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<td><span style="font-family:Helvetica, sans-serif; font-size:20px;font-weight:bold;">PsyPost – Psychology News Daily Digest (Unofficial)</span></td>
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<td><a href="https://www.psypost.org/a-single-dose-of-psilocybin-leads-to-long-lasting-optimism-boost-in-animal-study/" style="font-family:Helvetica, sans-serif; letter-spacing:-1px;margin:0;padding:0 0 2px;font-weight: bold;font-size: 19px;line-height: 20px;color:#222;">A single dose of psilocybin leads to long-lasting optimism boost in animal study</a>
<div style="font-family:Helvetica, sans-serif; text-align:left;color:#999;font-size:11px;font-weight:bold;line-height:15px;">Nov 22nd 2024, 08:00</div>
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<p><p>A recent study published in <em><a href="https://doi.org/10.1038/s41398-024-03103-7" target="_blank" rel="noopener">Translational Psychiatry </a></em>suggests that psilocybin, a compound found in certain psychedelic mushrooms, could increase optimism and engagement in tasks, offering potential insights into its benefits for treating depression. Using computational modeling, researchers demonstrated that rats given psilocybin showed a sustained increase in optimism, motivating them to engage more with their environment.</p>
<p>Depression is often characterized by withdrawal, pessimism, and a lack of motivation to engage with the world, making it difficult for affected individuals to benefit from rewarding experiences. Psilocybin has shown promise as a treatment for depression, but the specific mechanisms driving its therapeutic effects remain unclear. By using a controlled environment and animal models, the researchers aimed to uncover how psilocybin influences decision-making processes and optimism.</p>
<p>Understanding these processes could help refine treatments, ensuring they target the underlying mechanisms of depression. Unlike human trials, which can be influenced by participants’ expectations, studies on rats offer a way to examine pure pharmacological effects in a controlled setting.</p>
<p>“We were interested in the post-acute effects of psilocybin on the brain’s mechanisms. By understanding the mechanisms of psilocybin treatment, we can begin to determine who might benefit from psilocybin treatment for depression and who may not. Psychedelic therapies don’t work for everyone but are amazing for some; hopefully, understanding the mechanisms can help us learn why,” explained study author <a href="https://www.bethfisher.au/">Beth Fisher</a>, a PhD student at the Monash Centre for Consciousness and Contemplative Studies.</p>
<p>To explore the effects of psilocybin on optimism, the researchers used a combination of behavioral testing and computational modeling to identify changes in the rats’ decision-making processes. The sample included 22 female Sprague-Dawley rats, divided into two groups: one received a single dose of psilocybin, and the other was given a saline placebo.</p>
<p>The experiment centered on a reversal learning task, designed to measure the rats’ ability to adapt to changing reward contingencies. Each rat’s home cage was equipped with a device offering two nose-poke ports. Poking the correct port resulted in a reward (a sucrose pellet), while poking the incorrect port did not.</p>
<p>After 10 consecutive correct responses, the reward shifted to the opposite port, requiring the rats to adjust their behavior. The task was conducted for three hours daily over 14 consecutive days, allowing the rats to engage or remain inactive as they chose. The setup ensured that motivation and engagement could be assessed independently of other factors, such as hunger, since the rats had free access to standard food.</p>
<p>To better understand the cognitive processes underlying the rats’ behavior, the researchers applied computational models, including reinforcement learning and active inference models. These models evaluated decision-making parameters, such as optimism bias (how strongly the rats updated their beliefs after rewards versus losses) and loss aversion (the degree to which the rats avoided losses compared to seeking rewards).</p>
<p>The researchers found notable differences between the psilocybin-treated rats and the control group in both their behavior and underlying decision-making processes. Rats that received psilocybin displayed increased engagement with the reversal learning task, choosing to participate more frequently than the control group. This heightened engagement led to more rewards for the psilocybin group over time, particularly during the second week of testing. Despite engaging more, the psilocybin-treated rats also experienced more losses, suggesting they were less deterred by potential negative outcomes.</p>
<p>The computational modeling revealed two primary mechanisms driving this behavior. First, psilocybin-treated rats exhibited a stronger optimism bias, meaning they updated their expectations more after receiving rewards than after experiencing losses. This bias likely made the rats more inclined to anticipate positive outcomes, encouraging them to persist in the task. Second, psilocybin reduced the rats’ loss aversion, making them less sensitive to the negative impact of losses. This reduction in loss aversion helped sustain their motivation to engage with the task, even when they encountered setbacks.</p>
<p>“Our work found that psilocybin increased optimism over time in rats, which led to them engaging more with their environment,” Fisher told PsyPost. “Engaging with the world more can help people with depression who may be withdrawn.”</p>
<p>Interestingly, these effects became more pronounced over time. By the second week of testing, the psilocybin-treated rats consistently outperformed the control group in terms of task engagement and reward acquisition. This gradual increase in engagement aligns with previous research suggesting that psilocybin’s effects on brain plasticity and behavior may peak days or weeks after administration.</p>
<p>Importantly, the observed changes in engagement were not accompanied by increased general activity levels or reduced anxiety-like behaviors, indicating that the effects were specific to decision-making processes related to optimism and reward.</p>
<p>Although promising, the study has limitations. First, it was conducted in rats, and while animal models offer valuable insights, the findings may not directly translate to humans. Human decision-making is influenced by more complex factors, such as emotions and social contexts, which are difficult to replicate in animal studies.</p>
<p>“We would love to start translating this study to a human study! We would need to make adjustments to the time points and methods of collecting data after treatment, but this is all possible,” Fisher said. “Our work found that psilocybin increased optimism, but we are also working on other interventions that can increase optimism as well. The dream is to find a range of treatments that can help treat depression by increasing optimism and engagement with the world.”</p>
<p>The study, “<a href="https://www.nature.com/articles/s41398-024-03103-7" target="_blank" rel="noopener">Psilocybin increases optimistic engagement over time: computational modelling of behaviour in rats</a>,” was authored by Elizabeth L. Fisher, Ryan Smith, Kyna Conn, Andrew W. Corcoran, Laura K. Milton, Jakob Hohwy, and Claire J. Foldi.</p></p>
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<td><a href="https://www.psypost.org/neuroscientists-identify-a-reversible-biological-mechanism-behind-drug-induced-cognitive-deficits/" style="font-family:Helvetica, sans-serif; letter-spacing:-1px;margin:0;padding:0 0 2px;font-weight: bold;font-size: 19px;line-height: 20px;color:#222;">Neuroscientists identify a reversible biological mechanism behind drug-induced cognitive deficits</a>
<div style="font-family:Helvetica, sans-serif; text-align:left;color:#999;font-size:11px;font-weight:bold;line-height:15px;">Nov 22nd 2024, 06:00</div>
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<p><p>Researchers from the University of California, San Diego, have identified a shared mechanism in the brain that explains how different drugs, such as methamphetamine and PCP (commonly known as “angel dust”), result in similar cognitive impairments, including memory loss. The study, published in <a href="https://www.nature.com/articles/s41467-024-52451-x"><em>Nature Communications</em></a>, reveals that these drugs cause neurons in the medial prefrontal cortex to alter the way they communicate through a process called neurotransmitter switching.</p>
<p>The motivation for this research stemmed from a long-standing mystery in neuroscience: how do drugs with distinct mechanisms of action produce similar cognitive impairments? Methamphetamine influences dopamine signaling, while PCP targets glutamate systems.</p>
<p>Despite these differences, both drugs are known to impair memory and mimic symptoms of disorders like schizophrenia. By investigating a shared mechanism underlying these effects, the researchers hoped to uncover potential therapeutic targets for treating drug-induced cognitive deficits and other related conditions.</p>
<p>Cognitive impairments, including memory deficits, are common in individuals who misuse drugs. These impairments often persist long after the drug use has stopped, significantly impacting quality of life. Understanding the underlying neuronal mechanisms could not only help in treating these deficits but also shed light on broader neuropsychiatric conditions.</p>
<p>“Repeated consumption and misuse of addictive drugs can create a series of problems for both drug users and the society in which they live, such as lost work productivity and impaired relationships,” said study authors Marta Pratelli (an assistant project scientist) and Nicholas C. Spitzer (a professor in the neurobiology department).</p>
<p>“The effects of drugs on brain function—and, consequently, on user behavior—are not limited to the period of intoxication but can persist even after prolonged periods of abstinence. Long-lasting cognitive and memory deficits, for example, are prevalent among individuals that were repeatedly exposed to drugs or alcohol, but the underlying basis of these behavioral alterations is not well understood.”</p>
<p>“We were interested in exploring how drugs affect the brain, leading to long-lasting memory impairments. We asked whether a form of neuroplasticity called neurotransmitter switching, in which a group of neurons lose the transmitter they previously expressed and gain a new one, was involved.”</p>
<p>The researchers focused on the medial prefrontal cortex, a brain region essential for cognitive control and memory. Using mice as their model, they examined the effects of repeated exposure to methamphetamine and PCP. Both drugs were administered daily for 10 days, with a control group receiving no drugs.</p>
<p>The key finding was the discovery that both methamphetamine and PCP caused neurons in the medial prefrontal cortex to undergo neurotransmitter switching. Glutamatergic neurons began producing GABA and the same subset of neurons underwent this transformation after exposure to either drug.</p>
<p>“We were surprised that both drugs caused the transmitter switch in the same neurons,” Pratelli and Spitzer told PsyPost. “This unexpected result could explain why both drugs produce the same memory deficits.”</p>
<p>The researchers conducted behavioral tests to assess memory, such as the novel object recognition test and the spontaneous alternation task. Both tests evaluate the ability to remember and discriminate between new and familiar stimuli—a function closely tied to medial prefrontal cortex activity.</p>
<p>Mice exposed to either drug displayed significant deficits in these tasks, performing poorly compared to control animals. Importantly, the extent of the memory impairments correlated with the number of neurons that had switched from glutamate to GABA.</p>
<p>The researchers also explored the role of dopaminergic neurons in the ventral tegmental area — a small region in the midbrain that plays a key role in reward, motivation, and learning by producing and releasing dopamine to other parts of the brain. They found that increased activity in dopaminergic neurons in the ventral tegmental area was both necessary and sufficient to drive the neurotransmitter switching in the medial prefrontal cortex.</p>
<p>When these neurons were artificially stimulated using optogenetic techniques, glutamatergic neurons in the prefrontal cortex began producing GABA, even in the absence of drug administration. This experiment demonstrated that heightened dopaminergic activity alone could replicate the effects of methamphetamine and PCP.</p>
<p>“We were also surprised to find that artificially stimulating dopaminergic neurons in the ventral tegmental area, to mimic some of the effects of addictive substances, was sufficient to induce the same transmitter switching observed after treatment with methamphetamine or PCP, even in the absence of drug administration,” Pratelli and Spitzer said. “These findings suggest that drugs of abuse other than PCP and methamphetamine could cause the same transmitter switching by affecting the firing of dopaminergic neurons in the ventral tegmental area.”</p>
<p>One of the most exciting findings was the discovery that the neurotransmitter switch, and the associated memory deficits, are reversible. After the mice had undergone the neurotransmitter switch and exhibited memory impairments, interventions to normalize activity in the medial prefrontal cortex reversed both the neuronal and behavioral changes.</p>
<p>Clozapine, an antipsychotic drug known to reduce neural activity, was particularly effective. When administered after drug exposure, clozapine restored normal neurotransmitter production in the affected neurons and rescued memory function in the mice.</p>
<p>Similarly, targeted chemogenetic suppression of prefrontal cortex hyperactivity after the drug treatments reversed the neurotransmitter switch and behavioral deficits. These findings indicate that the memory impairments caused by methamphetamine and PCP are not permanent and can be mitigated with appropriate interventions.</p>
<p>“Repeated exposure to drugs of abuse changes the transmitter expressed by a group of cortical neurons, leading to long-lasting cognitive deficits,” Pratelli and Spitzer told PsyPost. “The good news is that this change in transmitter can be reversed, thereby normalizing behaviors.”</p>
<p>“Indeed, even after repeated exposure to PCP, it is possible to reverse the transmitter switch from glutamate to GABA and the resulting memory loss using clozapine, an antipsychotic drug. In addition, non-invasive methods for local reduction of brain activity, such as transcranial magnetic stimulation (TMS), could be developed to provide drug-free therapy for consumption of PCP or methamphetamine.”</p>
<p>While the findings are promising, the study has limitations. The experiments were conducted in mice, which may not fully replicate human drug use behaviors or brain complexity. “As with all research involving animal models, caution should be exercised in extrapolating the results to those that would be obtained with human subjects,” Pratelli and Spitzer noted. “For example, mice in this study did not self-administer drugs as humans would, and methamphetamine and PCP were administered to mice by the experimenter (once a day for 10 days).”</p>
<p>“Since there are many other drugs that increase electrical activity in the medial prefrontal cortex, and affect the firing of dopaminergic neurons in the ventral tegmental area, we want to find out whether some of them, such as the opiates, cause the same transmitter switch. We are also keen to learn whether non-invasive local suppression of drug-induced brain activity can be a general therapy for behavioral alterations caused by drug consumption. Finally, it would be interesting to investigate whether other instances of neurotransmitter switching are involved in drug-induced behaviors relevant to the development of substance use disorders.</p>
<p>“We are neuroscientists focused on achieving fundamental knowledge of the way in which the brain works and how the brain changes in response to experience,” the researchers added. “It is deeply satisfying to make discoveries that have the potential to produce therapies that would benefit people dealing with the consequences of drug consumption.”</p>
<p>The study, “<a href="https://doi.org/10.1038/s41467-024-52451-x" target="_blank" rel="noopener">Drug-induced change in transmitter identity is a shared mechanism generating cognitive deficits</a>,” was authored by Marta Pratelli, Anna M. Hakimi, Arth Thaker, Hyeonseok Jang, Hui-quan Li, Swetha K. Godavarthi, Byung Kook Lim, and Nicholas C. Spitzer.</p></p>
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<td><a href="https://www.psypost.org/can-daytime-sleepiness-predict-weight-gain-new-research-highlights-sex-differences/" style="font-family:Helvetica, sans-serif; letter-spacing:-1px;margin:0;padding:0 0 2px;font-weight: bold;font-size: 19px;line-height: 20px;color:#222;">Can daytime sleepiness predict weight gain? New research highlights sex differences</a>
<div style="font-family:Helvetica, sans-serif; text-align:left;color:#999;font-size:11px;font-weight:bold;line-height:15px;">Nov 21st 2024, 14:00</div>
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<p><p>New research published in <a href="https://www.sciencedirect.com/science/article/abs/pii/S2352721824000585"><em>Sleep Health</em></a> sheds light on how daytime sleepiness and body weight are interconnected over time, revealing key sex differences. The study found that men with higher levels of daytime sleepiness had consistently higher body mass index (BMI), while women who experienced increasing daytime sleepiness over time showed faster weight gain. Among women, this effect was most pronounced in younger participants.</p>
<p>Obesity is a significant public health challenge, increasing the risk of numerous chronic health conditions and premature mortality. Sleep disturbances, including daytime sleepiness, are often associated with obesity. While much research has focused on how obesity contributes to sleepiness—through mechanisms like sleep apnea—fewer studies have explored the reverse relationship: whether sleepiness itself can lead to weight gain.</p>
<p>This new study sought to fill this gap by examining how both levels and changes in daytime sleepiness influence BMI trajectories over time. Importantly, the researchers aimed to uncover potential differences between men and women, as previous studies suggest that obesity and sleep-related factors often differ by sex. By using longitudinal data and objective measures of sleepiness, the researchers hoped to gain deeper insights into the potential feedback loop between sleep health and weight gain.</p>
<p>The research utilized data from the Wisconsin Sleep Cohort Study, which began in 1988 and included a randomly selected sample of Wisconsin state employees aged 30 to 60. Participants underwent repeated sleep studies at roughly four-year intervals, contributing to a robust dataset spanning over two decades. For this study, data from 827 participants were analyzed, representing a total of 2,614 sleep study observations.</p>
<p>Daytime sleepiness was objectively measured using the Multiple Sleep Latency Test (MSLT), which records the time it takes for a person to fall asleep during controlled nap trials. Shorter sleep latencies indicate greater sleepiness. BMI was calculated at each visit based on height and weight measurements taken by trained technicians. The researchers also accounted for factors such as age, physical activity, stimulant use, and depressive symptoms.</p>
<p>The study revealed connections between daytime sleepiness and BMI trajectories, with distinct patterns for men and women. For men, higher levels of daytime sleepiness were consistently associated with higher BMI levels across the study period. This relationship suggests that men who are chronically sleepier during the day tend to maintain higher BMI levels compared to their less sleepy counterparts.</p>
<p>Interestingly, this association was observed at a between-person level, meaning that men with more significant daytime sleepiness generally had higher average BMI levels than other men. However, changes in sleepiness over time among men were not strongly linked to within-person changes in BMI. In other words, men who were consistently sleepier did not experience significant weight changes over time relative to themselves, even though they tended to have higher BMI levels overall compared to other men in the study.</p>
<p>For women, the findings were more dynamic. While baseline levels of sleepiness were not significantly associated with BMI, changes in sleepiness over time had a pronounced effect on BMI trajectories. Women who experienced increases in daytime sleepiness tended to gain weight more rapidly than those whose sleepiness levels remained stable or decreased. This relationship was particularly pronounced in younger women, indicating that age may play a role in how sleepiness impacts weight gain.</p>
<p>The stronger association in younger women could be influenced by hormonal changes, metabolic factors, or differences in activity levels compared to older women. These findings highlight the importance of monitoring sleep health as a potential factor in weight management for women, especially during early adulthood.</p>
<p>The researchers proposed several pathways through which daytime sleepiness might contribute to weight gain. Sleepiness may reduce physical activity, as individuals with low energy levels are less likely to engage in exercise or maintain an active lifestyle. Sleepiness has also been linked to changes in dietary preferences, such as increased cravings for high-fat or high-calorie foods, which can contribute to weight gain. Additionally, metabolic factors, including insulin resistance or altered energy regulation, may be influenced by chronic sleep deprivation or excessive daytime sleepiness.</p>
<p>Interestingly, the study did not find evidence that sleep apnea—the most common medical explanation for daytime sleepiness—was the primary mediator of these relationships. Although sleep apnea is a known contributor to both sleepiness and obesity, the findings suggested that the association between daytime sleepiness and BMI exists independently of sleep apnea severity. This independence underscores the broader impact of sleepiness on weight regulation, beyond its role as a symptom of specific sleep disorders.</p>
<p>While the study provides valuable insights, it is not without limitations. First, although daytime sleepiness and BMI were measured objectively, other factors like physical activity and dietary habits were self-reported, which could introduce bias. Additionally, the study sample was predominantly white and middle-aged, limiting the generalizability of the findings to more diverse populations.</p>
<p>The study, “<a href="https://doi.org/10.1016/j.sleh.2024.03.002">Objectively measured daytime sleepiness predicts weight change among adults: Findings from the Wisconsin Sleep Cohort Study</a>,” was authored by Yin Liu, Jodi H. Barnet, Erika W. Hagen, Paul E. Peppard, Emmanuel Mignot, and Eric N. Reither.</p></p>
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<td><a href="https://www.psypost.org/united-nations-hostage-simulation-reveals-how-biased-instructions-skew-eyewitness-identifications/" style="font-family:Helvetica, sans-serif; letter-spacing:-1px;margin:0;padding:0 0 2px;font-weight: bold;font-size: 19px;line-height: 20px;color:#222;">United Nations hostage simulation reveals how biased instructions skew eyewitness identifications</a>
<div style="font-family:Helvetica, sans-serif; text-align:left;color:#999;font-size:11px;font-weight:bold;line-height:15px;">Nov 21st 2024, 12:00</div>
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<p><p>A recent study published in the <em><a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/jip.1624" target="_blank" rel="noopener">Journal of Investigative Psychology and Offender Profiling</a></em> has revealed the impact of stress and biased instructions on eyewitness accuracy. Researchers found that participants who experienced a high-stress, simulated hostage scenario had low rates of correct identifications during lineup tasks conducted a week later. Biased instructions during the lineup further decreased overall accuracy, increasing the likelihood of choosing incorrectly. The findings underscore the challenges of eyewitness identifications in high-stress situations and the potential for flawed procedures to exacerbate errors.</p>
<p>Eyewitness testimony plays a significant role in criminal investigations, but it is also a leading cause of wrongful convictions. Despite extensive research on eyewitness accuracy, most studies have relied on controlled, artificial scenarios, such as videos or photos. These laboratory conditions often fail to replicate the heightened stress and complexity of real-world events, such as violent crimes. Stress, in particular, is thought to influence memory, with conflicting theories suggesting it could either impair or enhance recall, depending on the situation.</p>
<p>The new study sought to address this gap by using a more realistic and stressful setting: a simulated hostage scenario. The researchers aimed to examine how such conditions influence the accuracy of eyewitness identifications, as well as the effects of biased versus unbiased lineup instructions. By doing so, they hoped to provide insights that could help improve the reliability of eyewitness identifications in real-life cases.</p>
<p>“Eyewitness identification plays a crucial role in the criminal justice system, but it can be influenced by mistakes and biases,” said study author <a href="https://www.researchgate.net/profile/Thomas-Nyman" target="_blank" rel="noopener">Thomas J. Nyman</a>, a lecturer in forensic psychology at the University of Reading. “We wanted to explore how a simulated hostage situation, designed to replicate a highly stressful, violent, and threatening scenario, affects eyewitness identification accuracy.”</p>
<p>The researchers worked with 122 participants from an international criminal justice training program, conducted by the United Nations. “By working with the United Nations in Italy, we had a unique chance to conduct this research in a setting that closely mimics real-life situations, which is something traditional laboratory studies cannot do,” Nyman explained. “This collaboration gave us the opportunity to study eyewitness decision-making in ways that are not usually possible in standard academic research.”</p>
<p>Participants, who were from diverse backgrounds, underwent a high-stress, 45-minute hostage simulation. The scenario included mock insurgents armed with realistic weapons, physical intimidation, and a staged abduction. The setup aimed to replicate the chaotic and threatening conditions of a real-life violent crime.</p>
<p>One week after the event, participants completed multiple lineup tasks designed to identify the insurgents. Each lineup included three photos and was presented on a computer screen. Some lineups contained a photo of an actual perpetrator (“target present”), while others did not (“target absent”). To test the influence of bias, participants were randomly assigned to receive either biased or unbiased instructions.</p>
<p>Unbiased instructions informed participants that the perpetrator might not be in the lineup and encouraged them not to guess. In contrast, biased instructions implied that the perpetrator was present and urged participants to make an effort to choose someone, even if unsure.</p>
<p>During the task, the researchers recorded participants’ choices, their confidence in their decisions, and the time they took to respond. Altogether, the study analyzed 1,030 lineup decisions, providing a comprehensive dataset for understanding how stress and instruction type influenced accuracy.</p>
<p>For lineups with the perpetrator present, participants identified the correct individual only 38% of the time. For lineups where the perpetrator was absent, participants correctly rejected the lineup 54% of the time.</p>
<p>“We were surprised by the level of accuracy participants achieved despite the challenges,” Nyman told PsyPost. “That does not mean that accuracy was high, but the study involved high stress, multiple perpetrators, and a one-week delay between the event and the line-up. These factors are typically expected to lower accuracy substantially.”</p>
<p>Biased instructions had a significant impact, decreasing overall accuracy by promoting more guessing and incorrect choices. When biased instructions were used, participants were more likely to make a selection in both target-present and target-absent lineups. This increased the hit rate (correctly identifying a perpetrator when present) but also significantly raised the false alarm rate (incorrectly identifying someone in target-absent lineups). Specifically, false alarms were twice as common under biased instructions compared to unbiased ones.</p>
<p>The study also found a link between confidence and accuracy. Participants who expressed high confidence in their choices were more likely to be correct, particularly when unbiased instructions were given. However, biased instructions inflated confidence in incorrect choices, weakening the relationship between confidence and accuracy.</p>
<p>Response times provided additional insights. Participants who quickly rejected target-absent lineups were more likely to be correct. However, response time did not reliably predict accuracy in target-present lineups, suggesting that confidence and decision-making processes differ depending on the type of lineup.</p>
<p>“Our study shows that how a line-up is presented affects accuracy,” Nyman explained. “Biased instructions can help catch the guilty person but also increase the risk of mistakes, while unbiased instructions reduce errors but may miss the guilty person. Conducted in one of the most realistic hostage simulations to date, our findings are directly applicable to real-world settings, showing that biased line-up instructions lead to decreased accuracy.”</p>
<p>While the study provides valuable insights, it also has limitations. The use of a three-person lineup differs from the six- or eight-person lineups commonly used in real investigations, potentially inflating accuracy rates. Additionally, the researchers could not control for all variables that might influence identification, such as lighting conditions or the “weapon focus effect,” where attention is drawn to a weapon rather than the perpetrator’s face.</p>
<p>“While the realism of our study is a major strength, it also introduced challenges, such as the smaller line-up size and no control group,” Nyman noted. “Additionally, we could not isolate the effects of stress and multiple perpetrators. However, our findings align with existing research, suggesting these limitations did not undermine the core insights.”</p>
<p>The researchers recommend further studies to address these limitations and to explore other factors affecting eyewitness accuracy, such as race and cultural biases, varying levels of stress, and lineup procedures. They also emphasize the need for more ecologically valid research to better understand how real-world conditions impact memory and identification.</p>
<p>“Our long-term goal is to understand the factors that affect a person’s memory in real-life situations, such as stress, visual distance, lighting, and own-race bias,” Nyman said. “By examining how these factors impact eyewitness accuracy, we aim to help the justice system improve how eyewitness identifications are conducted and interpreted.”</p>
<p>“This study represents a rare intersection of academic research and international collaboration. Partnering with the United Nations and the Italian Army allowed us to conduct the most realistic investigation to date of eyewitness identification accuracy following a simulated hostile event. These insights are invaluable for informing practices that could help mitigate injustice worldwide.”</p>
<p>The study, “<a href="https://doi.org/10.1002/jip.1624" target="_blank" rel="noopener">Eyewitness identifications based on biased or unbiased line-up instructions after a realistic and violent hostage simulation</a>,” was authored by Thomas J. Nyman, Giulia Cappa, Angelo Zappalà, and Pekka Santtila.</p></p>
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<td><a href="https://www.psypost.org/beliefs-about-demographic-replacement-strongly-linked-to-support-for-political-violence/" style="font-family:Helvetica, sans-serif; letter-spacing:-1px;margin:0;padding:0 0 2px;font-weight: bold;font-size: 19px;line-height: 20px;color:#222;">Beliefs about demographic “replacement” strongly linked to support for political violence</a>
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<p><p>A recent study published in <em><a href="https://www.sciencedirect.com/science/article/pii/S2211335524002663" target="_blank" rel="noopener">Preventive Medicine Reports</a></em> sheds light on how certain beliefs and societal perceptions can influence support for political violence among white Americans. The research identifies a connection between “replacement thinking”—the belief that immigrants are displacing native-born white Americans—markers of social status threat, and endorsement of political violence. The findings suggest that these beliefs may increase the likelihood of individuals justifying violent actions to protect perceived social and cultural dominance.</p>
<p>Political violence is a growing concern in the United States, with incidents occurring at levels unseen in decades. Such violence not only disrupts political systems but also harms communities, creating long-lasting emotional and social impacts. The researchers sought to better understand the motivations behind support for political violence, particularly among white Americans. They focused on how the perception of diminishing white privilege and feelings of social or economic disadvantage might influence such attitudes.</p>
<p>The study centers on <a href="https://www.psypost.org/belief-in-white-replacement-conspiracy-linked-to-anti-social-traits-and-violence-risk/">the concept of “replacement thinking,”</a> which refers to the belief that demographic changes threaten the cultural and societal dominance of white Americans. This belief has been associated with high-profile violent incidents, such as the 2022 mass shooting in Buffalo, New York. The researchers hypothesized that individuals experiencing status threat—economic or social insecurity—might be more susceptible to these beliefs and, in turn, more likely to support political violence.</p>
<p>“I was interested in this topic because I wanted to know the motivators as to why people would want to commit political violence in the United States. Specifically, I was curious to what the motivators were for the insurrections who stormed the capital on January 6th,” said study author Paul. M Reeping, who conducted the research while a postdoctoral fellow at University of California, Davis.</p>
<p>The researchers analyzed data from the 2022 Life in America Survey, a nationally representative online survey conducted in English and Spanish between May and June 2022. The study focused on 5,976 non-Hispanic white participants. Participants were asked about their agreement with statements related to replacement thinking, their demographic and socioeconomic characteristics, and their support for political violence in various scenarios.</p>
<p>Replacement thinking was assessed by participants’ agreement with the statement, “In America, native-born white people are being replaced by immigrants,” with strong agreement categorized as endorsing this belief. Markers of status threat were identified through indicators such as relatively low income (household income at least one standard deviation below the median for their census tract), lack of a high school diploma, and racial composition of the respondents’ neighborhoods. Neighborhoods were classified as predominantly white (91–100% white), predominantly non-white (0–10% white), or racially diverse (11–90% white).</p>
<p>To measure support for political violence, participants were asked whether violence was justified in specific scenarios, including to preserve the “American way of life,” stop illegal immigration, and stop people who do not share the same beliefs from voting. Responses endorsing violence in any scenario were classified as support for political violence.</p>
<p>The analysis revealed significant relationships between replacement thinking, status threat, and support for political violence. Strong agreement with replacement thinking was associated with more than double the likelihood of endorsing political violence compared to those who did not hold this belief. This link persisted even when researchers adjusted for demographic factors, underscoring the powerful role of replacement thinking in shaping attitudes toward violence.</p>
<p>“I was not expecting that the belief in replacement thinking would have such a large magnitude on endorsement of political violence,” Reeping told PsyPost.</p>
<p>Markers of status threat also independently contributed to violence endorsement. For instance, respondents with relatively low income were 24% more likely to support political violence, even in the absence of replacement thinking. Similarly, those without a high school diploma were 29% more likely to justify violence.</p>
<p>The study also highlighted the influence of neighborhood racial composition on attitudes toward political violence. A U-shaped relationship emerged, with white respondents in predominantly white (91–100%) or predominantly non-white (0–10%) neighborhoods more likely to support political violence than those in racially diverse areas. This finding suggests that neighborhood diversity may mitigate feelings of threat and hostility.</p>
<p>Respondents living in more diverse neighborhoods (11–90% white) were the least likely to endorse political violence, aligning with theories of intergroup contact, which propose that exposure to diverse groups can reduce prejudice and stereotyping. The U-shaped pattern further indicates that both extreme homogeneity and perceived minority status can exacerbate perceptions of threat, fueling support for violence.</p>
<p>An interaction between replacement thinking and economic status provided additional insight into how these factors interact. While replacement thinking increased the likelihood of endorsing political violence, respondents with both replacement thinking and relatively low income showed a slightly reduced association compared to those with replacement thinking alone. This suggests some overlap in the mechanisms through which economic insecurity and replacement thinking influence attitudes, potentially moderating their combined effect.</p>
<p>“I was not expecting that there would be a U-shaped curve in endorsement of political violence by racial composition of census tract,” Reeping said. “In other words, white people who lived in census tracts that were 90%+ white, <em>and</em> those who live in census tracts that were 90% non-white, where most likely to endorse political violence. White individuals who lived in a census tract that was 60% non-white were the least likely to endorse political violence.</p>
<p>The study also revealed gender differences. Men with relatively low income were more likely to endorse political violence, while this association was not observed among women. Conversely, women living in predominantly non-white neighborhoods were more likely to support political violence, whereas this pattern was absent for men. These differences highlight the nuanced ways in which gender shapes the relationship between perceived threats and attitudes toward violence, suggesting that men and women may respond differently to similar social and economic pressures.</p>
<p>The study’s findings highlight that “diversity is generally a good thing: people who live in more diverse neighborhoods are less likely to endorse political violence than those who do not,” Reeping told PsyPost. “Additionally, when people feel left behind, especially compared to their peers, they are much more likely to endorse political violence—likely because they feel like the government is not working for them.”</p>
<p>The data is cross-sectional, meaning it provides a snapshot of attitudes at one point in time and cannot establish causation. While the study identifies strong associations between replacement thinking, status threat, and support for political violence, it cannot determine whether these beliefs directly lead to violent behaviors or whether other factors might influence both attitudes and beliefs.</p>
<p>“Just because someone endorses political violence, does not mean that they themselves will commit it,” Reeping noted.</p>
<p>To address these limitations, future research could adopt a longitudinal design to track changes in beliefs and attitudes over time. Such an approach would help clarify whether replacement thinking and status threat precede or result from shifts in political violence endorsements. Reeping hopes “to eventually get to a point where we can come up with some interventions to prevent political violence, especially in these tumultuous times.”</p>
<p>The study, “<a href="https://doi.org/10.1016/j.pmedr.2024.102851" target="_blank" rel="noopener">Replacement thinking, status threat, and the endorsement of political violence among non-Hispanic white individuals in the US: A cross-sectional study</a>,” was authored by Paul M. Reeping, Garen J. Wintemute, Sonia L. Robinson, Andrew Crawford, Elizabeth A. Tomsich, and Veronica A. Pear.</p></p>
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<p><strong>Forwarded by:<br />
Michael Reeder LCPC<br />
Baltimore, MD</strong></p>
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