Impact of Alcohol on Memory: A Systematic Review

Abstract

This reviews the literature in psychology on acute alcohol intoxication and memory. Special emphasis is placed on empirical studies that have systematically examined alcohol's effects on memory performance in forensic contexts. Three aspects of memory performance are considered, including memory accuracy (i.e., the ability of the complainant to accurately distinguish between correct and incorrect information about the crime), memory reliability (i.e., the probability that information recalled by the complainant at a given level of certainty is correct), and completeness (i.e., the quantity of information reported by the complainant). The results show that different memory performance measures are differentially important depending on whether we are policy makers formulating interview guidance, versus decision makers evaluating the strength of memory evidence in a given case. Overall, the research to date indicates that acute alcohol intoxication during rape affects the completeness but not the accuracy of what is remembered.

What does current science tell us about the accuracy, reliability, and completeness of intoxicated witnesses? A case example of the murder of a prime minister

“…This can, at least in part, be attributed to the use of different designs and alcohol doses, as well as to varying interview formats and timing (see also Jores et al, 2019 for a similar conclusion). However, decreased completeness and maintained accuracy has been rather consistent in studies that have used (a) an immediate interview, (b) alcohol doses generating BAC:s ∼0.06-0.10/∼0.6-0.8‰, and (c) a relatively open interview format (i.e., free recall or open questions) (e.g., Flowe et al, 2016Flowe et al, , 2021Karlen et al, 2017;Jores et al, 2019). Even though delaying the interview seems to reduce report completeness for both intoxicated and sober witnesses, intoxicated witnesses seem to be more negatively affected by this (i.e., report even less information in delayed interviews).…”

“…A dose of approximately 0.8g/kg (~0.8‰) has been shown sufficient to decrease episodic recall performance, in basic memory studies (Birnbaum et al, 1978 : 0.7g/100 ml, BAC = 0.08; Tracy and Bates, 1999 : 0.8ml/kg, BAC = 0.08) and in applied studies on alcohol intoxicated witnesses (e.g., Schreiber Compo et al, 2012 ; Flowe et al, 2016 ; Karlen et al, 2017 ). Within these cited studies, as in the review by Flowe et al ( 2021 ), it is important to note that the accuracy rate did not decrease at these BAC-levels.…”

“…In a systematic review of 19 empirical studies that had examined the impact of alcohol on memory in forensic contexts (Flowe et al, 2021), three crucial areas of memory performance were identified: memory accuracy (i.e., the ability of the witness to distinguish between correct and incorrect information pertaining to the crime); memory reliability (i.e., the credibility of the witness in terms of how safe it is to rely on their evidence); and completeness (i.e., the quantity of information provided). In line with a meta-analysis (Jores et al, 2019), the review by Flowe et al (2021) showed that acute alcohol intoxication (mean BAC-levels in most studies = 0.03-0.09) deleteriously affected the completeness of the information, but not its accuracy or the reliability of what had been remembered. This is hardly surprising since, despite such findings, the reliability of intoxicated witnesses' ability to perceive and recall events has long been questioned within the judicial system (Benton et al, 2006;Evans et al, 2009).…”

“…The degree of alcohol's impairment of cognitive functions is dose dependent, causing successively increasing negative effects on many cognitive functions, such as focused attention, divided attention, and working memory capacity (Sayette, 1993 ; Curran, 2006 ; Zoethout et al, 2011 ; Dry et al, 2012 ). In a systematic review of 19 empirical studies that had examined the impact of alcohol on memory in forensic contexts (Flowe et al, 2021 ), three crucial areas of memory performance were identified: memory accuracy (i.e., the ability of the witness to distinguish between correct and incorrect information pertaining to the crime); memory reliability (i.e., the credibility of the witness in terms of how safe it is to rely on their evidence); and completeness (i.e., the quantity of information provided). In line with a meta-analysis (Jores et al, 2019 ), the review by Flowe et al ( 2021 ) showed that acute alcohol intoxication (mean BAC-levels in most studies = 0.03–0.09) deleteriously affected the completeness of the information, but not its accuracy or the reliability of what had been remembered.…”

“…Based on the negative impact of alcohol on several cognitive functions crucial for encoding information (e.g., maintaining attention, organizing information), it should not be surprising that consuming alcohol before encoding an event often disrupts later recall, both in basic laboratory studies on memorizing lists of words and in applied forensic studies using interviews (Mintzer, 2007 ; Zoethout et al, 2011 ; Jores et al, 2019 ; Flowe et al, 2021 ). However, research overviews (e.g., White, 2003 ; Mintzer, 2007 ) have emphasized that BAC:s <0.15 generate only small to moderate impairing effects on memory.…”