Mayo normative studies: regression-based normative data for ages 30-91 years with a focus on the Boston Naming Test, Trail Making Test and Category Fluency.

OBJECTIVE: Normative neuropsychological data are essential for interpretation of test performance in the context of demographic factors. The Mayo Normative Studies (MNS) aim to provide updated normative data for neuropsychological measures administered in the Mayo Clinic Study of Aging (MCSA), a population-based study of aging that randomly samples residents of Olmsted County, Minnesota, from age- and sex-stratified groups. We examined demographic effects on neuropsychological measures and validated the regression-based norms in comparison to existing normative data developed in a similar sample. METHOD: The MNS includes cognitively unimpaired adults ≥30 years of age (n = 4,428) participating in the MCSA. Multivariable linear regressions were used to determine demographic effects on test performance. Regression-based normative formulas were developed by first converting raw scores to normalized scaled scores and then regressing on age, age2, sex, and education. Total and sex-stratified base rates of low scores (T < 40) were examined in an older adult validation sample and compared with Mayo's Older Americans Normative Studies (MOANS) norms. RESULTS: Independent linear regressions revealed variable patterns of linear and/or quadratic effects of age (r2 = 6-27% variance explained), sex (0-13%), and education (2-10%) across measures. MNS norms improved base rates of low performance in the older adult validation sample overall and in sex-specific patterns relative to MOANS. CONCLUSIONS: Our results demonstrate the need for updated norms that consider complex demographic associations on test performance and that specifically exclude participants with mild cognitive impairment from the normative sample.

Contingency inferences from base rates: A parsimonious strategy?

The pseudocontingency framework provides a parsimonious strategy for inferring the contingency between two variables by assessing the base rates. Frequently occurring levels are associated, as are rarely occurring levels. However, this strategy can lead to different contingency inferences in different contexts, depending on how the base rates vary across contexts. Here, we examine how base-rate consistency influences base-rate learning and reliance by contrasting consistent with inconsistent base rates. We hypothesized that base-rate learning is facilitated, and that people rely more on base rates if base rates are consistent. In Experiment 1, the base rates across four contexts implied the same (consistent) or different (inconsistent) contingencies. Base rates were learned equally accurately, and participants inferred contingencies that followed the base rates but deviated from the genuine contingencies within contexts, regardless of consistency. In Experiment 2, we additionally manipulated whether the context was a plausible moderator of the contingency. While we replicated the first experiment's results when the context was a plausible moderator, base-rate inferences were stronger for consistent base rates when the context was an implausible moderator. Possibly, when a moderation-by-context was implausible, participants also relied on the base-rate correlation across contexts, which implied the same contingency when base rates were consistent but was zero when the base rates were inconsistent. Thus, our findings suggest that contingency inferences from base rates involve top-down processes in which people decide how to use base-rate information.

d[Formula: see text]: Sensitivity at the optimal criterion location.

Signal detection theory (SDT) was developed to provide a measure of the discriminability of a signal against background noise, independently of response bias. However, equal discriminability over a range of bias is only achieved by the traditional signal detection measure d[Formula: see text] under a narrow set of conditions - i.e., binormal noise and signal distributions of equal variance and base rates. In response to observed departures from these conditions, more robust alternative measures of d[Formula: see text] have been developed, including da and, more recently, d[Formula: see text]. Each of these alternatives addresses some, but not all, of the difficulties that arise when the assumptions of SDT are violated. Moreover, none of these measures directly follow from a central idea of discriminability by an observer that adopts a minimize error count (MEC) strategy. I propose a new d[Formula: see text] alternative, d[Formula: see text], that is robust to violations of the standard signal detection assumptions, remains consistent with varying bias, and is grounded in the principle of discriminability following a MEC strategy. Simulations illustrate how d[Formula: see text] is similar to the recently developed d[Formula: see text] when the observer optimizes their criterion placement to minimize the number of errors but, unlike d[Formula: see text], remains consistent irrespective of the observer's criterion placement Moreover, unlike da, d[Formula: see text] reflects changes in discriminability related to base rates of signal vs. noise presentations. The use of d[Formula: see text] also has implications for the interpretation of bias metrics, such as ß and c, which are examined at the optimal criterion under a variety of conditions.

The Other Side of the Bell Curve: Multivariate Base Rates of High Scores on the Delis-Kaplan Executive Function System.

OBJECTIVE: Previous researchers have examined the frequency at which healthy participants obtain one or more low scores on neuropsychological test batteries, proposing five psychometric principles of multivariate base rates: (a) low scores are common, with their frequency contingent on (b) the low score cutoff used, (c) the number of tests administered/interpreted, and (d) the demographic characteristics and (e) intelligence of participants. The current study explored whether these principles applied to high scores as well, using the Delis-Kaplan Executive Function System (D-KEFS). METHOD: Multivariate base rates of high scores (≥75th, ≥84th, ≥91st, ≥95th, and ≥98th percentiles) were derived for a three-test, four-test, and full D-KEFS battery, using the adult portion of the normative sample (aged 16-89 years; N = 1050) stratified by education and intelligence. The full D-KEFS battery provides 16 total achievement scores (primary indicators of executive function). RESULTS: High scores occurred commonly for all batteries. For the three-test battery, 24.1% and 12.4% had 1 or more scores ≥95th percentile and ≥98th percentile, respectively. High scores occurred more often for longer batteries: 61.6%, 72.9%, and 87.8% obtained 1 or more scores ≥84th percentile for the three-test, four-test, and full batteries, respectively. The frequency of high scores increased with more education and higher intelligence. CONCLUSIONS: The principles of multivariate base rates also applied to high D-KEFS scores: high scores were common and contingent on the cutoff used, number of tests administered/interpreted, and education/intelligence of examinees. Base rates of high scores may help clinicians identify true cognitive strengths and detect cognitive deficits in high functioning people.

People Make the Same Bayesian Judgment They Criticize in Others.

When two individuals from different social groups exhibit identical behavior, egalitarian codes of conduct call for equal judgments of both individuals. However, this moral imperative is at odds with the statistical imperative to consider priors based on group membership. Insofar as these priors differ, Bayesian rationality calls for unequal judgments of both individuals. We show that participants criticized the morality and intellect of someone else who made a Bayesian judgment, shared less money with this person, and incurred financial costs to punish this person. However, participants made unequal judgments as a Bayesian statistician would, thereby rendering the same judgment that they found repugnant when offered by someone else. This inconsistency, which can be reconciled by differences in which base rate is attended to, suggests that participants use group membership in a way that reflects the savvy of a Bayesian and the disrepute of someone they consider to be a bigot.

The base rate principle and the fairness principle in social judgment.

Meet Jonathan and Elizabeth. One person is a doctor and the other is a nurse. Who is the doctor? When nothing else is known, the base rate principle favors Jonathan to be the doctor and the fairness principle favors both individuals equally. However, when individuating facts reveal who is actually the doctor, base rates and fairness become irrelevant, as the facts make the correct answer clear. In three experiments, explicit and implicit beliefs were measured before and after individuating facts were learned. These facts were either stereotypic (e.g., Jonathan is the doctor, Elizabeth is the nurse) or counterstereotypic (e.g., Elizabeth is the doctor, Jonathan is the nurse). Results showed that before individuating facts were learned, explicit beliefs followed the fairness principle, whereas implicit beliefs followed the base rate principle. After individuating facts were learned, explicit beliefs correctly aligned with stereotypic and counterstereotypic facts. Implicit beliefs, however, were immune to counterstereotypic facts and continued to follow the base rate principle. Having established the robustness and generality of these results, a fourth experiment verified that gender stereotypes played a causal role: when both individuals were male, explicit and implicit beliefs alike correctly converged with individuating facts. Taken together, these experiments demonstrate that explicit beliefs uphold fairness and incorporate obvious and relevant facts, but implicit beliefs uphold base rates and appear relatively impervious to counterstereotypic facts.

Population Base Rates and Disease Course of Common Psychiatric and Neurodegenerative Disorders.

Knowledge of population base rates of neurological and psychiatric disorders is fundamental for diagnostic decision making. Consideration of relevant probabilistic information can improve diagnostic efficiency and accuracy. However, such data continue to be misused or underutilized, which can lead to misdiagnoses and negative patient outcomes. The aim of the current review is to create an easily accessible and comprehensive reference of existing age of onset as well as prevalence and incidence data for common neurodegenerative and psychiatric disorders in adults. Relevant epidemiological data were compiled from well-respected and frequently-cited textbooks and scholarly studies. Reviews were collected from PubMed, and publicly-available sources were gathered from Google Scholar. Results are organized and presented in several tables and a figure, which can be used as a diagnostic guide for students and clinicians across healthcare disciplines.

On a problematic procedure to manipulate response biases in recognition experiments: the case of "implied" base rates.

The experimental manipulation of response biases in recognition-memory tests is an important means for testing recognition models and for estimating their parameters. The textbook manipulations for binary-response formats either vary the payoff scheme or the base rate of targets in the recognition test, with the latter being the more frequently applied procedure. However, some published studies reverted to implying different base rates by instruction rather than actually changing them. Aside from unnecessarily deceiving participants, this procedure may lead to cognitive conflicts that prompt response strategies unknown to the experimenter. To test our objection, implied base rates were compared to actual base rates in a recognition experiment followed by a post-experimental interview to assess participants' response strategies. The behavioural data show that recognition-memory performance was estimated to be lower in the implied base-rate condition. The interview data demonstrate that participants used various second-order response strategies that jeopardise the interpretability of the recognition data. We thus advice researchers against substituting actual base rates with implied base rates.

Univariate and Multivariate Base Rates of Score Elevations, Reliable Change, and Inter-Rater Discrepancies in the BRIEF-A Standardization Samples.

The Behavior Rating Inventory of Executive Function-Adult Version (BRIEF-A) is a standardized rating scale of subjective executive functioning. We provide univariate and multivariate base rates (BRs) for scale/index scores in the clinical range (T scores ≥65), reliable change, and inter-rater information not included in the Professional Manual. Participants were adults (ages = 18-90 years) from the BRIEF-A self-report (N = 1,050) and informant report (N = 1,200) standardization samples, as well as test-retest (n = 50 for self, n = 44 for informant) and inter-rater (n = 180) samples. Univariate BRs of elevated T scores were low (self-report = 3.3%-15.4%, informant report = 4.5%-16.3%). Multivariate BRs revealed the common occurrence of obtaining at least one elevated T-score across scales (self-report = 26.5%-37.3%, informant report = 22.7%-30.3%), whereas virtually none had elevated scores on all scales. Test-retest scores were highly correlated (self = .82-.94; informant = .91-.96). Inter-rater correlations ranged from .44 to .68. Significant (p < .05) test-retest T-score differences ranged from 7 to 12 for self-report, from 6 to 8 for informant report, and from 16 to 21 points for inter-rater T-score differences. Applications of these findings are discussed.

Fast optimism, slow realism? Causal evidence for a two-step model of future thinking.

Many researchers report that people have an optimistic bias when making predictions, but sometimes cautious realism is found. One resolution is that future thinking has two steps: The desired outcome is imagined first, followed by a sobering reflection on potential difficulty of getting there. Five experiments supported this two-step model (USA and Norway; N = 3213; 10,433 judgments), showing that intuitive predictions are more optimistic than reflective predictions. Participants were randomly assigned to rely on fast intuition under time-pressure or slow reflection after time-delay. In Experiment 1, participants in both conditions thought positive events were more likely to happen to them than to other people and that negative events were less likely, replicating the classic finding of "unrealistic optimism". Crucially, this optimistic tendency was significantly stronger in the intuitive condition. Participants in the intuitive condition also relied more on heuristic problem-solving (CRT). Experiments 2-3 found that participants in the intuitive condition thought they were at lower health risk than participants in the reflective condition. Experiment 4 provided a direct replication, with the additional finding that intuitive predictions were more optimistic only for oneself (and not about the average person). Experiment 5 failed to identify any intuitive difference in perceived reasons for success versus failure, but observed intuitive optimism in binary prediction of a future exercise habit. Experiment 5 also found suggestive evidence for a moderating role of social knowledge: Reflective predictions about oneself became more realistic than intuitive predictions only when the person's base-rate beliefs about other people were fairly accurate.

Base rates of non-credible performance in a post-secondary student sample seeking accessibility accommodations.

Objective: Performance Validity Tests (PVTs) have been used to identify non-credible performance in clinical, medicolegal, forensic, and, more recently, academic settings. The inclusion of PVTs when administering psychoeducational assessments is essential given that specific accommodation such as flexible deadlines and increased writing time can provide an external incentive for students without disabilities to feign symptoms. Method: The present study used archival data to establish base rates of non-credible performance in a sample of post-secondary students (n = 1045) who underwent a comprehensive psychoeducational evaluation for the purposes of obtaining academic accommodations. In accordance with current guidelines, non-credible performance was determined by failure on two or more freestanding or embedded PVTs. Results: 9.4% of participants failed at least two of the PVTs they were administered, of which 8.5% failed two PVTs, and approximately 1% failed three PVTs. Base rates of failure for specific PVTs ranged from 25% (b Test) to 11.2% (TOVA). Conclusions: The present study found a lower base rate of non-credible performance than previously observed in comparable populations. This likely reflects the utilization of conservative criteria in detecting non-credible performance to avoid false positives. By contrast, inconsistent base rates previously found in the literature may reflect inconsistent methodologies. These results further emphasize the importance of administering multiple PVTs during psychoeducational assessments. The implications of these findings can further inform clinicians administering assessments in academic settings and aid in the appropriate utilization of PVTs in psychoeducational evaluation to determine accessibility accommodations.

Base rates of low neuropsychological test scores in older adults with subjective cognitive impairment: Findings from a tertiary memory clinic.

Base rates of low scores are typically determined from normative samples, which differ from clinical samples. We examined base rates of spuriously low scores for 93 older adults with subjective cognitive impairment presenting to a memory clinic. Crawford's Monte Carlo simulation algorithm was used to estimate multivariate base rates by calculating the percentage of cognitively intact memory clinic patients who produced normed scores at or below the 5th percentile. Neuropsychological tests included: Weschler Adult Intelligence Scale block design, digit span backwards, coding, Weschler Memory Scale logical memory immediate/delayed; California Verbal Learning Test immediate/delayed memory; Brief Visuospatial Memory Test immediate/delayed; and Delis-Kaplan Executive Functioning category switching, letter number sequencing, and inhibition/switching. An estimated 33.58% of the cognitively intact memory clinic population would have one or more low scores, 14.7% two or more, 6.55% three or more, 2.94% four or more, and 1.31% 5 or more due to chance. Base rates were then applied to a subset of clinical data: all with dementia and most with MCI had low scores that exceeded the base rates. Determining base rates of spuriously low scores on a neuropsychological battery in clinical samples could reduce false positives by using empirical adjustments for expected low scores.

Multivariate Base Rates and Concussion Detection: A Comparative Study.

Recent research has yielded multivariate base rates (MBRs) of low scores in healthy populations using a widely adopted concussion screening measure, Immediate Postconcussion and Cognitive Testing (ImPACT). However, the extent to which individuals with concussion obtain reliable changes at divergent frequencies relative to healthy individuals is largely unknown. The present study examined whether MBRs of reliable change accurately discriminated between those with and without concussion. This archival review consisted of 129 healthy individuals and 81 individuals with concussion. MBRs of reliable change scores were examined at varying cutoffs and frequencies between those with and without concussion. Composites showed small to medium effect sizes in differentiating between those with and without concussion. MBRs of reliable change scores on ImPACT provided limited discriminative utility in isolation. Computations of posttest probabilities using Bayes' Theorem yielded evidence for incremental gains when utilizing MBRs of reliable change under certain constraints.

[Formula: see text]Enhanced interpretation of the BRIEF2: multivariate base rates of elevated scores in the standardization samples.

The Behavior Rating Inventory of Executive Function, Second Edition (BRIEF2) is a standardized rating (self, parent, and teacher) scale of executive functioning in children and adolescents. Here, we provide multivariate base rate (MBR) information (for the Self, Parent, and Teacher forms), which is not included in the BRIEF2 Professional Manual. Participants were children and adolescents for the BRIEF2 Self-Report (ages = 11-18; N = 803), Parent-Report (ages = 5-18; N = 1,400), and Teacher-Report (ages = 5-18; N = 1,400) standardization samples. We focused on cumulative (e.g., % of sample with oneor more elevated scores) MBRs across scales, which were examined at three elevation levels on each form: T≥ 60, ≥65, and ≥70. Across forms, MBRs predictably decreased with increasing number of elevated scores and at higher cutoffs. The cumulative MBR of having at least one score at T≥ 60 was common (37.5-42.2%), but less frequent at T≥ 70 (15.4-17.4%). The probability of having elevated scores on all scales was very low, irrespective of form, age, or elevation threshold (T≥ 60 = 2.4-4.4%; T≥ 65 = 1.0-1.4%; T≥ 70 = 0.0-0.7%). There was no clinically meaningful relation between demographic factors (age, gender, race, and parental education) and MBRs. These data provide clinicians and researchers with an enhanced way of concurrently interpreting multiple BRIEF2 scales.

Reasoning strategy vs cognitive capacity as predictors of individual differences in reasoning performance.

The dual strategy model posits that reasoners rely on two information processing strategies when making inferences: The statistical strategy generates a rapid probabilistic estimate based on associative access to a wide array of information, and the counterexample strategy uses a more focused representation allowing for a search for potential counterexamples. In this paper, we focused on individual differences in strategy use as a predictor of performance on four reasoning tasks: Belief bias, base rate neglect, conjunction fallacy, and denominator neglect. Predictions from the strategy use model were contrasted with predictions from Dual Process Theories, which suggest that individual differences in performance reflect variations in cognitive ability. In each of four studies, a large number (N ≈ 200) completed one of the above reasoning tasks, a strategy use diagnostic questionnaire, and measures of IQ, cognitive reflection, and numeracy. In three of four studies, individual differences in strategy use predicted differences in reasoning performance when the effects of the other variables were eliminated. Bayesian analysis indicated that none of the individual differences measures predicted a significant portion of variance on the conjunction fallacy task, and that strategy use was a strong predictor on the remaining three tasks. This research suggests that the type of strategy that is adopted paves a road to successful reasoning that is independent of cognitive capacity.

Cognitive Impairment in Late-Life Depression: A Comparative Study of Healthy Older People, Late-Life Depression, and Mild Alzheimer's Disease Using Multivariate Base Rates of Low Scores.

Late-Life Depression (LLD) is often associated with cognitive impairment. However, distinction between cognitive impairment due to LLD and those due to normal aging or mild Alzheimer's Disease (AD) remain difficult. The aim of this study was to present and compare the multivariate base rates of low scores in LLD, mild AD, and healthy control groups on a battery of neuropsychological tests. Participants (ages 60-89) were 352 older healthy adults, 390 patients with LLD, and 234 patients with mild AD (i.e., MMSE ≥ 20). Multivariate base rates of low scores (i.e., ≤ 5th percentile) were calculated for each participant group within different cognitive domains (verbal episodic memory, executive skills, mental processing speed, constructional praxis, and language/semantic memory). Obtaining at least one low score was relatively common in healthy older people controls (from 9.4 to 17.6%), and may thus result in a large number of false positives. By contrast, having at least two low scores was unusual (from 0.3 to 4.6%) and seems to be a more reliable criterion for identifying cognitive impairment in LLD. Having at least three low memory scores was poorly associated with LLD (5.9%) compared to mild AD (76.1%) and may provide a useful way to differentiate between these two conditions [ χ ( 1 ) 2 = 329.8, p < 0.001; Odds Ratio = 50.7, 95% CI = 38.2-77.5]. The multivariate base rate information about low scores in healthy older people and mild AD may help clinicians to identify cognitive impairments in LLD patients, improve the clinical decision-making, and target those who require regular cognitive and clinical follow-up.

Base Rates of Invalid Test Performance Across Clinical Non-forensic Contexts and Settings.

OBJECTIVE: Base rates of invalidity in forensic neuropsychological contexts are well explored and believed to approximate 40%, whereas base rates of invalidity across clinical non-forensic contexts are relatively less known. METHODS: Adult-focused neuropsychologists (n = 178) were surveyed regarding base rates of invalidity across various clinical non-forensic contexts and practice settings. Median values were calculated and compared across contexts and settings. RESULTS: The median estimated base rate of invalidity across clinical non-forensic evaluations was 15%. When examining specific clinical contexts and settings, base rate estimates varied from 5% to 50%. Patients with medically unexplained symptoms (50%), external incentives (25%-40%), and oppositional attitudes toward testing (37.5%) were reported to have the highest base rates of invalidity. Patients with psychiatric illness, patients evaluated for attention deficit hyperactivity disorder, and patients with a history of mild traumatic brain injury were also reported to invalidate testing at relatively high base rates (approximately 20%). Conversely, patients presenting for dementia evaluation and patients with none of the previously mentioned histories and for whom invalid testing was unanticipated were estimated to produce invalid testing in only 5% of cases. Regarding practice setting, Veterans Affairs providers reported base rates of invalidity to be nearly twice that of any other clinical settings. CONCLUSIONS: Non-forensic clinical patients presenting with medically unexplained symptoms, external incentives, or oppositional attitudes are reported to invalidate testing at base rates similar to that of forensic examinees. The impact of context-specific base rates on the clinical evaluation of invalidity is discussed.

When Success Is Not Enough: The Symptom Base-Rate Can Influence Judgments of Effectiveness of a Successful Treatment.

Patients' beliefs about the effectiveness of their treatments are key to the success of any intervention. However, since these beliefs are usually formed by sequentially accumulating evidence in the form of the covariation between the treatment use and the symptoms, it is not always easy to detect when a treatment is actually working. In Experiments 1 and 2, we presented participants with a contingency learning task in which a fictitious treatment was actually effective to reduce the symptoms of fictitious patients. However, the base-rate of the symptoms was manipulated so that, for half of participants, the symptoms were very frequent before the treatment, whereas for the rest of participants, the symptoms were less frequently observed. Although the treatment was equally effective in all cases according to the objective contingency between the treatment and healings, the participants' beliefs on the effectiveness of the treatment were influenced by the base-rate of the symptoms, so that those who observed frequent symptoms before the treatment tended to produce lower judgments of effectiveness. Experiment 3 showed that participants were probably basing their judgments on an estimate of effectiveness relative to the symptom base-rate, rather than on contingency in absolute terms. Data, materials, and R scripts to reproduce the figures are publicly available at the Open Science Framework: https://osf.io/emzbj/.

Brief iPad-Based Assessment of Cognitive Functioning with ImPACT® Quick Test: Prevalence of Low Scores Using Multivariate Base Rates.

OBJECTIVE: The ImPACT® Quick Test is a brief iPad-based battery of neurocognitive tests that has been standardized on a sample of children, adolescents, and adults (ages 12-70). This study provides information on the prevalence of ImPACT® Quick Test scores falling below specific percentiles in the normative sample to aid in clinical interpretation and reduce the risk of over-interpreting, or misinterpreting, a single low score. METHOD: Participants were 683 individuals ranging in age from 12 to 70, who were assessed individually. The ImPACT® Quick Test includes five subtests, contributing to three factor scores: motor speed, memory, and attention tracker. The prevalence of low factor scores, stratified by age and sex, were calculated using multivariate base rates. RESULTS: In the total sample, obtaining 1 or more scores below the 25th percentile was common (base rate, BR = 47.2%), but obtaining 2 or more scores in this range was uncommon (BR = 15.3%). Similarly, obtaining 1 or more scores below the 16th percentile was common (BR = 31.4%), but obtaining two or more scores in this range was uncommon (BR = 6.9%). There were small differences in BRs between sexes and the number of low scores was fairly similar across the age groups. CONCLUSION: Results from this study parallel previous work illustrating that a substantial percentage of healthy individuals will obtain one or more low test scores when administered a brief battery of cognitive tests. Given that some healthy individuals will obtain a single score below expected cut-offs, clinicians should caution against overinterpreting a single low test score.

The Base Rate Study: Developing Base Rates for Risk Factors and Indicators for Engagement in Violent Extremism.

Improvements have been made in identifying the prevalence of risk factors/indicators for violent extremism. A consistent problem is the lack of base rates. How to develop base rates is of equal concern. This study has two aims: (i) compare two methods for developing base rates; the Unmatched Count Technique (UCT) and direct questioning, (ii) generate base rates in a general population sample and compare these to a sample of lone-actor terrorists (n = 125). We surveyed 2108 subjects from the general population. Participants were recruited from an online access panel and randomly assigned to one of three conditions; direct survey, control, or UCT. Survey items were based on a lone-actor terrorist codebook developed from the wider literature. Direct questioning was more suitable under our study conditions where UCT resulted in deflation effects. Comparing the base rates identified a number of significant differences: (i) lone-actor terrorists demonstrated propensity indicators related to a cognitive susceptibility, and a crime- and/or violence-supportive morality more often; the general sample demonstrated protective factors more often, (ii) lone-actor terrorists demonstrated situational indicators related to a crime- and/or violence-supportive morality more often, whereas the general sample experienced situational stressors more often, (iii) lone-actor terrorists demonstrated indicators related to exposure to extremism more often. Results suggest there are measurable differences in the prevalence of risk factors between lone-actor terrorists and the general population. However, no single factor "predicts" violent extremism. This bears implications for our understanding of the interrelation of risk and protective factors, and for the risk assessment of violent extremism.