30 clinical neuropsychologists worked on a Consensus Conference Statement, by all sharing and discussing their relevant knowledge about neuropsychological assessment of effort, malingering and response bias.

Detection vs. Diagnosis

A distinction between detection and diagnosis can be made when there is a concern about insufficient effort or malingering during an assessment. Detection can occur during any neuropsychological assessment. Examinees may undermine the validity of the assessment by intentionally creating the appearance of disability or exaggeration of their symptoms. They show problems with effort: problematic effort. The Symptom Validity Test is an effort test which measures performance or response validity. They are aimed to identify a negative response bias. The use of psychometric indicators is the most valid approach to identifying neuropsychological response validity.

Diagnosis means that the clinician is explicitly making a determination of intent. There is a consensus that malingering can be diagnosed in some examinees through the application of relevant psychological and neuropsychological science. The committee explicitly recommends the use of multiple sources of data and information. When making a diagnosis, empirically based systems are recommended, because of the increase in reliability they provide considering validity indicators. The committee agrees with the findings of the DSM-IV-TR that malingering is not a disorder or mental illness. When malingering is diagnosed, it is used as a descriptive term for intentional exaggeration. It is important that practitioners keep their knowledge about scientifically based inferences about the behavior of examinees up to date. A distinguishing must be made between scientifically based clinical decisions and legal adjudication.

Issues concerning abilities

A response bias is the mispresentation of abilities in any neuropsychological domain of ability through performance or self-report regarding performance abilities. When the valence of the response bias is negative and the potential for external gain is present, malingering should be considered. Negative response bias is operationalized by failure to surpass the thresholds of effort tests or embedded validity indicators. Disparity between test performance and real-world behavior could represent response bias. In this case, the possibility of false or incomplete history should be considered. Tests and other psychometric procedure relied on by clinicians in judging response validity must themselves have proven validity.

Assessment methods related to evaluating response validity

Stand-alone cognitive effort tests have been specifically developed to measure task performance validity. They have shown to be extremely useful in forensic settings, where there are high risks of invalid responding. Stand-alone cognitive effort tests can consist of forced-choice items or non-forced choice items. The latter allows a range of responses and may evaluate random responding, erroneous or unrealistically slow responding and inconsistency of response patterns in comparison with performances from well-documented disorders. Forced-choice items offer the opportunity to look at chance-level performance.

Embedded indicators within ability tests are validity indicators derived from standard clinical ability tests that have shown to be useful in detecting dishonest performances. The committee recommends using both stand-alone effort measures and embedded validity indicators.

Self-reports also need to be evaluated using psychometric instruments which contain proven validity measures. By using disorder-specific inventories, practitioners can compare an individual’s response with responses of patients who experience the same symptoms or who have been given the same diagnosis. They do so by looking at validity scales like severity of symptoms and specificity.

General personality inventories are not equivalent in application to all conditions, so clinicians should be aware of all relevant research. When a practitioners suspects response bias, either negative or positive, they should be cautious when interpreting the clinical scales of this test.

In order to produce valid results, sufficient effort is needed on every ability test. Effort is a dynamic concept, which therefore may vary throughout the examination. Ideally, effort should be measured repeatedly or continuously throughout the examination. Also, when indicators of malingering are found, this doesn’t mean all symptoms can be explained by malingering. Determining whether the malingering is wholly or only partly explanatory for the symptoms is specific to the current case evaluation. Regardless of the conclusion about malingering, when examiners find evidence for negative response bias, determinations like ‘invalid’ can be made. Like with all types of psychological assessment, neuropsychologists should encourage optimal effort.

The malingering of psychological symptoms can occur independently of malingering physical or cognitive abilities. Therefore, assessment methods that can evaluate both are necessary. Unfortunately, objective standards evaluating inconsistencies between test performances and real-world behavior do not really exist. Therefore, conclusions need to be drawn cautiously.

Documentation within reports

The committee recommends neuropsychologists to list the symptom validity measures and procedures they used in evaluations. They should explain on which grounds they based their opinions, while avoiding inclusion of specific information pertaining to these measures that could preclude valid future use. A decision not to use effort tests and embedded validity indicators would only rarely be justified, but if this would be the case clinicians should enlist and elaborate his decision. It does happen that clinicians are unable to use such measures because of time constraints, administrative prohibition or the individual being evaluated is not appropriate to be given such measures (for example in case of mental retardation). One should always document the reasons for not using appropriate response validity measures.

Recommendations for future research related to assessment of abilities

• Populations at risk of failing effort tests despite their best effort should be investigated

• Methods to show evidence of deliberate intent to feign should be developed

• Effort validity tests should be applied to paediatric samples

• A definition of when the risk of response bias is ruled out is needed

• New ability tests should have validity indicators created at time of test construction

Somatic issues

When assessing for non-credible somatic symptoms, the committee recommends using multiple well-validated measures covering domains of self-report, performance and symptom validity. As the number and extend of findings consistent with absence or presence of response bias increase, the conclusions about the validity of the examination increases in confidence. Response validity regarding somatic symptoms relates to excessive subjective disability which patients attribute to somatic dysfunction. This can occur in multiple somatic domains, like claimed impairment of motor skills and sensory/perceptual impairment. Concerning somatic symptoms, it is especially important to rule out any false-positives for malingering. Accusing someone of malingering while the somatic symptoms are real can have disastrous consequences. In order to come to a founded conclusion, the patient’s history information should be evaluated for accuracy and completeness.

Recommendations for future research related to somatic issues

• Further research is necessary in order to form criterion groups of malingerers independently of dependent variables.

• There should be strict inclusion and exclusion criteria for investigations. For instance, control groups should consist of patients without known external incentives. Criterion groups should consist of patients with little or no evidence for pathology, combined with illogical symptom histories.

• A multidisciplinary approach is necessary in order to optimize functional capacity measures.

• The influence of demographic variables, like gender, should be further investigated.

Psychological issues

Psychological or psychiatric disorders that may be seen in evaluations of patients who are claimants in secondary gain contexts are referred to as ‘psychological issues’. It is important to look at the totality of the patient’s symptom presentation and personal (family)history when assessing the validity of claims of psychopathology and/or emotional distress. Keeping the diagnostic criteria in mind, an examiner can conclude whether the patient’s presentation is or isn’t compatible with what is known about the disorder. Onset of the disorder and symptom presentation are important diagnostic features. The degree of which symptom presentations follows a course or pattern over time that is typical or atypical of the disorder can also be revealing. Finally, the practitioner should consider the possibility of incorrect prior diagnosis when a patient’s documented history indicates a formal diagnosis. Investigating whether the patient sought appropriate treatment and whether he or she responded to the treatment can be helpful. It is strongly advised to use multiple recourses, like in-depth interviews, observations of behavior, history, collateral interviews and scientific assessments.

Recommendations for future research related to psychological issues

• Further research on the relationship between genuine psychopathology and invalid response patterns is necessary.

• New instruments and scales to detect response bias should be developed and emotional and cognitive response validity issues in known psychiatric groups need further investigation.

• More research considering invalid self-reports in cases of psychopathology is necessary to understand individual differences