Henry Otgaar

True or false? Memory is differentially affected by stress-induced cortisol elevations and sympathetic activity at consolidation and retrieval

Adrenal stress hormones released in response to acute stress may yield memory-enhancing effects when released post-learning and impairing effects at memory retrieval, especially for emotional memory material. However, so far these differential effects of stress hormones on the various memory phases for neutral and emotional memory material have not been demonstrated within one experiment. This study investigated whether, in line with their effects on true memory, stress and stress-induced adrenal stress hormones affect the encoding, consolidation, and retrieval of emotional and neutral false memories. Participants (N=90) were exposed to a stressor before encoding, during consolidation, before retrieval, or were not stressed and then were subjected to neutral and emotional versions of the Deese-Roediger-McDermott word list learning paradigm. Twenty-four hours later, recall of presented words (true recall) and non-presented critical lure words (false recall) was assessed. Results show that stress exposure resulted in superior true memory performance in the consolidation stress group and reduced true memory performance in the retrieval stress group compared to the other groups, predominantly for emotional words. These memory-enhancing and memory-impairing effects were strongly related to stress-induced cortisol and sympathetic activity measured via salivary alpha-amylase levels. Neutral and emotional false recall, on the other hand, was neither affected by stress exposure, nor related to cortisol and sympathetic activity following stress. These results demonstrate the importance of stress-induced hormone-related activity in enhancing memory consolidation and in impairing memory retrieval, in particular for emotional memory material.

Valence and the development of immediate and long-term false memory illusions

Across five experiments we examined the role of valence in childrens and adults’ true and false memories. Using the Deese/Roediger-McDermott paradigm and either neutral or negative-emotional lists, both adults’ (Experiment 1) and childrens (Experiment 2) true recall and recognition was better for neutral than negative items, and although false recall was also higher for neutral items, false recognition was higher for negative items. The last three experiments examined adults’ (Experiment 3) and childrens (Experiments 4 and 5) 1-week long-term recognition of neutral and negative-emotional information. The results replicated the immediate recall and recognition findings from the first two experiments. More important, these experiments showed that although true recognition decreased over the 1-week interval, false recognition of neutral items remained unchanged whereas false recognition of negative-emotional items increased. These findings are discussed in terms of theories of emotion and memory as well as their forensic implications.

Adaptive Memory: Survival Processing Increases Both True and False Memory in Adults and Children.

Research has shown that processing information in a survival context can enhance the informations memorability. The current study examined whether survival processing can also decrease the susceptibility to false memories and whether the survival advantage can be found in children. In Experiment 1, adults rated semantically related words in a survival, moving, or pleasantness scenario. Even though the survival advantage was demonstrated for true recall, there also was an unexpected increase in false memories in the survival condition. Similarly, younger and older children in Experiment 2 displayed superior true recall but also higher rates of false memories in a survival condition. Experiment 3 showed that in adults false memories were also more likely to occur in the survival condition when categorized lists instead of Deese-Roediger-McDermott (DRM)-like word lists were used. In all three experiments, no survival recall advantage was found when net accuracy scores that take the total output into account were used. These findings question whether survival processing is an adaptive memory strategy per se, as such processing not only enriches true recall but simultaneously amplifies the vulnerability to false memories.

Picturing survival memories: Enhanced memory after fitness-relevant processing occurs for verbal and visual stimuli

Recent studies have shown that processing words according to a survival scenario leads to superior retention relative to control conditions. Here, we examined whether a survival recall advantage could be elicited by using pictures. Furthermore, in Experiment 1, we were interested in whether survival processing also results in improved memory for details. Undergraduates rated the relevance of pictures in a survival, moving, or pleasantness scenario and were subsequently given a surprise free recall test. We found that survival processing yielded superior retention. We also found that distortions occurred more often in the survival condition than in the pleasantness condition. In Experiment 2, we directly compared the survival recall effect between pictures and words. A comparable survival recall advantage was found for pictures and words. The present findings support the idea that memory is enhanced by processing information in terms of fitness value, yet at the same time, the present results suggest that this may increase the risk for memory distortions.

The ease of lying

Brain imaging studies suggest that truth telling constitutes the default of the human brain and that lying involves intentional suppression of the predominant truth response. By manipulating the truth proportion in the Sheffield lie test, we investigated whether the dominance of the truth response is malleable. Results showed that frequent truth telling made lying more difficult, and that frequent lying made lying easier. These results implicate that (1) the accuracy of lie detection tests may be improved by increasing the dominance of the truth response and that (2) habitual lying makes the lie response more dominant.

The Malevolent Side of Human Nature: A Meta-Analysis and Critical Review of the Literature on the Dark Triad (Narcissism, Machiavellianism, and Psychopathy)

The term dark triad refers to the constellation of narcissism, Machiavellianism, and psychopathy. Over the past few years, the concept has gained momentum, with many researchers assuming that the dark triad is a prominent antecedent of transgressive and norm-violating behavior. Our purpose in this meta-analytic review was to evaluate (a) interrelations among narcissism, Machiavellianism, and psychopathy; (b) gender differences in these traits; (c) how these traits are linked to normal personality factors; and (d) the psychosocial correlates of the dark triad. Our findings show that dark triad traits are substantially intercorrelated, somewhat more prevalent among men than women, predominantly related to the Big Five personality factor of agreeableness and the HEXACO factor of honesty-humility, and generally associated with various types of negative psychosocial outcomes. We question whether dark triad traits are sufficiently distinct and argue that the way they are currently measured is too simple to capture the malevolent sides of personality. Because most research in this domain is cross-sectional and based on self-reports, we recommend using a cross-informant approach and prospective, longitudinal research designs for studying the predictive value of dark triad features.

Experimentally evoking nonbelieved memories for childhood events

We report on the 1st experimental elicitation of nonbelieved memories for childhood events in adults (Study 1) and children (Study 2) using a modified false memory implantation paradigm. Participants received true (trip to a theme park) and false (hot air balloon ride) narratives and recalled these events during 2 interviews. After debriefing, 13% of adults and 15% of children reported nonbelieved memories. While phenomenal ratings were higher for true than for nonbelieved memories immediately after the debriefing, after a month nonbelieved memories behaved as true memories. Also following debriefing, 23% of adults and 15% of children retracted their false memory claims. Prior to debriefing, participants with nonbelieved memories were most likely to indicate remembering the event, whereas participants with false memories who retracted their claim were most likely to endorse believing but not remembering the event. This research suggests that debriefings in previous false memory studies can lead to the development of nonbelieved memories. Additional findings regarding the correspondence between subjective belief, subjective memory, and objective memory judgments prior to and following debriefing are discussed.

Proximate Mechanisms and the Development of Adaptive Memory

Scientific investigations into the functional properties of memory have recently undergone a rapid increase. These studies have revealed that processing stimuli for its survival value results in superior memory performance in children and adults. In this article, we critically evaluate this claim and conclude that survival-processing advantages in childhood and adulthood are not an indication that fitness-relevant information has adaptive priority. Instead, we argue that general memory principles (e.g., item-specific and relational processing, self-referential processing, elaboration and distinctiveness processing) better explain the adaptive function of memory. We stress the importance of these memory processes because they characterize the evolutionary adaptations of memory, are present early in life, and are developmentally invariant.

Script knowledge enhances the development of children’s false memories

We examined whether script knowledge contributes to the development of childrens false memories. Sixty 7-year-old and 60 11-year-old children listened to false narratives describing either a high-knowledge event (i.e., fingers being caught in a mousetrap) or a low-knowledge event (i.e., receiving a rectal enema) that were similar in terms of plausibility and pleasantness. Moreover, half of the children in each condition received additional suggestive details about the false events. Across two interviews, children had to report everything they remembered about the events. Script knowledge affected childrens false memories in that both younger and older children developed more false memories for the high-knowledge event than for the low-knowledge event. Moreover, at the first interview, additional suggestive details inhibited the development of childrens images into false memories.

On the Existence and Implications of Nonbelieved Memories

In this article, we review the state of knowledge about a previously-assumed-to-be-rare memory phenomenon called nonbelieved memories. Nonbelieved memories are a counterintuitive phenomenon in which vivid autobiographical memories are no longer believed to have happened even though vivid recollective features remain present. Such memories stand in contrast to the more typical situation that when events are recollected they are also believed to have genuinely occurred. We review data on the frequency, characteristics, and factors that contribute to the development of naturally occurring and laboratory-induced nonbelieved memories and discuss the relationships of nonbelieved memories with theories of autobiographical remembering and the study of remembering in applied domains.