Tonic immobility behaviour does not differ between fire salamander larvae from ponds and streams.

Tonic immobility is an antipredator defence in which the prey animal remains motionless after physical contact with the predator, pretending to be dead. This behaviour has been observed among a variety of taxa but has received only little attention in amphibian larvae. During our field studies with fire salamander larvae, we observed that larvae from different habitats display tonic immobility after handling. In our study site, we find larvae in pond and stream habitats, that differ in several aspects such as their stress response and their risk-taking behaviour, likely caused by the very different habitat conditions. We measured the time that the tonic immobility behaviour was displayed but found no difference between larvae from the two habitat types. Likewise, we also found no correlation between the size of the larvae and the duration of displaying the behaviour. In conclusion, we found that fire salamander larvae show tonic immobility, but found no evidence that the different habitat conditions influence the tonic immobility behaviour.

The prevalence of feigning and concealment of Covid-19 infections in an international sample.

We asked 463 participants from 21 countries whether they had feigned and/or concealed having a coronavirus infection during the pandemic period. 384 respondents (83%) reported having experienced a coronavirus infection. They were, on average, younger and reported more chronic health issues than participants who said they had never been infected. 65 (14%) admitted to having feigned the infection. Prevalence doubled (28%) when asked if they knew anyone who had feigned a coronavirus infection. Main motives for feigning were to stay at home and to obtain sick leave. As to having concealed a coronavirus infection, 56 (12%) responded affirmatively, but when asked about others, the prevalence reached 51% (n = 210). The most common reasons for concealment were to avoid letting others know and to not miss an event. Thus, both feigning and concealing infections can occur on a nontrivial scale, directly affecting prevalence rates in studies that rely on self-reported data collected from social platforms.

An overview of malingering and deception in neuropsychiatric cases.

Forensic practitioners must shoulder special responsibilities when evaluating over-stated pathology (e.g., malingering) as well as simulated adjustment. Such determinations may modify or even override other clinical findings. As a result, practitioners must be alert to their own misassumptions that may unintentionally bias their conclusions about response styles. Detection strategies for malingering-based on unlikely or markedly amplified presentations-are highlighted in this article. Given page constraints, assessment methods for feigning are succinctly presented with their applications to administrative, civil, and criminal referrals.

Classification accuracy and resistance to coaching of the Spanish version of the Inventory of Problems-29 and the Inventory of Problems-Memory: A simulation study with mTBI patients.

Objective: The present study aims to evaluate the classification accuracy and resistance to coaching of the Inventory of Problems-29 (IOP-29) and the IOP-Memory (IOP-M) with a Spanish sample of patients diagnosed with mild traumatic brain injury (mTBI) and healthy participants instructed to feign. Method: Using a simulation design, 37 outpatients with mTBI (clinical control group) and 213 non-clinical instructed feigners under several coaching conditions completed the Spanish versions of the IOP-29, IOP-M, Structured Inventory of Malingered Symptomatology, and Rivermead Post Concussion Symptoms Questionnaire. Results: The IOP-29 discriminated well between clinical patients and instructed feigners, with an excellent classification accuracy for the recommended cutoff score (FDS ≥ .50; sensitivity = 87.10% for coached group and 89.09% for uncoached; specificity = 95.12%). The IOP-M also showed an excellent classification accuracy (cutoff ≤ 29; sensitivity = 87.27% for coached group and 93.55% for uncoached; specificity = 97.56%). Both instruments proved to be resistant to symptom information coaching and performance warnings. Conclusions: The results confirm that both of the IOP measures offer a similarly valid but different perspective compared to SIMS when assessing the credibility of symptoms of mTBI. The encouraging findings indicate that both tests are a valuable addition to the symptom validity practices of forensic professionals. Additional research in multiple contexts and with diverse conditions is warranted.

Drop dead! Female mate avoidance in an explosively breeding frog.

Males' and females' reproductive strategies may differ, potentially leading to sexual conflict. Increased efforts by males (harassment, forced copulation, intimidation) to gain access to females could even negatively affect female survival and thus lead to reproductive failure for both individuals. In anurans, a higher mortality risk of mating females has been reported in explosive breeding species. During these mating events, several males cling to a female, which are mostly unable to get rid of the unwanted males. This can lead to the female's death. From the literature, it seems that females of explosive breeding frogs have no means to reject unwanted males. Here we describe female mate avoidance behaviours in the European common frog. We observed three female avoidance behaviours, namely 'rotation', 'release call(s)' and tonic immobility (death feigning). These behaviours were significantly associated with smaller female body size, and smaller females were more successful in escaping amplexus. Tonic immobility as a tactic to avoid mating or male harassment has only been observed in a handful of species and only in one other amphibian. Our observations show that females in explosive breeding frogs may not be as passive and helpless as previously thought.

Observations on neurophysiological pattern and behavioural traits as death-feigning mechanism in Eucryptorrhynchus scrobiculatus (Coleoptera: Curculionidae).

In adaptation to surrounding environmental stimuli, most insects exhibit defense behaviour (death feigning) to improve survival rates in the wild. However, the underlying mechanism of death feigning remains largely unknown. Here, we tested the neurophysiological pattern and behavioural traits of the death-feigning mechanism in the forestry pest Eucryptorrhynchus scrobiculatus. Using neuroanatomy, LC-MS/MS target metabolomics detection technology and qRT-PCR, we investigated the effects of neurochemicals and metabolic pathways in experimental weevils. Excision and drug tests were conducted to verify the key regulatory body parts involved in regulating the central nervous system in death feigning. Our results reconstructed the death-feigning mechanism of E. scrobiculatus: when the effective stimuli point of arousal weevils received mechanical stimulation, the thoracoabdominal ganglion transmitted signals into the brain through the ventral nerve cord, and then the brain regulated dopamine (DA) and serotonin (5-HT) metabolic pathways, reducing the expression of dopamine (dar2) and octopamine (oar1, oab2) receptor genes, finally inducing death feigning. Our study suggests that the variation of neurotransmitters in the brain is an important indicator of the physiological response of death feigning, and the results provide ecological and theoretical information for future investigations to reveal key behaviour and target genes for pest control.

Why fake death? Environmental and genetic control of tonic immobility in larval lacewings (Neuroptera: Chrysopidae).

Tonic immobility is a passive antipredator strategy employed late in the predation sequence that may decrease individual mortality in prey animals. Here, we investigate how energetic state and genetic predisposition influence antipredator decision-making in green lacewing larvae, Chrysoperla plorabunda (Fitch), using simulated predatory encounters. We demonstrate that tonic immobility is a plastic response influenced by energetic resource limitation. Larvae exposed to 1 or 2 days of food deprivation initiate tonic immobility more often and with less physical provocation than individuals fed ad libitum. Recently molted individuals exposed to food deprivation, the individuals most energetically challenged, engage in tonic immobility at a higher rate than any other group. We also find that variation in antipredator strategy between individuals is partly the result of within-population genetic variation. We estimate the propensity to enter tonic immobility to have a broad-sense heritability of 0.502. Taken together our results suggest that larval lacewings under energetic stress are more likely to engage in tonic immobility. Yet, energetic state does not explain all within-population variation, as individuals can have a genetic predisposition for tonic immobility.

Detecting Attention Deficit Hyperactivity Disorder and its feigning using the Personality Assessment Inventory.

Attention Deficit Hyperactivity Disorder is a relatively common and often disabling disorder in adults. However, feigning ADHD symptomatology is both easy and potentially common. We explored the most effective strategies for A) identifying individuals who had been diagnosed with ADHD based on existing PAI symptom indicators, and B), discriminating between feigned and genuine ADHD symptoms using PAI negative distortion indicators. Our sample consisted of 463 college aged participants who had been diagnosed with ADHD (n = 60), were asked to feign ADHD (n = 71), and a control group (n = 333). Self-reported diagnosis and successful feigning were corroborated by the CAARS-S: E scale. We first compared two PAI-derived ADHD indicators to determine which best differentiated between our ADHD and Control groups. Next, we compared seven negative distortion indicators to determine which could best distinguish between real and feigned ADHD symptoms. Our results revealed that the PAI-ADHD scale was the most effective symptom indicator. Further, the Negative Distortion Scale (NDS) was the most effective for identifying feigners. When assessing ADHD based on the PAI, the PAI-ADHD scale appears promising as an indicator of symptomatology, while the NDS appears useful to rule-out feigning.

The forensic assessment of dissociation: Distinguishing real from the unreal.

Because a wide range of disorders incorporate dissociative symptoms, evaluators should be familiar with evidence-based approaches to evaluating dissociation claims in the clinical and forensic context. This article provides specific guidelines for practitioners when conducting a forensic assessment of individuals who report dissociative symptoms. We review the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition disorders that include dissociation as a symptom, highlight how to distinguish genuine versus atypical symptoms of dissociative identity disorder, and summarize strengths and weaknesses of structured assessments in the evaluation of dissociative claims.

First description of injury feigning behavior in Godlewski's buntings.

Nest defense behavior helps ground-nesting birds improve their breeding success. Among such behaviors, injury feigning behavior (IFB) is one of the better ways to attract predators and protect birds' nests. IFB is generally associated with shorebirds in general and plovers in particular, however, through field observation, it has been found this behavior is also exhibited in bunting species when they facing the risk of predation. We attempt to explore the detailed description of this behavior in buntings and the factors that affect this behavior. Based on video-recordings of the nest defense behavior by the ground-nesting bird Godlewski's bunting (Emberiza godlewskii) against nest invaders, we explored the characteristic of IFB and differences in nest defense behavior during their brooding seasons. The results showed that female buntings had a distinct IFB: the wings of buntings incited within 60°-90° of the body, ran and called rapidly, pretending to be injured and unable to fly. The nest stage had significant and extremely significant effects on IFB and movement distance (MD), respectively. And IFB was more likely to occur in brooding (34.62%) than incubation period (16.42%). This indicates that there are significant differences in the IFB of buntings at different breeding stages.

Ruling out feigned crime-related amnesia? A response to Acklin (2022).

In a recent paper, Acklin discussed a case of possible amnesia for a murder in terms of neurobiology, psychoanalysis, and personality assessment. Acklin accepted the defendant's claim of amnesia for the crime as genuine. The considerable literature that takes a skeptical view of crime-related amnesia was not cited, and the possibility of feigning or malingering was "ruled out" with a single sentence that does not withstand scrutiny. A review of the literature on feigned amnesia suggests that it may not be possible to rule out malingering even if the best available tools are used: There has been minimal investigation of most validity tests and estimates of base rates of feigned amnesia for a crime vary widely and make estimates of Negative Predictor Power highly unreliable. Although one cannot know from the information presented if Acklin's defendant legitimately experienced amnesia, feigning could not be ruled out using an interview and the test data cited by Acklin. I call for a moratorium on publication of further articles on crime specific amnesia that do not conscientiously examine other potential explanations and do not use current best practices for assessing negative response bias.

Feigning Adult ADHD on a Comprehensive Neuropsychological Test Battery: An Analogue Study.

The evaluation of performance validity is an essential part of any neuropsychological evaluation. Validity indicators embedded in routine neuropsychological tests offer a time-efficient option for sampling performance validity throughout the assessment while reducing vulnerability to coaching. By administering a comprehensive neuropsychological test battery to 57 adults with ADHD, 60 neurotypical controls, and 151 instructed simulators, we examined each test's utility in detecting noncredible performance. Cut-off scores were derived for all available outcome variables. Although all ensured at least 90% specificity in the ADHD Group, sensitivity differed significantly between tests, ranging from 0% to 64.9%. Tests of selective attention, vigilance, and inhibition were most useful in detecting the instructed simulation of adult ADHD, whereas figural fluency and task switching lacked sensitivity. Five or more test variables demonstrating results in the second to fourth percentile were rare among cases of genuine adult ADHD but identified approximately 58% of instructed simulators.

Comparing the Ability of MMPI-2 and MMPI-2-RF Validity Scales to Detect Feigning: A Meta-Analysis.

Several meta-analyses of the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) and Minnesota Multiphasic Personality Inventory-2 Restructured Form (MMPI-2-RF) have examined these instruments' ability to detect symptom exaggeration or feigning. However, limited research has directly compared whether the scales across these two instruments are equally effective. This study used a moderated meta-analysis to compare 109 MMPI-2 and 41 MMPI-2-RF feigning studies, 83 (56.46%) of which were not included in previous meta-analyses. Although there were differences between the two test versions, with most MMPI-2 validity scales generating larger effect sizes than the corresponding MMPI-2-RF scales, these differences were not significant after controlling for study design and type of symptoms being feigned. Additional analyses showed that the F and Fp-r scales generated the largest effect sizes in identifying feigned psychiatric symptoms, while the FBS and RBS were better at detecting exaggerated medical symptoms. The findings indicate that the MMPI-2 validity scales and their MMPI-2-RF counterparts were similarly effective in differentiating genuine responders from those exaggerating or feigning psychiatric and medical symptoms. These results provide reassurance for the use of both the MMPI-2 and MMPI-2-RF in settings where symptom exaggeration or feigning is likely. Findings are discussed in the context of the recently released MMPI-3.

Strategies of feigning mild head injuries related to validity indicators and types of coaching: Results of two experimental studies.

OBJECTIVE: In this paper, we analyzed differences between uncoached, symptom-coached, and test-coached simulators regarding strategies of feigning mild head injuries. METHOD: Healthy undergraduates (n = 67 in the first study; n = 48 in the second study), randomized into three simulator groups, were assessed with four experimental memory tests. In the first study, tests were administered face-to-face, while in the second study, the procedure was adapted for online testing. RESULTS: Online simulators showed a different approach to testing than face-to-face participants (U tests < 920, p < .05). Nevertheless, both samples favored strategies like memory loss, error making, concentration difficulties, and slow responding. Except for slow responding and concentration difficulties, the favorite strategies correlated with validity indicators. In the first study, test-coached simulators (m = 4.58-5.68, SD = 2.2-3) used strategies less than uncoached participants (m = 5.25-5.88, SD = 2.26-2.84). In the second study, test-coached participants (m = 3.8-5.6, SD = 1.51-2.2) employed strategies less than uncoached (m = 6.21-7.29, SD = 1.25-1.85) and symptom-coached participants (m = 6.14-6.79, SD = 1.69-2.76). DISCUSSION: Similarities and differences between online and face-to-face assessments are discussed. Recommendations to associate heterogeneous indicators for detecting feigning strategies are issued.

Dominance and inheritance patterns of mobility and death feigning in beetle strains selected for moving activity.

Reciprocal crossing of different strains is a suitable method to investigate the dominance and inheritance of a focal trait. Herein, we performed reciprocal crossing among strains of Tribolium castaneum exhibiting a genetically high (H strain) and low (L strain) moving activity and investigated the related heritable factors in the F1 and F2 generations. We also evaluated death-feigning behavior, which negatively responded to artificial selection for moving activity in T. castaneum. The results obtained for the F1 generation suggest that low moving activity and short duration of death feigning were dominant. In the F2 generation, movement and death feigning exhibited continuous segregation. The distribution of each trait value in the F2 generation differed from that in the parental generation, and no individuals transgressing the distribution of trait values in the parental generation emerged in the F2 generation. These results suggest that the genetic correlation between movement and death-feigning behavior is controlled in a polygenic manner. Moreover, the examination of the proportions of both behaviors (high vs. low moving activity and long vs. short death-feigning duration) in the F1 generation revealed that the two behaviors may be controlled by the maternal genotype, suggesting that the gene(s) that control movement and death feigning are located on the sex chromosome in T. castaneum.

Prevalence Estimates of Symptom Feigning and Malingering in Spain.

Symptom feigning and malingering should be evaluated in forensic contexts due to their important socio-economic consequences. Despite this, to date, there is little research in Spain that evaluates its prevalence. The aim of this study was to investigate this issue using the perception of the general population, students, and professionals of medicine and forensic psychology. Three adapted questionnaires were applied to a total of 1003 participants (61.5% women) from 5 different groups. Approximately two-thirds of participants reported knowing someone who feigned symptoms, and one-third disclosed feigning symptoms themselves in the past. Headache/migraine, neck pain, and anxious-depressive symptoms were the most commonly chosen. Experts in psychology and forensic medicine estimated a prevalence of 20 to 40% of non-credible symptom presentations in their work settings and reported not having sufficient means to assess the distorted presentation of symptoms with certainty. Professionals and laypersons alike acknowledge that non-credible symptom presentations (like feigning or malingering) are relevant in Spain and occur at a non-trivial rate, which compares with estimates in other parts of the world.

Detecting feigned ADHD in college students using the Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF).

Objective: To investigate the utility of the validity scales of the Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF) for detecting feigned Attention-Deficit Hyperreactivity Disorder (ADHD), we utilized a simulation design. Method: We examined group differences across the Restructured Clinical (RC) and validity scales as well as the classification ability of the validity scales across three cut scores. Analyses were conducted across five simulation groups (N = 177) and a standard instruction group (N = 32). Results: Across most of the RC and validity scales, those feigning ADHD produced significantly higher scores than the standard instruction group, but generally no significant differences between the feigning groups were demonstrated. The most promising scales for detecting feigned ADHD were F-r, Fp-r, and Fs at cut scores in the 70 T to 80 T range, respectively. Conclusions: Results support the use of the MMPI-2-RF in ADHD evaluations with scores on F-r, Fs, and Fp-r being particularly useful in detecting feigned ADHD in college students. However, there was no evidence to support the feigning of distinct ADHD symptoms presentations.

Validation of an adult ADHD measure of feigning in a sample including individuals with depression and anxiety symptoms.

Few studies of measures or techniques designed to detect feigning of Attention-Deficit/Hyperactivity Disorder (ADHD) have included groups reporting symptoms of depression and anxiety. Based on the high rate of comorbidity between ADHD and mood disorders, inclusion of such groups is important to mimic clinical referral patterns. The current study evaluated the validity of the ADHD Symptom Infrequency Scale (ASIS), a measure designed to detect malingered symptoms of ADHD, in a four-known groups design that included a group consisting of subjects with symptoms of anxiety and depression. Four groups were included in the current study: (1) control, (2) simulator, (3) ADHD diagnosed, (4) individuals with elevated symptoms of depression/anxiety. The ASIS Infrequency scale showed strong internal consistency (α = .83). Discriminant validity for the Infrequency Scale was established through a low correlation between the ASIS scale assessing feigning and a measure of anxiety and depression (r = -.02). Sensitivity was high for detection of simulation (.71), while specificity was high across comparisons, ranging from .86 to .99. Results support the ASIS as a reliable and valid measure of ADHD that is sensitive to feigning, even when including a sample of individuals reporting symptoms of depression and anxiety.

Polygene control and trait dominance in death-feigning syndrome in the red flour beetle Tribolium castaneum.

Death-feigning behavior is an anti-predatory technique used in several animal taxa and often correlates with inhibited movements (i.e., death-feigning syndrome). We performed a reciprocal crossing among strains exhibiting a genetically longer (L-strain) and shorter (S-strain) duration of death feigning. Then, we investigated related heritable factors in F1 and F2 populations. We also evaluated movement activities, which negatively responded to artificial selection for death feigning in T. castaneum. Our results indicated that death feigning occurred more frequently and for shorter periods in the F1 population. However, in the F2 population, death feigning and movement exhibited continuous segregation. Although the distribution of each trait value in the F2 generation differed from that of the parental generation, no individuals transgressing the distribution of trait values in the parental generation emerged from the F2 generation. Besides, chi-square analysis of the observed death feigning and movement of F1 and F2 progenies rejected the hypothesis of mono-major gene inheritance. These results suggested that the death-feigning syndrome was polygenically controlled, indicating the usefulness of reciprocal crossing experiments in assessing the quantitative inheritance of behavioral traits.

Responses to artificial selection for locomotor activity: A focus on death feigning in red flour beetle.

Whole-organism performance, including locomotor activity, is an important fitness trait in many animals. Locomotor activity is often classified into sprint speed and locomotor endurance and differences in sprint speed and locomotor endurance affect on other traits such as life-history traits. Previous studies found that locomotor endurance, sprint speed and brain dopamine (DA) levels are correlated with artificial selection for death feigning (an anti-predator behaviour that we refer to as 'death-feigning syndrome') in some insect species. Thus, if the syndrome has a genetic basis, death feigning, sprint speed and brain DA levels may be affected by artificial selection for locomotor endurance. We artificially selected for locomotor endurance over 10 generations in the red flour beetle Tribolium castaneum, and established higher (H) and lower activity (L) strains, then compared their death-feigning behaviour, sprint speed and brain DA levels. H-strain beetles exhibited significantly shorter duration of death-feigning, and significantly higher sprint speeds, suggesting variation in death-feigning syndrome. Surprisingly, although brain DA expression affects various animal behaviours, we found no significant differences in the brain DA expressions of H- and L-strain beetles. Thus, our results imply genetic correlations between locomotor endurance, sprint speed and death feigning, but not with brain DA expression, suggesting that differences in the biogenic amine results of our and previous studies may reflect differences in behavioural expression mechanisms.