Effects of task complexity and practice on performance during acute alcohol intoxication

Effects of acute alcohol administration on working memory: a systematic review and meta-analysis

RATIONALE

Alcohol-induced executive function deficits may underlie associations between alcohol, self-regulation, and hazardous behaviors. Studies examining the effects of alcohol administration on working memory, an important executive functioning component, have produced mixed findings. Acute alcohol effects on working memory remain unclear.

OBJECTIVES

We aimed to conduct a systematic review and meta-analysis on the effects of acute alcohol administration on working memory outcomes in studies of healthy adults.

METHODS

We performed a systematic search of PubMed, MEDLINE, and PsycINFO from inception to June 2021. Studies were included if they met criteria, including healthy participants and administration of quantified alcohol doses against comparative controls. Data extracted included primary working memory outcomes, alcohol doses, and study characteristics. Study quality was assessed using an established validity measure. Working memory task type, alcohol dose, control condition type, and sex/gender composition were explored as moderators using mixed-effects models and meta-regressions.

RESULTS

Thirty-two studies (1629 participants) provided sufficient data for 54 comparisons between alcohol and control conditions. Random-effects meta-analysis indicated that alcohol administration produced significant, small- to medium-sized working memory decrements (g [95% CI] =  - 0.300 [- 0.390 to - 0.211], p < 0.001). Moderation analyses suggested that these effects differed as a function of task type, dose, control condition type, and sex/gender composition. The average quality rating across studies was good.

CONCLUSIONS

Alcohol administration significantly impaired working memory performance, particularly when executive-related manipulation processes were involved. Future research is needed to investigate how alcohol-induced working memory impairments relate to compromised self-regulation, hazardous behavior, and negative drinking consequences.

Suicide Attempts: How Does the Acute Use of Alcohol Affect Suicide Intent?

BACKGROUND

Very few studies have specifically addressed the role of the acute use of alcohol (AUA) in suicide attempts.

OBJECTIVE

Our study compared the suicide intent scores of self-poisoning patients with and without AUA in order to examine the role of alcohol in attempted suicides.

METHODS

We recruited 516 patients admitted to the emergency department for self-poisoning. We screened blood alcohol concentrations (BACs) to determine whether these were positive or negative in the two groups. We collected data about covariates such as psychiatric disorders and sociodemographic and suicide characteristics. We then compared suicide intent between the groups, adjusted according to the covariates.

RESULTS

The patients with AUA had lower scores for suicide intent, but this factor only reduced the self-reporting score, with the scores for objective circumstances and risk similar between the groups. There was a correlation between BACs and self-reported suicide intentionality, but this was not significant.

CONCLUSION

Acute use of alcohol patients presented with lower suicide intent, as particularly explained by the self-report scores, but there were no differences between the groups in terms of risk and/or the objective circumstances. The role of alcohol in the self-reporting of suicide attempts must be addressed in future studies.

Alcohol effects on response inhibition: Variability across tasks and individuals

Considerable research has investigated the acute effects of alcohol on response inhibition, but a number of issues remain unresolved. Given that most studies use only a single laboratory task to assess inhibition, it is often difficult to determine whether alcohol's effects are task specific or generalize across measures of the same construct. Moreover, relatively few studies have directly compared effects of alcohol under ascending and descending blood alcohol concentrations (BACs), and those that have often failed to disentangle BAC limb effects from the effects of repeated testing. This study was intended to provide a test of alcohol's effects on behavioral inhibition using multiple laboratory measures in a relatively large sample and comparing effects under ascending and descending BAC. Young adults (N = 216) completed three commonly used inhibition tasks (Stroop, antisaccade, and stop-signal) at baseline and again 1-3 weeks later under one of three beverage conditions (alcohol, placebo or control) and one of two BAC limb conditions (ascending/descending or descending only). Findings indicated considerable specificity in alcohol's effects. Relative to control and placebo conditions, antisaccade performance suffered under both ascending and descending BAC and stop-signal reaction time (RT) suffered only under descending BAC. The Stroop RT interference effect was not affected by alcohol, though alcohol did impair response accuracy on incongruent Stroop trials. Baseline performance moderated effects of alcohol on both antisaccade accuracy and Stroop interference, suggesting the importance of individual differences. The current findings suggest that more specificity is required in characterizing acute effects of alcohol on inhibitory control. (PsycINFO Database Record

Effects of acute alcohol intoxication on executive functions controlling self-regulated behavior

Alcohol consumption may lead to deficits in the executive functions that govern self-regulation. These deficits could lead to risk-taking behaviors; therefore, it is important to determine the magnitude of these deficits on executive functioning. The purpose of this experiment was to investigate the acute effects of alcohol on three of the executive functions that are hypothesized to affect self-regulation, which are inhibition, set shifting, and working memory, using a mixed-methods study design. The participants were 75 moderate or heavy drinkers between the ages of 21 and 35 who were randomized into one of three beverage conditions (control, placebo, or 0.65-g alcohol dose/kg body weight). Performance on working memory, set shifting, and inhibition were measured pre- and post-beverage consumption. The results showed only a significant interaction in the working memory data, as there was an increase in performance post-beverage relative to pre-beverage for the control participants as compared to the alcohol and placebo participants. It was concluded that the dose of alcohol (BAC = 0.063%) given to moderate to heavy drinkers was not sufficient to cause significant impairment in the executive functions tested. The results were further discussed and methodological concerns were considered, such as the low BAC achieved, practice effects, and insensitivity of tasks.

Inhalation of Alcohol Vapor: Measurement and Implications

Decades of alcohol research have established the health risks and pharmacodynamic profile of oral alcohol consumption. Despite isolated periods of public health concern, comparatively less research has evaluated exposure to alcohol vapor. Inhaled alcohol initially bypasses first-pass metabolism and rapidly reaches the arterial circulation and the brain, suggesting that this route of administration may be associated with pharmacological effects that increase the risk of addiction. However, detailed reviews assessing the possible effects of inhaled alcohol in humans are lacking. A comprehensive, systematic literature review was conducted using Google Scholar and PubMed to examine manuscripts studying exposure to inhaled alcohol and measurement of biomarkers (biochemical or functional) associated with alcohol consumption in human participants. Twenty-one publications reported on alcohol inhalation. Fourteen studies examined inhalation of alcohol vapor associated with occupational exposure (e.g., hand sanitizer) in a variety of settings (e.g., naturalistic, laboratory). Six publications measured inhalation of alcohol in a controlled laboratory chamber, and 1 evaluated direct inhalation of an e-cigarette with ethanol-containing "e-liquid." Some studies have reported that inhalation of alcohol vapor results in measurable biomarkers of acute alcohol exposure, most notably ethyl glucuronide. Despite the lack of significantly elevated blood alcohol concentrations, the behavioral consequences and subjective effects associated with repeated use of devices capable of delivering alcohol vapor are yet to be determined. No studies have focused on vulnerable populations, such as adolescents or individuals with alcohol use disorder, who may be most at risk of problems associated with alcohol inhalation.

Acquisition of Conditioned Responses to a Novel Alcohol-Paired Cue in Social Drinkers

OBJECTIVE

This study examined the acquisition of conditioning between novel stimuli and single doses of alcohol in social drinkers. Environmental stimuli present during the consumption of alcohol or other drugs come to elicit conditioned responses that subsequently increase drug seeking. However, relatively few studies have examined the process of acquisition of these conditioned drug responses in human subjects.

METHOD

We used a procedure previously developed to study acquisition of conditioned responses to a methamphetamine-associated cue. In the present study we applied the paradigm to alcohol, pairing de novo neutral cues with alcohol in social drinkers (N = 36). We obtained measures of self-report, behavioral preference, emotional reactivity (assessed using facial electromyography), and attention to specific cues paired with administration of 0.6 g/kg 95% absolute alcohol or placebo.

RESULTS

After conditioning, participants showed an increase in attention toward the alcohol-paired cue, and this increase was associated with ratings of liking the alcohol-containing beverage during the conditioning sessions. In contrast to our previous findings with methamphetamine, the alcohol-paired cue did not elicit changes in emotional reactivity (measured by facial electromyography) or behavioral preference.

CONCLUSIONS

This study extends our previous findings with a stimulant drug to alcohol and highlights possible similarities and differences in conditioning with different classes of drugs. Conditioning with alcohol was less robust than with methamphetamine, but in both cases the conditioning that did occur was related to positive subjective drug response.

Inference Under the Influence: The Impact of Alcohol and Inhibition Conflict on Women's Sexual Decision Making

Integrating Zajonc's affective primacy framework with Steele and Southwick's Inhibitory Conflict Model, we hypothesized that alcohol would have its strongest impact when one's initial affective reaction was in direct conflict with more cognitively based inhibitory cues. In an alcohol by expectancy balanced placebo design, women viewed potential partners from a fictitious video dating service who varied in attractiveness and sexual risk. Only under high inhibitory conflict (i. e., an attractive, sexually risky partner) did alcohol enhance perceived relationship potential. Interestingly, women who consumed alcohol were not less likely to notice risk cues than their sober counter-parts. Alcohol expectancy resulted in both lower estimates of risk and elevated estimates of relationship potential for the high inhibitory conflict target. Thus, in situations involving high but not low inhibitory conflict, alcohol and alcohol expectancy may suppress the impact of inhibitory cues, enabling women to more readily pursue their initial affective reactions.

The effects of alcohol-containing e-cigarettes on young adult smokers

BACKGROUND

The liquids (e-liquids) used in an electronic cigarette (e-cigarette) contain myriad chemicals without adequate human inhalation safety data. Furthermore, the absence of e-liquid labeling requirements poses a formidable challenge to understanding how e-liquid constituents may promote nicotine addiction and/or have independent or synergistic biological effects when combined with nicotine. Ethyl alcohol is such a constituent, but has received little scientific interest in this context.

METHODS

Using a randomized, double blind, crossover design, acute changes in subjective drug effects, motor performance and biochemical measures of alcohol and nicotine intake were evaluated after directed and ad lib puffing from two commercially available e-liquids containing nicotine (8 mg/ml), vanilla flavor and either 23.5% (high) or 0.4% (trace) alcohol.

RESULTS

While no differences in subjective drug effects were observed between alcohol conditions, performance on the Purdue Pegboard Dexterity Test (PPDT) improved under the trace, but not under the 23.5% alcohol condition. Although plasma alcohol levels remained undetectable during testing, urine ethyl glucuronide (EtG), an alcohol metabolite, became measurable in three participants after puffing from the 23.5% alcohol e-cigarette.

CONCLUSIONS

Brief use of a widely available type of e-cigarette containing an e-liquid purchased from an internet vendor can negatively impact psychomotor performance and in some instances, produce detectable levels of a urine alcohol metabolite. Given the widespread and unregulated use of e-cigarettes, especially by youth and other vulnerable populations, further studies are needed to evaluate both the acute safety and long-term health risks of using alcohol-containing e-cigarettes.

Give me just a little more time: effects of alcohol on the failure and recovery of cognitive control

Numerous externalizing behaviors, from aggression to risk taking to drug abuse, stem from impaired cognitive control, including that brought about by the acute effects of alcohol. Although research generally indicates that alcohol impairs cognitive abilities, a close examination of the literature suggests that alcohol's effects are quite variable and likely depend on a number of contextual factors. The purpose of the current study was to characterize the effects of alcohol on cognitive control in terms of neural and behavioral responses to successful and unsuccessful control attempts. Participants were randomly assigned to consume an alcohol (0.80 g/kg ETOH), placebo, or nonalcoholic control beverage prior to completing a cognitive control (flanker) task while event-related brain potentials were recorded. Alcohol reduced the amplitude of the error-related negativity on error trials and increased the posterror compatibility effect in response time. Of particular interest, neural indices of conflict monitoring and performance adjustment (frontal slow wave) were attenuated by alcohol, but only on trials following errors. These functions had recovered, however, by 2 trials after an error. These findings suggest that alcohol's effects on cognitive control are best characterized as impaired (or delayed) recovery following control failures. Implications of these findings for understanding alcohol's effects on behavioral undercontrol are discussed.

Alcohol use across the lifespan: An analysis of adolescent and aged rodents and humans

Adolescence and old age are unique periods of the lifespan characterized by differential sensitivity to the effects of alcohol. Adolescents and the elderly appear to be more vulnerable to many of alcohol's physiological and behavioral effects compared to adults. The current review explores the differential effects of acute alcohol, predominantly in terms of motor function and cognition, in adolescent and aged humans and rodents. Adolescents are less sensitive to the sedative-hypnotic, anxiolytic, and motor-impairing effects of acute alcohol, but research results are less consistent as it relates to alcohol's effects on cognition. Specifically, previous research has shown adolescents to be more, less, and similarly sensitive to alcohol-induced cognitive deficits compared to adults. These equivocal findings suggest that learning acquisition may be differentially affected by ethanol compared to memory, or that ethanol-induced cognitive deficits are task-dependent. Older rodents appear to be particularly vulnerable to the motor- and cognitive-impairing effects of acute alcohol relative to younger adults. Given that alcohol consumption and abuse is prevalent throughout the lifespan, it is important to recognize age-related differences in response to acute and long-term alcohol. Unfortunately, diagnostic measures and treatment options for alcohol dependence are rarely dedicated to adolescent and aging populations. As discussed, although much scientific advancement has been made regarding the differential effects of alcohol between adolescents and adults, research with the aged is underrepresented. Future researchers should be aware that adolescents and the aged are uniquely affected by alcohol and should continue to investigate alcohol's effects at different stages of maturation.

Alcohol and human performance

The present paper presents a comprehensive review of studies concerned with the effects of alcohol on human performance. It attempts to review the studies within the framework of the information processing model. The effects of alcohol on information processing and transmission rates, sensory and perceptual processes, motorcontrol processes, attentional processes, and cognitive processes are described and discussed. It is proposed that such a processes analysis of human performance is a useful vehicle to describe the specific effects of alcohol. From the review it is concluded that much of the evidence from simple task description is equivocal. However, when information load is increased, when the stimulus-response incompatibility increases, and when the number of competing information processes occur in 'parallel', then a strong, consistent and coherent pattern of performance deterioration is associated with alcohol consumption.

Effects of alcohol (BAC 0.5‰) and ecstasy (MDMA 100 mg) on simulated driving performance and traffic safety

RATIONAL

An increasing number of fatal road-accidents have been reported in which ecstasy was found in the blood of drivers. Although, ecstasy is frequently found to have been used in combination with alcohol, studies on the acute effects of ecstasy co-administered with alcohol on driving performance are relatively rare.

OBJECTIVE

The present study was designed to establish the extent of driver impairment as a consequence of ecstasy or combined ecstasy and alcohol use as compared to driving under the influence of 0.3‰, 0.5‰ and 0.8‰ alcohol. Furthermore, subjective performance was also assessed.

RESULTS

Alcohol and ecstasy mainly influenced automated driving performance such as lateral and speed control. However, small to no effects of the substances were found on more complex driving behaviour. Overall, variance within the different driving measures was high especially when participants were treated with 3.4-methylenedioxy-methamphetamine (MDMA) and alcohol. Furthermore, equivalence testing showed that combined use may lead to impaired driving for some, but not all, drivers. Participants rated their own performance to be slightly worse than normal in both studies. Since driving was actually seriously deteriorated, this was a falsely positive assessment of their condition.

CONCLUSIONS

The dissociation between subjective perceptions and objective performance decrements are important notions for traffic safety since this may affect a driver's judgement of whether or not it is safe to drive. For example, an intoxicated individual might decide to drive because the feelings of alertness caused by MDMA cloud the impairing effects of other drugs such as alcohol, thereby creating a potentially serious risk for traffic safety.

Effects of alcohol on tests of executive functioning in men and women: a dose response examination

Alcohol has been shown to affect performance on tasks associated with executive functioning. However, studies in this area have generally been limited to a single dose or gender or have used small sample sizes. The purpose of this study was to provide a more nuanced and systematic examination of alcohol's effects on commonly used tests of executive functioning at multiple dosages in both men and women. Research volunteers (91 women and 94 men) were randomly assigned to one of four drink conditions (alcohol doses associated with target blood alcohol concentrations of .000%, .050%, .075%, and .100%). Participants then completed three tasks comprising two domains of executive functioning: two set shifting tasks, the Trail Making Test and a computerized version of the Wisconsin Card Sorting Task, and a response inhibition task, the GoStop Impulsivity Paradigm. Impaired performance on set shifting tasks was found at the .100% and .075% dosages, but alcohol intoxication did not impair performance on the GoStop. No gender effects emerged. Thus, alcohol negatively affects set shifting at moderately high levels of intoxication in both men and women, likely attributable to alcohol's interference with prefrontal cortex function. Although it is well established that alcohol negatively affects response inhibition as measured by auditory stop-signal tasks, alcohol does not appear to exert a negative effect on response inhibition as measured by the GoStop, a visual stop-signal task.

Separating the effects of alcohol and expectancy on brain activation: an fMRI working memory study

The aim of this study was to use BOLD fMRI to evaluate the effect of alcohol intoxication on neuronal activation, when controlling for expectancy. Behavioural studies have shown that both alcohol intoxication and expectancy affect cognition, mood and behaviour. However, previous neuroimaging studies have not separated the effects of alcohol intoxication from the possible confounding effects of expectancy. Forty-five healthy male participants participated in the study. A balanced placebo design with four groups was used together with a working memory paradigm. Half of the participants consumed a soft-drink before the MR scanning session (half of them were correctly informed about the content of their drink, and half were incorrectly informed that they consumed an alcoholic beverage), and the other half consumed an alcoholic beverage before the MR scanning session (half of them were correctly informed about the content of their drink, and half were incorrectly informed that they consumed a soft-drink). A blood alcohol concentration (BAC) of 0.08% was used as the alcohol intoxication level. The most conspicuous result was that alcohol intoxication decreased neuronal activation especially in the dorsal anterior cingulate cortex (dACC) and in prefrontal areas, while expectancy increased neuronal activation in the same areas. This study shows that alcohol intoxication and expectancy have opposite effects on neuronal activation. The present results could have implications for pharmacological imaging studies.

Toward cost-benefit analysis of acute behavioral effects of toluene in humans

There is increasing interest in being able to express the consequences of exposure to potentially toxic compounds in monetary terms in order to evaluate potential cost-benefit relationships of controlling exposure. Behavioral effects of acute toluene exposure could be subjected to cost-benefit analysis if the effects of toluene were quantitatively compared to those of ethanol ingestion, which has been monetized for applied contexts. Behavioral effects of toluene and ethanol were quantified by meta-analysis of studies from the peer-reviewed literature describing their effects on choice reaction time (reaction time in a test requiring a subject to choose among two or more alternatives before responding). The internal doses of these compounds were estimated by a general physiological and toxicokinetic (GPAT) simulation from exposure parameters provided in the reports. The reported effects were converted to a common metric (proportion of baseline) and related to the estimated internal doses of toluene and ethanol, from which dose-effect equations were fitted. The estimated effect of toluene was compared to the estimated effect of ethanol on the same dependent variable by deriving a dose-equivalence equation (DEE) to express the dose of toluene as an equivalent dose of ethanol on the basis of equal effect magnitude. A nomogram was constructed by GPAT simulation to relate the environmental exposure concentration of toluene to the equivalent effect magnitude of a range of ethanol internal doses. Behavioral effects and their evaluation are determined by internal doses, which in turn are determined by a variety of variables. In addition to concentration and duration of exposure, which determine internal dose by pharmacokinetic processes, the activity level of exposed persons is a major factor. This analysis provides a continuous function of the consequences of toluene exposure expressed as ethanol-equivalent doses within confidence limits. The resulting function has the potential to estimate the monetary values of behavioral deficits caused by a range of exposures to toluene from existing monetized information on ethanol.

Qualitative similarities in cognitive impairment associated with 24 h of sustained wakefulness and a blood alcohol concentration of 0.05%

Previous studies that have quantified fatigue-related cognitive impairment as blood alcohol concentration (BAC) equivalents have been limited by two issues: the effect of practice on tests of cognition and, more importantly, the statistic used to quantify change in cognitive performance. The current study addressed these issues by adopting an ABACA design, which allowed for the adequate control of practice effects, and by using effect size metrics, which enabled direct comparisons to be made in performance impairments as a result of fatigue (i.e. sustained wakefulness of 24 h) and alcohol (i.e. BAC of 0.05%). Cognitive performance under the fatigue and alcohol conditions required the use of the CogState battery. It was demonstrated that fatigue caused greater impairment than alcohol on the speed of continuous attention and memory and learning, and on the accuracy of complex matching. Alcohol was more detrimental than fatigue only on the accuracy of memory and learning. Performances on the remaining tasks were the same for both the fatigue and alcohol conditions. These differences and similarities in performance impairment are discussed emphasizing the deleterious cognitive effects of relatively short periods of sustained wakefulness.

Alcohol and cognitive control: implications for regulation of behavior during response conflict

Alcohol intoxication often leads to dysregulated behavior in contexts characterized by conflict between prepotent response tendencies and incompatible alternative responses. Recent research has identified 2 components of an anterior executive attention system that are essential for adaptive behavior when response conflict exists. Event-related potential (ERP) measures of evaluative and regulative cognitive control were collected to determine if impaired executive attention was responsible for observed behavior deficits when intoxicated. Intoxicated participants displayed task performance deficits on incongruent color-naming trials relative to sober controls. Alcohol did not affect P3 magnitude/latency, indicating that timing and integrity of stimulus evaluation remained intact. In contrast, alcohol did reduce frontal components of ERP that index evaluative and regulative cognitive control processes.

Effects of 10 mg and 15 mg oral procyclidine on critical flicker fusion threshold and cardiac functioning in healthy human subjects

The critical flicker fusion threshold (CFFT) is thought to index alertness and cortical arousal. Sedative drugs reduce CFFT while psychostimulants increase it. Procyclidine is an anticholinergic that is used to control the extrapyramidal side-effects of antipsychotics in schizophrenia. This study examined the effects of clinically relevant doses of oral procyclidine administration on CFFT and heart rate in two separate experiments (Experiment 1, drug dose: 10 mg, n = 16; Experiment 2, drug dose: 15 mg, n = 12) involving healthy subjects using a double-blind, placebo-controlled, cross-over design. 10 mg procyclidine had no significant effect on CFFT, heart rate or self-ratings of mood, but the 15 mg dose significantly lowered CFFT at 1 h and 2 h after procyclidine administration, increased drowsiness ratings and produced a drop in heart rate. The effects observed in this study may have implications for treatment compliance of schizophrenic patients, choice of antipsychotics, prescribing to patients with heart disease and monitoring of cardiac function under treatment. Further investigations are required to quantify the effects of procyclidine on CFFT and cardiac function in patients with schizophrenia.

Alcohol and visual performance

1. The authors examined the effect of acute alcohol consumption on a set of visual tasks: visual short term memory, depth perception, and attention. 2. In a repeated measurement design, thirteen subjects performed the tasks once sober and once intoxicated with 0.8 g/kg body weight pure ethanol in orange juice (33% alcohol). Subjects underwent a neuropsychological (Benton test) and a psychophysical test (vernier discrimination) both assessing visual short term memory, the test d2 as a measure of attention and concentration, and a psychophysical depth perception task. 3. Subjects demonstrated significant alcohol-related impairments in depth perception and in visual short term memory as assessed by the vernier discrimination task. However, the neuropsychological Benton test and test d2 failed to reveal alcohol-related changes in performance-probably due to superimposed learning effects. Performance was neither correlated with blood alcohol levels (BAL) nor perceived intoxication. Even though the current BAL was known to the subjects, only half of them demonstrated a close correlation between BAL and perceived intoxication.

The use of dose equivalency as a risk assessment index in behavioral neurotoxicology

This article reports changes with graduated dosage of alcohol on a standardized set of cognitive and psychomotor performance tests and refers to the approach as dose equivalency. Subjects (N = 20) were tested until their performance was stable on 10 tests from a microcomputer test battery. After administration of sufficient alcohol to achieve .15 blood alcohol level (BAL), using breath as the independent variable, the descending branch of the BAL curve was followed by measuring performance at set levels of alcohol. A dose-response relationship was confirmed in all performance tests (p less than .01), and multiple regression was used to select performance subtests that maximally predicted alcohol level. Four subtests were combined into a linear composite that related well to alcohol levels above 0.05 BAL (shrunken R = .75), which was used in a power function to approximate the roughly linear relation above 0.05, as well as the clearly nonlinear function between 0.05 and zero. It is suggested that alcohol, a powerful central nervous system depressant, can be a useful metric in communicating risk in neurotoxicological research.

Effects of alcohol and extended practice on divided-attention performance

The effects of alcohol and extended practice on divided attention were investigated using a visual tracking task and an auditory detection task. Subjects performed the tasks with and without alcohol, under single-task (S) and dual-task (D) conditions, both before and after they had received extended practice under single-task conditions without alcohol. Tracking accuracy improved with practice and was impaired under divided-attention conditions but was not affected by alcohol. Speed of detection was impaired by alcohol, improved by practice, and impaired by divided attention. Extended practice did not reduce the influence of alcohol. The effects of both alcohol and practice on speed of detection were significantly greater under dual-task conditions than under single-task conditions. Analysis of detection-task reaction times in terms of relative divided-attention costs, (D-S)/S, showed no effect of alcohol, but a highly significant reduction in costs with extended practice. It is concluded that (1) alcohol and practice can have quantitatively, but not qualitatively, similar effects on speeded performance, and (2) the effect of alcohol is not influenced by the attentional requirements of the task.

Factors affecting the drinking driver

Although the relationship between alcohol and traffic safety has been the subject of numerous studies, much remains unknown about the mechanisms by which alcohol contributes to traffic accidents. A number of other factors, which are reviewed in this paper, also can contribute to car accidents. They may also interact with alcohol, perhaps in a complex manner. Therefore, multiple factors rather than one single factor may contribute to automobile accidents for those who drink and drive.

Effects of practice on marijuana-induced changes in reaction time

The effect of smoked marijuana on performance of complex reaction time (RT) tasks was studied in two groups receiving different amounts of practice. Group M-P had no undrugged practice on the task before performing during marijuana intoxication for four consecutive daily sessions. On the fifth test day they performed while non-intoxicated. Group P-M performed the task on four consecutive test days while non-intoxicated, then smoked marijuana on session 5. Significant RT slowing was found on session 1 for group M-P (performing during marijuana intoxication without prior practice). Performance of this group improved rapidly and by the end of session 2 was not different from undrugged performance. Group P-M (receiving four sessions of undrugged practice before marijuana intoxication) showed no RT slowing while intoxicated. Reaction time performance may involve two phases: an early, attention-demanding phase which is sensitive to drug effects and a later, "automatic", phase which results from practice and is more resistant to drug effects. Pulse rate, salivary flow and subjective responses were recorded before and after smoking. These physiological and subjective measures showed only slight reduction in the acute effects of the drug over the four days of repeated usage.

Betel quid and reaction time

Fifteen male Yapese students participated in an experiment to see if the betel quid (betel nut, piper leaf, and calcium hydroxide) has overt effects on simple reaction time latencies. The data indicate that the entire quid produces discernible behavioral effects that are manifested in a relatively short time period following quid ingestion. Reaction time latencies lengthened following quid ingestion during the first 20 reaction time trials or within an apparent initial 5 minute interval.