory paradigms (i.e., misinformation effect, Deese-Roediger-McDermott paradigm, event implantation paradigm) to first form false memories and then determine whether it is possible to reliably differentiate between false and true memories. In the present study, we review the contribution of cognitive research to the formation of false memories and the neuropsychological approaches aimed to discriminate between true and false memories. Based on these results, we analyze the applicability of the cognitive and neuropsychological evidence to the forensic setting.

"I heard it before or not": time-course of ERP response and behavioural correlates associated with false recognition memory.

Electrophysiological and behavioural correlates of true and false memories were examined in the Deese/Roediger-McDermont (DRM) paradigm. A mass univariate approach for analysing event-related potentials (ERP) in the temporal domain was used to examine the electrophysiological effects associated with this paradigm precisely (point-by-point) and without bias (data-driven). Behaviourally, true and false recognition did not differ, and the predicted DRM effect was observed, as false recognition of critical lures (i.e., new words semantically related to studied words) was higher than false alarms of new (unrelated) words. Neurally, an expected old/new effect was observed during the time-range of the late positive component (LPC) over left centro-parietal scalp electrodes. Furthermore, true recognition also evoked larger LPC amplitudes than false recognition over both left centro-parietal and fronto-central scalp electrodes. However, we did not observe LPC-related differences between critical lures and new words, nor between correct rejections of critical lures and new words. In contrast, correct rejections of critical lures were accompanied by higher activation of a sustained positive slow wave (SPSW) in right fronto-central electrodes beyond 1200 ms. This result reveals a key role of post-retrieval processes in recognition. Results are discussed in light of theoretical approaches to false memory in the DRM paradigm.

How Chronological Age, Theory of Mind, and Yield are Interrelated to Memory and Suggestion in Young Children.

We investigated the interrelations between chronological age, theory of mind (ToM), Yield (as a measure of individual suggestibility), memory and acceptance of experimental suggestion in a sample of children between 3 and 7 years old (N = 106). One week after participants interacted with 'a Teacher', they were asked to recall activities carried out with the Teacher (direct experience) and the contents of a story read to them by the Teacher (indirect experience). Data were examined with an analysis of developmental trajectories, which allows establishing the predictor value of socio-cognitive developmental factors regardless of participants' chronological age. It also estimates predictor values in interaction with the age and determines whether age is the best predictor for performance. As in previous research, results showed that chronological age was the main predictor of memory performance, both for direct experience (i.e., activities performed) and indirect experience (i.e., contents of the story). However, ToM and Yield, together with participants' ages, modulated their acceptance of the external suggestions received (presented only once, one week after the event). A turning point was observed at age 4.6. Below this age, the greater the mentalist skills (higher ToM), the lower was the vulnerability to external suggestion. Still, children below this age characterized individually as being suggestible (Yield medium or high) were more vulnerable to suggestion the younger they were. Thus, developmental socio-cognitive factors might modulate young children's vulnerability to external suggestions, even if received only once.

False recollections and the congruence of suggested information.

In two experiments, congruence of postevent information was manipulated in order to explore its role in the misinformation effect. Congruence of a detail was empirically defined as its compatibility (or match) with a concrete event. Based on this idea it was predicted that a congruent suggested detail would be more easily accepted than an incongruent one. In Experiments 1 and 2 two factors(congruence and truth value ) were manipulated within-subjects, and a two-alternative forced-choice recognition test was used followed by phenomenological judgements. Furthermore, in the second experiment participants were asked to describe four critical items (two seen and two suggested details)to explore differences and similarities between real and unreal memories. Both experiments clearly showed that the congruence of false information caused a robust misinformation effect, so that congruent information was much more accepted than false incongruent information. Furthermore, congruence increased the descriptive and phenomenological similarities between perceived and suggested memories, thus contributing to the misleading effect.