The effect of alcohol and repetition at encoding on implicit and explicit false memories

Hazy memories in the courtroom: A review of alcohol and other drug effects on false memory and suggestibility

Alcohol and other psychoactive drugs are oftentimes implicated in legal cases. A pertinent question herein is whether such substances might adversely affect testimonies of victims, eyewitnesses, or suspects by propelling the formation of false memory and increasing susceptibility to suggestion. In the current review, we amassed all available evidence on the effects of intoxication on false memory formation and suggestibility, including the substances alcohol, benzodiazepines, cannabis, stimulants, hallucinogens, and antipsychotics. Our review indicated that alcohol and cannabis under certain conditions increased the susceptibility to false memories and/or suggestion with effect sizes ranging from medium to large. When intoxicated during an event, alcohol is most likely to increase this susceptibility at high intoxication levels or after a delay, whereas cannabis exerts detrimental effects during acute intoxication but not necessarily once sober. For other substances, ecologically valid research separating different memory phases is needed. Overall, differences between substances regarding false memory effects exist, suggesting that a nuanced approach is needed when dealing with intoxicated individuals in a legal context.

Improving intoxicated witness recall with the Enhanced Cognitive Interview

RATIONALE

Witnesses and victims typically provide the central leads in police investigations, yet statistics from past research indicates in many instances these individuals are intoxicated.

OBJECTIVES

To date, however, no research has looked at how best to interview such witnesses to maximise the amount of accurate information they recall.

METHODS

In the present research, whilst on a night out, participants watched a videoed theft whilst either sober or moderately (MBAC = 0.05%) or severely (MBAC = 0.14%) intoxicated. A week later, in a different location, participants were interviewed using either the Enhanced Cognitive (ECI) or Structured Interview.

RESULTS

The ECI was found to improve the recall accuracy and completeness of witness accounts across all three drinking conditions. However, no significant interaction was indicated between alcohol and interview condition.

CONCLUSIONS

The study findings are discussed in terms of their real-world value in aiding police officers to elicit as complete and as accurate an account as possible from intoxicated witnesses.

An experimental examination of the effects of alcohol consumption and exposure to misleading postevent information on remembering a hypothetical rape scenario

We experimentally examined the effects of alcohol consumption and exposure to misleading postevent information on memory for a hypothetical interactive rape scenario. We used a 2 beverage (alcohol vs. tonic water) × 2 expectancy (told alcohol vs. told tonic) factorial design. Participants (N = 80) were randomly assigned to conditions. They consumed alcohol (mean blood alcohol content = 0.06%) or tonic water before engaging in the scenario. Alcohol expectancy was controlled by telling participants they were consuming alcohol or tonic water alone, irrespective of the actual beverage they were consuming. Approximately a week later, participants were exposed to a misleading postevent narrative and then recalled the scenario and took a recognition test. Participants who were told that they had consumed alcohol rather than tonic reported fewer correct details, but they were no more likely to report incorrect or misleading information. The confidence-accuracy relationship for control and misled items was similar across groups, and there was some evidence that metacognitive discrimination was better for participants who were told that they had consumed alcohol compared with those told they had tonic water. Implications for interviewing rape victims are discussed.

Do intoxicated witnesses produce poor facial composite images?

RATIONALE

The effect of alcohol intoxication on witness memory and performance has been the subject of research for some time, however, whether intoxication affects facial composite construction has not been investigated.

OBJECTIVES

Intoxication was predicted to adversely affect facial composite construction.

METHODS

Thirty-two participants were allocated to one of four beverage conditions consisting of factorial combinations of alcohol or placebo at face encoding, and later construction. Participants viewed a video of a target person and constructed a composite of this target the following day. The resulting images were presented as a full face composite, or a part face consisting of either internal or external facial features to a second sample of participants who provided likeness ratings as a measure of facial composite quality.

RESULTS

Intoxication at face encoding had a detrimental impact on the quality of facial composites produced the following day, suggesting that alcohol impaired the encoding of the target faces. The common finding that external compared to internal features are more accurately represented was demonstrated, even following alcohol at encoding. This finding was moderated by alcohol and target face gender such that alcohol at face encoding resulted in reduced likeness of external features for male composite faces only.

CONCLUSIONS

Moderate alcohol intoxication impairs the quality of facial composites, adding to existing literature demonstrating little effect of alcohol on line-up studies. The impact of intoxication on face perception mechanisms, and the apparent narrowing of processing to external face areas such as hair, is discussed in the context of alcohol myopia theory.

Effects of Sulpiride on True and False Memories of Thematically Related Pictures and Associated Words in Healthy Volunteers

Episodic memory, working memory, emotional memory, and attention are subject to dopaminergic modulation. However, the potential role of dopamine on the generation of false memories is unknown. This study defined the role of the dopamine D2 receptor on true and false recognition memories. Twenty-four young, healthy volunteers ingested a single dose of placebo or 400 mg oral sulpiride, a dopamine D2-receptor antagonist, just before starting the recognition memory task in a randomized, double-blind, and placebo-controlled trial. The sulpiride group presented more false recognitions during visual and verbal processing than the placebo group, although both groups had the same indices of true memory. These findings demonstrate that dopamine D2 receptors blockade in healthy volunteers can specifically increase the rate of false recognitions. The findings fit well the two-process view of causes of false memories, the activation/monitoring failures model.

Inert gas narcosis disrupts encoding but not retrieval of long term memory

Exposure to increased ambient pressure causes inert gas narcosis of which one symptom is long-term memory (LTM) impairment. Narcosis is posited to impair LTM by disrupting information encoding, retrieval (self-guided search), or both. The effect of narcosis on the encoding and retrieval of LTM was investigated by testing the effect of learning-recall pressure and levels of processing (LoP) on the free-recall of word lists in divers underwater. All participants (n=60) took part in four conditions in which words were learnt and then recalled at either low pressure (1.4-1.9atm/4-9msw) or high pressure (4.4-5.0atm/34-40msw), as manipulated by changes in depth underwater: low-low (LL), low-high(LH), high-high (HH), and high-low (HL). In addition, participants were assigned to either a deep or shallow processing condition, using LoP methodology. Free-recall memory ability was significantly impaired only when words were initially learned at high pressure (HH & HL conditions). When words were learned at low pressure and then recalled at low pressure (LL condition) or high pressure (LH condition) free-recall was not impaired. Although numerically superior in several conditions, deeper processing failed to significantly improve free-recall ability in any of the learning-recall conditions. This pattern of results support the hypothesis that narcosis disrupts encoding of information into LTM, while retrieval appears to be unaffected. These findings are discussed in relation to similar effects reported by some memory impairing drugs and the practical implications for workers in pressurised environments.

Ethanol-induced effects on sting extension response and punishment learning in the western honey bee (Apis mellifera)

Acute ethanol administration is associated with sedation and analgesia as well as behavioral disinhibition and memory loss but the mechanisms underlying these effects remain to be elucidated. During the past decade, insects have emerged as important model systems to understand the neural and genetic bases of alcohol effects. However, novel assays to assess ethanol's effects on complex behaviors in social or isolated contexts are necessary. Here we used the honey bee as an especially relevant model system since bees are typically exposed to ethanol in nature when collecting standing nectar crop of flowers, and there is recent evidence for independent biological significance of this exposure for social behavior. Bee's inhibitory control of the sting extension response (SER) and a conditioned-place aversion assay were used to study ethanol effects on analgesia, behavioral disinhibition, and associative learning. Our findings indicate that although ethanol, in a dose-dependent manner, increases SER thresholds (analgesic effects), it disrupts the ability of honey bees to inhibit SER and to associate aversive stimuli with their environment. These results suggest that ethanol's effects on analgesia, behavioral disinhibition and associative learning are common across vertebrates and invertebrates. These results add to the use of honey bees as an ethanol model to understand ethanol's effects on complex, socially relevant behaviors.

Memory for emotional picture cues during acute alcohol intoxication

OBJECTIVE

Memory affects behavior by allowing events to be anticipated and goals to be planned based on previous experiences. Emotional memory, in particular, is thought to play a central role in behavior in general and in drinking behavior in particular. Alcohol intoxication has been shown to disrupt intentional, conscious memory, but not unintentional, implicit memory for neutral stimuli; however, its effects on emotional memory are not well understood. This study examined whether alcohol intoxication affected memory for emotionally valenced stimuli by testing explicit recall and implicit repetition priming of emotional picture cues.

METHOD

Participants were 36 young adults (21-24 years old, 16 women) who received an alcohol, placebo, or no-alcohol beverage. Both cue exposure and memory testing occurred after beverage consumption (i.e., during intoxication for the alcohol group).

RESULTS

Alcohol intoxication impaired explicit recall of all cue types but did not impair implicit repetition priming. Emotionally negative and positive cues were more often recalled compared with neutral cues across all beverage groups, and emotionally negative cues demonstrated more priming than emotionally positive or neutral cues in all beverage groups.

CONCLUSIONS

Alcohol intoxication disrupted effortful recall of all cues, although the relative memory advantage of emotionally valenced over-neutral stimuli remained even after drinking. The effects of alcohol on unintentional memory priming were not statistically significant, but the effects of emotionally negative cues were. Further research is needed to better understand alcohol intoxication and emotional valence effects on memory processes during implicit memory tasks and the possibility that negative mood facilitates memory priming of negative emotional stimuli.

Psychoactive drugs and false memory: comparison of dextroamphetamine and δ-9-tetrahydrocannabinol on false recognition

RATIONALE

Several psychoactive drugs are known to influence episodic memory. However, these drugs' effects on false memory, or the tendency to incorrectly remember nonstudied information, remain poorly understood.

OBJECTIVES

Here, we examined the effects of two commonly used psychoactive drugs, one with memory-enhancing properties (dextroamphetamine; AMP), and another with memory-impairing properties (Δ(9)-tetrahydrocannabinol; THC), on false memory using the Deese/Roediger-McDermott (DRM) illusion.

METHODS

Two parallel studies were conducted in which healthy volunteers received either AMP (0, 10, and 20 mg) or THC (0, 7.5, and 15 mg) in within-subjects, randomized, double-blind designs. Participants studied DRM word lists under the influence of the drugs, and their recognition memory for the studied words was tested 2 days later, under sober conditions.

RESULTS

As expected, AMP increased memory of studied words relative to placebo, and THC reduced memory of studied words. Although neither drug significantly affected false memory relative to placebo, AMP increased false memory relative to THC. Across participants, both drugs' effects on true memory were positively correlated with their effects on false memory.

CONCLUSIONS

Our results indicate that AMP and THC have opposing effects on true memory, and these effects appear to correspond to similar, albeit more subtle, effects on false memory. These findings are consistent with previous research using the DRM illusion and provide further evidence that psychoactive drugs can affect the encoding processes that ultimately result in the creation of false memories.

Event-Related Theta Power during Lexical-Semantic Retrieval and Decision Conflict is Modulated by Alcohol Intoxication: Anatomically Constrained MEG

Language processing is commonly characterized by an event-related increase in theta power (4-7 Hz) in scalp EEG. Oscillatory brain dynamics underlying alcohol's effects on language are poorly understood despite impairments on verbal tasks. To investigate how moderate alcohol intoxication modulates event-related theta activity during visual word processing, healthy social drinkers (N = 22, 11 females) participated in both alcohol (0.6 g/kg ethanol for men, 0.55 g/kg for women) and placebo conditions in a counterbalanced design. They performed a double-duty lexical decision task as they detected real words among non-words. An additional requirement to respond to all real words that also referred to animals induced response conflict. High density whole-head MEG signals and midline scalp EEG data were decomposed for each trial with Morlet wavelets. Each person's reconstructed cortical surface was used to constrain noise-normalized distributed minimum norm inverse solutions for theta frequencies. Alcohol intoxication increased reaction time and marginally affected accuracy. The overall spatio-temporal pattern is consistent with the left-lateralized fronto-temporal activation observed in language studies applying time-domain analysis. Event-related theta power was sensitive to the two functions manipulated by the task. First, theta estimated to the left-lateralized fronto-temporal areas reflected lexical-semantic retrieval, indicating that this measure is well suited for investigating the neural basis of language functions. While alcohol attenuated theta power overall, it was particularly deleterious to semantic retrieval since it reduced theta to real words but not pseudowords. Second, a highly overlapping prefrontal network comprising lateral prefrontal and anterior cingulate cortex was sensitive to decision conflict and was also affected by intoxication, in agreement with previous studies indicating that executive functions are especially vulnerable to alcohol intoxication.

The effects of energy drinks alone and with alcohol on neuropsychological functioning

OBJECTIVE

Caffeinated energy drinks-alone or with alcohol-are heavily marketed to young adults, many of whom believe that caffeine counteracts some negative effects of alcohol intoxication. While the effects of caffeine and alcohol have been widely investigated, few studies have examined neuropsychological performance after consumption of a beverage containing both ingredients.

METHODS

In a double-blind, placebo-controlled design, 27 non-caffeine-deprived female participants were randomly assigned to consume a caffeinated energy drink alone, one containing alcohol, or a non-alcoholic, non-caffeinated control beverage. Pre- and post-test assessments were conducted using alternate forms of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).

RESULTS

Participants who consumed the energy drink plus alcohol evidenced significantly lower post-test performance on a global score of neuropsychological status. Specifically, deficits were found in both visuospatial/constructional and language performance scores. While participants who consumed the caffeinated beverage alone trended toward improved attention scores, neuropsychological status did not show meaningful changes from the pre- to post-test.

CONCLUSIONS

Consumption of an energy drink containing 6% alcohol by volume negatively influenced performance on a global measure of cognitive functioning.

False memory and obsessive-compulsive symptoms

BACKGROUND

The memory deficit hypothesis has been used to explain the maintenance of repetitive behavior in individuals with obsessive-compulsive disorder, yet the majority of studies focusing on verbal memory show mixed results. These studies primarily evaluated memory accuracy via the inclusion or omission of previously encountered material, as opposed to false recognition (i.e., the inclusion of erroneous material). We evaluated false memories and memory processes in individuals with obsessive-compulsive washing symptoms (OC), individuals matched on depression and anxiety without OC symptoms (D/A), and in nonanxious individuals (NAC).

METHODS

Twenty-eight OC, 28 D/A, and 29 NAC individuals read OC-threat relevant, positive, and neutral scenarios and then performed a recognition test. Erroneous recognition of words associated to encoded, but not previously viewed, scenarios were classified as false memories. To evaluate processes underlying memory, participants completed a modified remember/know task to examine whether the OC individuals differed from the other individuals in recollective clarity for false memories of OC-relevant (e.g., germs), positive (e.g., lottery), and neutral (e.g., bread) material.

RESULTS

The OC individuals used "know" more than the D/A and NAC individuals for false memories of threat. For veridical memories, the OC individuals used "know" more than the NAC, but not, D/A individuals.

CONCLUSIONS

The greater reliance on "know" (i.e., feelings of familiarity) in general and false threat memories in particular in individuals with OC symptoms may add to feelings of uncertainty for threat-relevant material, which may contribute to compulsive behavior.