Alcohol and false recognition: a dose-effect study

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.

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.

Effects of caffeine on alcohol reinforcement: beverage choice, self-administration, and subjective ratings

RATIONALE

Combining alcohol and caffeine is associated with increased alcohol consumption, but no prospective experimental studies have examined whether added caffeine increases alcohol consumption.

OBJECTIVES

This study examined how caffeine alters alcohol self-administration and subjective reinforcing effects in healthy adults.

METHODS

Thirty-one participants completed six double-blind alcohol self-administration sessions: three sessions with alcohol only (e.g., beverage A) and three sessions with alcohol and caffeine (e.g., beverage B). Participants chose which beverage to consume on a subsequent session (e.g., beverage A or B). The effects of caffeine on overall beverage choice, number of self-administered drinks, subjective ratings (e.g., Biphasic Alcohol Effects Scale), and psychomotor performance were examined.

RESULTS

A majority of participants (65%) chose to drink the alcohol beverage containing caffeine on their final self-administration session. Caffeine did not increase the number of self-administered drinks. Caffeine significantly increased stimulant effects, decreased sedative effects, and attenuated decreases in psychomotor performance attributable to alcohol. Relative to nonchoosers, caffeine choosers reported overall lower stimulant ratings and reported greater drinking behavior prior to the study.

CONCLUSIONS

Although caffeine did not increase the number of self-administered drinks, most participants chose the alcohol beverage containing caffeine. Given the differences in subjective ratings and pre-existing differences in self-reported alcohol consumption for caffeine choosers and nonchoosers, these data suggest that decreased stimulant effects of alcohol and heavier self-reported drinking may predict subsequent choice of combined caffeine and alcohol beverages. These predictors may identify individuals who would benefit from efforts to reduce risk behaviors associated with combining alcohol and caffeine.

The sensitivity of laboratory tests assessing driving related skills to dose-related impairment of alcohol: A literature review

Laboratory tests assessing driving related skills can be useful as initial screening tools to assess potential drug induced impairment as part of a standardized behavioural assessment. Unfortunately, consensus about which laboratory tests should be included to reliably assess drug induced impairment has not yet been reached. The aim of the present review was to evaluate the sensitivity of laboratory tests to the dose dependent effects of alcohol, as a benchmark, on performance parameters. In total, 179 experimental studies were included. Results show that a cued go/no-go task and a divided attention test with primary tracking and secondary visual search were consistently sensitive to the impairing effects at medium and high blood alcohol concentrations. Driving performance assessed in a simulator was less sensitive to the effects of alcohol as compared to naturalistic, on-the-road driving. In conclusion, replicating results of several potentially useful tests and their predictive validity of actual driving impairment should deserve further research. In addition, driving simulators should be validated and compared head to head to naturalistic driving in order to increase construct validity.

The effects of acute alcohol intoxication on the cognitive mechanisms underlying false facial recognition

RATIONALE

False face recognition rates are sometimes higher when faces are learned while under the influence of alcohol. Alcohol myopia theory (AMT) proposes that acute alcohol intoxication during face learning causes people to attend to only the most salient features of a face, impairing the encoding of less salient facial features. Yet, there is currently no direct evidence to support this claim.

OBJECTIVES

Our objective was to test whether acute alcohol intoxication impairs face learning by causing subjects to attend to a salient (i.e., distinctive) facial feature over other facial features, as per AMT.

METHODS

We employed a balanced placebo design (N = 100). Subjects in the alcohol group were dosed to achieve a blood alcohol concentration (BAC) of 0.06 %, whereas the no alcohol group consumed tonic water. Alcohol expectancy was controlled. Subjects studied faces with or without a distinctive feature (e.g., scar, piercing). An old-new recognition test followed. Some of the test faces were "old" (i.e., previously studied), and some were "new" (i.e., not previously studied). We varied whether the new test faces had a previously studied distinctive feature versus other familiar characteristics.

RESULTS

Intoxicated and sober recognition accuracy was comparable, but subjects in the alcohol group made more positive identifications overall compared to the no alcohol group.

CONCLUSIONS

The results are not in keeping with AMT. Rather, a more general cognitive mechanism appears to underlie false face recognition in intoxicated subjects. Specifically, acute alcohol intoxication during face learning results in more liberal choosing, perhaps because of an increased reliance on familiarity.

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.

Recognition Memory for High and Low Associative Stimuli in Autistic Individuals with Outstanding Memory Skill

BACKGROUND

Individuals with autism exhibit typical recognition memory performance, but they show a reduced use of context and relational processing in more complex memory tasks. It is unclear whether the same is true for autistic individuals with exceptional memory skill for whom superior rote memory skill has been assumed.

OBJECTIVE

In this study, we investigated recognition memory for high and low associative stimuli in autistic memory experts. In accord with the rote memory notion, we expected an equal recognition performance for high and low associative stimuli and superior memorizing of nonsense material compared to control participants.

METHOD

Seven autistic memory experts and seven typically developed control subjects, matched according to age, sex, handedness, and full-scale intelligence quotient (IQ), were examined on a continuous old-new recognition paradigm, including high or low associative pseudowords and shapes. Memory expertise was characterized as a currently present outstanding memory skill above the subject's general level of ability and above the general population and was validated through direct clinical observation or some form of credible evidence.

RESULTS

Our hypotheses were partially corroborated with autistic memory experts recognizing high and low associative shapes equally well in contrast to control participants who showed superior recognition of high associative shapes. However, memory experts did not outperform control participants in the recognition of low associative shapes. There were no differences for the recognition of pseudowords.

CONCLUSIONS

Findings do not indicate enhanced memory for nonsense material, but a failure to make use of semantic features of abstract stimuli as assumed for autism as a whole.

Alternative substance paradigm: effectiveness of beverage blinding and effects on acute alcohol responses

A fundamental goal of double-blind alcohol challenge studies is to reduce alcohol expectancies, though there is little research on the effectiveness of blinding procedures and their relationship to acute alcohol responses. This study examined social drinkers' perception of beverage content and related alcohol response during 3 separate double-blind experimental sessions with placebo, low-dose alcohol (0.4 g/kg), and high-dose alcohol (0.8 g/kg). Using the alternative substance paradigm, participants (N = 182) were informed that the beverage they consumed might contain alcohol, a stimulant, a sedative, or a placebo. At several time points, subjective and objective measures were obtained, and participants were asked to identify which substance they received. During both placebo and low-dose alcohol sessions, 33% and 50% of participants, respectively, did not correctly identify the beverage content; during the high-dose alcohol session, 20% did not correctly identify the beverage. Although correct and incorrect identifiers at any dose level did not differ on major background variables, drinking characteristics, or psychomotor performance during these sessions, they did differ on self-reported subjective responses, with greater sedation reported by incorrect identifiers in the placebo and high-dose conditions. In summary, results suggest that the alternative substance paradigm may be a viable option for alcohol laboratory studies, particularly for repeated sessions in within-subject designs and in cases in which the experimenter wants to reduce expectancy by not revealing a priori that alcohol is being administered.

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.

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

RATIONALE

Alcohol impairs explicit memory, whilst leaving implicit memory relatively intact. Less is known about its effects on false memories.

AIM

The present study examines the effects of alcohol on explicit and implicit false memories using study list repetition as a tool for modulating learning at encoding.

METHODS

Thirty-two participants were given either an alcohol (0.6 g/kg) or placebo beverage before undergoing an encoding phase consisting of 10 lists of nine associated words (veridical items). Each list was associated to a word, which was not presented at encoding (semantically associated non-studied lure; critical item), serving as the measure for false memory. Half of the lists were presented once, and half were repeated three times. The next day, participants underwent an implicit (stem completion and post hoc awareness measurements), and an explicit (free recall) task.

RESULTS

Alcohol decreased veridical and false explicit memory for singularly presented lists compared to placebo; no group difference existed for repeated lists. Implicit veridical memory was not affected by alcohol. Awareness memory measures demonstrated in placebo participants an increased ability with repetition in rejecting false memories. The reverse was found in intoxicated participants who with repetition accepted more false memories.

CONCLUSION

Alcohol appears to decrease semantic activation leading to a decline in false memories. Increased learning with repetition, which increases the rejection of false memories under placebo, is reversed under alcohol leading to a decrease in rejection of false memories. The latter effect of alcohol may be due to its ability to impair monitoring processes established at encoding.

Alcohol and triazolam: differential effects on memory, psychomotor performance and subjective ratings of effects

The effects of alcohol (0.80 g/kg) and the benzodiazepine hypnotic triazolam (0.25 mg/70 kg) were compared directly in a double-dummy, double-blind, placebo-controlled, repeated-measures design in 18 healthy volunteers. While alcohol (0.80 g/kg) and triazolam (0.25 mg/70 kg) produced comparable levels of psychomotor performance impairment, a dissociation was observed, such that the magnitude of memory impairment (measured by d', participants' sensitivity in discriminating between old and new words in the recognition memory paradigm) was greater with triazolam than with alcohol, whereas subjective ratings of the overall strength of drug effect were higher with alcohol than with triazolam. Participants also adopted a more conservative response bias in the recognition memory paradigm in the alcohol (0.80 g/kg) condition relative to both placebo and triazolam (0.25 mg/70 kg). In addition to characterizing the adverse effects of two widely used psychoactive substances, the present results may also contribute to the understanding of underlying neurochemical mechanisms.

Cognitive impairment in methadone maintenance patients

Few well-controlled studies have examined psychomotor and cognitive performance in methadone maintenance patients (MMP). In the present study, performance of 18 opioid-dependent MMP was evaluated relative to that of 21 control participants without substance abuse histories. The MMP and control groups were balanced with respect to gender, race, age, years of education, current employment status, current reading level, and estimated IQ score. Recent drug abstinence was verified by urine testing. Participants with a urine screen positive for benzodiazepines or a breathalyzer test positive for alcohol prior to performance testing were excluded. To avoid testing under conditions of acute heroin or cocaine intoxication, but without testing under conditions of acute withdrawal, participants with current use of heroin or cocaine were only required to abstain for 24 h prior to performance testing. MMP exhibited impairment relative to controls in psychomotor speed (digit symbol substitution and trail-making tests), working memory (two-back task), decision making (gambling task), and metamemory (confidence ratings on a recognition memory test); results also suggested possible impairment in inhibitory mechanisms (Stroop color-word paradigm). MMP did not exhibit impairment in time estimation, conceptual flexibility or long-term memory. The wide range of impaired functions is striking, and may have important implications for daily functioning in MMP. Further research is necessary to determine the clinical significance of the impairments in laboratory-based tests for daily performance in the natural environment, as well as to differentiate impairments due to acute methadone dosing, chronic methadone maintenance, chronic poly-drug abuse, and other factors.