Examining the utility of a clustering method for analysing psychological test data

The belief that certain disorders will produce specific patterns of cognitive strengths and weaknesses on psychological testing is pervasive and entrenched in the area of clinical neuropsychology, both with respect to expectations regarding the behaviour of individuals and clinical groups. However, there is little support in the literature for such a belief. To the contrary, studies examining patterns of cognitive performance in different clinical samples without exception find more than one pattern of test scores. Lange (2000) in his comprehensive analysis of WAIS-R/WMS-R data for a large sample of mixed clinical cases found that three to five profiles described variations in test performances within clinical diagnoses. Lange went on to show that these profiles occurred with approximately equal frequency in all diagnostic groups. He additionally found four profiles in an exploratory analysis of WAIS-III/WMS-III data from a similar sample. The goals of the current dissertation were to: a) replicate Lange’s findings in a larger clinical sample; b) extend the scope of these findings to a wider array of psychological tests; and c) develop a method to classify individual cases in terms of their psychological test profile. The first study assessed 849 cases with a variety of neurological and psychiatric diagnoses using hierarchical cluster and K-Means analysis. Four WAIS-III/WMS-III profiles were identified that included approximately equal numbers of cases from the sample. Two of these profiles were uniquely related to two of Lange’s profiles, while the remaining two demonstrated relationships with more than one of Lange’s clusters. The second study expanded the neuropsychological test battery employed in the analysis to include the Trail Making Test, Boston Naming Test, Wisconsin Card Sorting Test, Controlled Oral Word Association Test, and Word Lists from the WMS-III reducing the number of clinical cases to 420. In order to compensate for the impact of the reduced number of cases and increased number of variables on potential cluster stability, the number of test score variables was reduced using factor analysis. In this manner the 22 variables were reduced to six factor scores, which were then analysed with hierarchical cluster and K-Means analysis yielding five cognitive profiles. The third study examined the potential clinical utility of the five cognitive profiles by developing a single case methodology for allocating individual cases to cognitive profiles. This was achieved using a combination of a multivariate outlier statistic, the Mahalanobis Distance, and equations derived from a discriminant function analysis. This combination resulted in classification accuracies exceeding 88% when predicting the profile membership based upon the K-Means analysis. The potential utility of this method was illustrated with three age-, education-, gender-, and diagnostically-matched cases that demonstrated different cognitive test profiles. The implications of the small number of cognitive profiles that characterise test performance in a diverse sample of neurological and psychiatric cases as well as the clinical utility of an accurate classification method at the individual case level was discussed. The role of such a classification system in the design of individualised rehabilitation programmes was also highlighted. This research raises the intriguing possibility of developing a typology based on human behaviour rather than a medical nosology. In effect, replacing the medical diagnosis so ill-suited to encompassing the complexities of human behaviour, with a more appropriate “psychological diagnosis” based on cognitive test performance

What Do We Know About Neuropsychological Aspects Of Schizophrenia?

Application of a neuropsychological perspective to the study of schizophrenia has established a number of important facts about this disorder. Some of the key findings from the existing literature are that, while neurocognitive impairment is present in most, if not all, persons with schizophrenia, there is both substantial interpatient heterogeneity and remarkable within-patient stability of cognitive function over the long-term course of the illness. Such findings have contributed to the firm establishment of neurobiologic models of schizophrenia, and thereby help to reduce the social stigma that was sometimes associated with purely psychogenic models popular during parts of the 20th century. Neuropsychological studies in recent decades have established the primacy of cognitive functions over psychopathologic symptoms as determinants of functional capacity and independence in everyday functioning. Although the cognitive benefits of both conventional and even second generation antipsychotic medications appear marginal at best, recognition of the primacy of cognitive deficits as determinants of functional disability in schizophrenia has catalyzed recent efforts to develop targeted treatments for the cognitive deficits of this disorder. Despite these accomplishments, however, some issues remain to be resolved. Efforts to firmly establish the specific neurocognitive/neuropathologic systems responsible for schizophrenia remain elusive, as do efforts to definitively demonstrate the specific cognitive deficits underlying specific forms of functional impairment. Further progress may be fostered by recent initiatives to integrate neuropsychological studies with experimental neuroscience, perhaps leading to measures of deficits in cognitive processes more clearly associated with specific, identifiable brain systems

Methods of Detecting Malingering and Estimated Symptom Exaggeration Base Rates in Australia

Neuropsychology malingering base rates have not been widely investigated in Australia. Estimates in North America vary with as many as 4 in 10 people evaluated for personal injury or compensation cases suspected of exaggerating symptoms. Data on Australian neuropsychology symptom exaggeration base rates were estimated using a modified and expanded version of a survey previously designed for this purpose (Mittenberg, Patton, Canyock, & Condit, 2002). Figures were based on an estimated 1818 annual cases involved in personal injury, (n = 542), disability (n = 109), criminal (n = 108), or medical (n = 1059) matters. Symptom exaggeration base rates associated with referral type and diagnoses were variable. Specifically, 17% of criminal, 13% of personal injury, 13% of disability or workers compensation, and 4% of medical or psychiatric cases were reported to involve symptom exaggeration or probable symptom exaggeration. The highest rates of symptom exaggeration included cases referred for mild head injury (23%), pain or somatoform disorders (15%), moderate to severe head injury (15%), and fibromyalgia or chronic fatigue (15%). Overall, Australian symptom exaggeration base rates reported in this study were lower compared with base rates previously reported in North America

Adjudicative competence

PURPOSE OF REVIEW: Although the basic standards of adjudicative competence were specified by the U.S. Supreme Court in 1960, there remain a number of complex conceptual and practical issues in interpreting and applying these standards. In this report we provide a brief overview regarding the general concept of adjudicative competence and its assessment, as well as some highlights of recent empirical studies on this topic. FINDINGS: Most adjudicative competence assessments are conducted by psychiatrists or psychologists. There are no universal certification requirements, but some states are moving toward required certification of forensic expertise for those conducting such assessments. Recent data indicate inconsistencies in application of the existing standards even among forensic experts, but the recent publication of consensus guidelines may foster improvements in this arena. There are also ongoing efforts to develop and validate structured instruments to aid competency evaluations. Telemedicine-based competency interviews may facilitate evaluation by those with specific expertise for evaluation of complex cases. There is also interest in empirical development of educational methods to enhance adjudicative competence. SUMMARY: Adjudicative competence may be difficult to measure accurately, but the assessments and tools available are advancing. More research is needed on methods of enhancing decisional capacity among those with impaired competence

What Do We Know About Neuropsychological Aspects Of Schizophrenia?

Application of a neuropsychological perspective to the study of schizophrenia has established a number of important facts about this disorder. Some of the key findings from the existing literature are that, while neurocognitive impairment is present in most, if not all, persons with schizophrenia, there is both substantial interpatient heterogeneity and remarkable within-patient stability of cognitive function over the long-term course of the illness. Such findings have contributed to the firm establishment of neurobiologic models of schizophrenia, and thereby help to reduce the social stigma that was sometimes associated with purely psychogenic models popular during parts of the 20th century. Neuropsychological studies in recent decades have established the primacy of cognitive functions over psychopathologic symptoms as determinants of functional capacity and independence in everyday functioning. Although the cognitive benefits of both conventional and even second generation antipsychotic medications appear marginal at best, recognition of the primacy of cognitive deficits as determinants of functional disability in schizophrenia has catalyzed recent efforts to develop targeted treatments for the cognitive deficits of this disorder. Despite these accomplishments, however, some issues remain to be resolved. Efforts to firmly establish the specific neurocognitive/neuropathologic systems responsible for schizophrenia remain elusive, as do efforts to definitively demonstrate the specific cognitive deficits underlying specific forms of functional impairment. Further progress may be fostered by recent initiatives to integrate neuropsychological studies with experimental neuroscience, perhaps leading to measures of deficits in cognitive processes more clearly associated with specific, identifiable brain systems

Malingering base rates and detection methods in Australia

Neuropsychology malingering base rates have not been widely investigated in Australia. Estimates in North America vary with as many as 4 in 10 people evaluated for personal injury or compensation cases suspected of exaggerating symptoms. Data on Australian neuropsychology symptom exaggeration base rates were estimated using a modified and expanded version of a survey previously designed for this purpose (Mittenberg, Patton, Canyock, & Condit, 2002). Figures were based on an estimated 1818 annual cases involved in personal injury, (n = 542), disability (n = 109), criminal (n = 108), or medical (n = 1059) matters. Symptom exaggeration base rates associated with referral type and diagnoses were variable. Specifically, 17% of criminal, 13% of personal injury, 13% of disability or workers compensation, and 4% of medical or psychiatric cases were reported to involve symptom exaggeration or probable symptom exaggeration. The highest rates of symptom exaggeration included cases referred for mild head injury (23%), pain or somatoform disorders (15%), moderate to severe head injury (15%), and fibromyalgia or chronic fatigue (15%). Overall, Australian symptom exaggeration base rates reported in this study were lower compared with base rates previously reported in North America