PART I: PSYCHOLOGY AS AN EMPIRICAL SCIENCE, PSYCHOLOGICAL TESTS AND MEASUREMENTS

IF YOU HAVE a client with a head injury, or other associated psychological injury, it would be important to consider referring this person for a baseline neuropsychological or psychological examination. The reasons for this are compelling and overwhelming. Clinical Neuropsychology and Clinical Psychology represent a body of knowledge, habit of thought, area of applied research, and a clinical professional discipline, which is distinct from general medicine, neurology, neurosurgery, psychiatry, nursing, dentistry, education, special education, counseling, psychotherapy, etc.

Psychology is loosely defined as the scientific study of human behavior, and it entered the realm of empirical science with the study of individual differences and the development and implementation of psychological tests and measurements. Historically, psychology grew out of philosophy, physiology, and medicine. However, it was not until 1879 when a German physiologist named Wilhelm Wundt formally established the first psychological laboratory to study the "mind" (sensation and perception). Prior to this, psychology did not exist as an independent empirical science. Empirical science demands the collection of valid and reliable data collection or numbers. It was important to be able to move from naturalistic observation to hypothesis generation, formal experimentation, and statistical and data analysis of the results. (The logic of naturalistic observation, hypothesis generation, experimental design, formal experimentation, and statistical data analysis is the same or similar for all of the empirical sciences, including the behavioral sciences.) The field of test construction and the development of psychological measurement became a highly specialized and critical sub-specialty within psychology. Ann Anastasi (1940, 1950, and 1997) in her landmark work, "Psychological Testing", laid down the basic ground rules for psychological testing, particularly as tests are used in the clinical or applied setting. She was clearly the first, the best, and the most persistent to insist that, if clinical or applied psychology was to be considered a scientific discipline, then the psychological tests used must possess the qualities of validity and reliability, and there needed to be the development of standardized norms relevant to the population for which the test is used. The standardized norms are used to interpret an individual's test score. They represent divisions under the normal curve and are typically expressed as standard score, percentile, stanine, scaled score, and t score units.

The concept of test validity is defined as what the test measures, or what the test predicts. It is defined statistically as a correlation coefficient between two variables, typically the criterion measure and the variable under examination. The correlation coefficients typically range from +1.00 to -1.00. The higher the positive correlation, the greater the validity. For example, the IQ scores of the Wechsler Adult Intelligence Scale were validated with the IQ scores from the Stanford Binet Test of Intelligence. The validity coefficients between the Stanford Binet and the verbal IQ of the WAIS are .86, the performance IQ of the WAIS .69, and the full scale IQ of the WAIS .85. In test construction, the higher the validity coefficients, the better validity for the test. Nevertheless, it is also important to point out that the coefficient of correlation is an index of association and does not imply causality, i.e., the Standard Binet Test did not cause the verbal IQ score of the WAIS. In the development of a new test, validity coefficients in the range of .8 and above are expected and customary.

The concept of test reliability is theoretically defined as the consistency of results over time, or using alternate forms. Two different types of reliability are typically reported for psychological tests. This includes the test/re-test reliability of a test readministered to a group of subjects, for example, 3-6 months later. The second type of reliability reported is typically the split-half reliability, which expresses the extent to which different forms of the same test produce similar results. (The two forms of the test are often constructed by taking every other item on each of the portions of subtests of the main test.) Once again, the correlations of coefficients are calculated, and typically, correlations in the range of .9 or above are expected and customary for reliability coefficients.

Anastasi insisted that a psychological test used in the clinical or educational setting must have published standardized norms representing as closely as possible the clinical population for which the test is to be used. For example, the standardized norms developed for the WAIS, which was an extension and modification of the earlier Wechsler-Belleview Intelligence Scale, Form 1, developed a standardized sample by age, sex, geographic region, occupation, and educational level. (The stratified sample used was based on the US Census at the time.) It is important to note that the inclusion of all of these factors is particularly important in developing standardized norms for an ability test, which will be used with individuals at various ages (age 16 to old age) and educational levels.

It is also important to note that Anastasi severely criticized the use of the Thematic Apperception Test and the Rorschach(i.e. projective tests) on a clinical population, because they lacked the necessary qualities or attributes of acceptable test validity and reliability. This is particularly important in the forensic arena, and even with the development of the new "Exner" scoring system for the Rorschach, the criticisms and cautions advanced by Anastasi have endured and withstood the test of time.

Finally, in order to obtain valid and reliable test results, it is critically important that the test be administered and interpreted by someone, who has graduate level theoretical knowledge, and supervised clinical training and experience. The core doctoral curriculum in clinical psychology includes graduate level courses in Individual Differences, Psychological Tests and Measurements, Test Construction, Descriptive, Inferential and Multivariate Statistics, Experimental Design, and Research Methodology. The courses in psychological tests and measurements taken along with the research oriented courses prepare the doctoral candidates to develop a critical and in-depth understanding for the scientific basis for each test. The dissertation requirement taken along with the above courses allows the practicing psychologist to critically review the published journal literature throughout one professional life span. In addition the doctoral candidate must also complete a supervised clinical internship, which emphasizes the use of psychological tests, as well as the complete practice of psychotheraputic intervention techniques. No other healthcare discipline demands of candidates doctoral level competence in both the research and applied skills!

The American Psychological Association, the National Council on Measurement in Education, and the American Educational Research Association have jointly published the minimal standards for the ethical administration and interpretation of psychological tests to individuals in various settings. These include graduate level training in psychological tests and measurements, specific supervised training and practice, and licensing or certification in the jurisdiction, where the tests are to be administered. It is important to note that specialists in education, speech therapy, occupational therapy, and vocational rehabilitation also administer and interpret psychological tests. However, these professionals typically have completed graduate level courses in psychological tests and measurements as well as supervised training and practice in a specific defined professional arena. The American Psychological Association has been insistent that for psychologists to ethically administer and interpret psychological tests, it is important for the examiner to have doctoral level theoretical courses, supervised clinical training, pre or post doctoral internship, and licensing as a psychologist. Finally, "psychologists do not promote the use of psychological assessment techniques by unqualified persons." (APA, Ethics Code, 9.07) This is very important in the forensic arena, where the psychological/neuropsychological examiner will go into court and represent himself/herself as an "expert".

PART II: CLINICAL NEUROPSYCHOLOGY

Clinical neuropsychology is defined as the scientific study of brain-behavior or brain-cognitive relationships. The theoretical and clinical training required to competently carry out a clinical neuropsychological examination extends well beyond that of the typical doctoral program in clinical psychology. There are numerous training programs available throughout the US and Canada. The candidates or post-doctoral fellows/residents typically complete a one to two-year training program in clinical neuropsychology. The programs include post-doctoral courses in Neuroanatomy, Neurophysiology, and Neuropathology. It is important for the post-doctoral fellows to have a critical, in-depth understanding of the research basis for the administration and interpretation of the neuropsychological tests. The post-doctoral fellows are then trained to administer and interpret the neuropsychological tests on patients with a wide variety of neuropsychological and neurological disorders. Finally, many of the training programs now also introduce the post-doctoral students in neuropsychology to the most recent neurodiagnostic procedures used in medicine including CT, MRI, MRI(f), and PET scans of the brain, as well as the EEG examination.

In modern day clinical neuropsychology, there are three different theoretical and methodological approaches to clinical neuropsychological examination including the partial flexible battery approach, the Luria-Nebraska Battery, and the Halstead-Reitan and Reitan-Indiana Neuropsychological Test Batteries. Currently, there are major theoretical differences concerning, whether to use a fixed battery (as in the case of the Halstead-Reitan and Reitan-Indiana Neuropsychological Test Batteries) or to use a partial flexible battery (as is often used in the "Boston Process").

The Halstead-Reitan Neuropsychological Test Batteries are the most researched and widely used tests for assessing brain behavior relationships in adults and children. Each test in the Battery has been carefully validated through extensive research for sensitivity to cerebral cortical damage. The more than 30 validity studies, which have been published in the journal literature over the past approximate 50 years have conclusively demonstrated that the Halstead-Reitan Neuropsychological Test Batteries are sensitive to the type of lesion (traumatic brain injury, brain tumor, cerebrovascular disease, multiple sclerosis), location of lesion (focal versus diffuse damage, left cerebral hemisphere and right cerebral hemisphere, anterior-posterior within each cerebral hemisphere), and status of lesion (acute/active versus chronic/static). (Reitan, 1964) This body of research has firmly established the validity of the Halstead-Reitan Neuropsychological Test Batteries and is without equal in the research literature in applied psychology. In contrast, the partial/flexible battery approach has been criticized, because of its failure to generate validity data, and for its openness to examiner bias in test selection.

The Halstead-Reitan Neuropsychological Test Batteries have been developed to produce a comprehensive neuropsychological examination which evaluates sensory input, attention, concentration and memory abilities, verbal and language skills, visual-spatial and manipulatory functions, abstract reasoning, logical analysis, planning abilities, and motor output. These batteries meet and exceed the most stringent neuropsychological test criteria as follows:

1. They assess the full range of cognitive and adaptive skills dependent upon organic brain function.
2. They evaluate both general and specific areas of cerebral cortical function.
3. They allow for several methods of traditional neuropsychological inference.
4. The tests are carefully validated for sensitivity to cerebral cortical damage.
5. They provide the equivalent representation of both cerebral hemispheres yielding a balanced interpretation of degree of deficit for adults (Reitan and Wolfson, 1988) and children (Reitan, 1987).

The neuropsychological examination differs significantly from the neurological exam. Furthermore, it has now been well established that the neuropsychological test results have a life of their own quite apart from the neurological findings. It is quite common to find patients with closed head injuries to have completely normal neurological examinations, and this includes the physical examination, MRI or CT scan of the brain, and EEG examination, and yet demonstrate serious continuing deficits on the neuropsychological examination. In addition, the medical specialties have not developed methods to differentially distinguish organically based complaints from emotionally based complaints (Reitan & Wolfson, 2000). Nevertheless, in clinical neuropsychology using the Halstead-Reitan Neuropsychological Test Batteries, and the MMPI-2 or MMPI-A, this can be done with confidence.

PART III: THE FORENSIC NEUROPSYCHOLOGICAL EXAMINATION

The forensic neuropsychological examination differs significantly from the usual clinical neuropsychological examination because it represents a much more comprehensive evaluation with emphasis on the use of valid and reliable tests which are critically interpreted within the context of the patient's pre and post-injury history and personality makeup. This will allow the forensic examiner to objectively determine the facts, and from which to offer an expert opinion.

In the forensic neuropsychological examination, it is important to establish as accurately as possible the patient's pre-injury cognitive, memory, and emotional functioning. In most cases, this can very effectively be carried out by an in-depth examination of the injured patient's educational record, pre-injury medical record, and work history. The educational record will often provide the patient's pre-injury academic performance in the classroom, standardized test results, and in some cases, the results of a psychological evaluation will be in the educational record. An examination of the patient's pre-injury medical history, mental health history, and alcohol and substance use history also provide important information. Finally, an examination of the patient's recent work history and work performance records, if available, can also provide very valuable pre-injury cognitive and emotional data on the patient. A comprehensive review of all of this information will most often allow the examiner to rule out, or rule in, pre-existing evidence of constitutional brain deficits, a learning disability, emotional or behavioral problems, alcohol and substance abuse, or any other brain injury or disease.

It is critically important to determine as accurately as possible the specific nature and extent of the "alleged" head injury. Therefore, it will be necessary to carefully review all of the medical and police records, including the records from the EMT, the police report, the emergency room and other hospital records, and any follow-up medical records from the patient's primary care physician or neurologist, etc. Finally, the reports of any witnesses to the accident, as well as the patient's subjective report, are also important.

The completion of the neuropsychological testing examination on the patient should be carried out as soon as possible after the injury. The reasons for this are related to the fact that research has firmly established that the patient will show the greatest amount of recovery of neuropsychological functions in the area of greatest initial deficit. Nevertheless, considering our current healthcare system, the patient is often six months to one year post-injury before he/she finds his/her way to the office of a clinical neuropsychologist. Furthermore, if the patient survives the injury, it is likely that there will be some recovery of cognitive and neuropsychological functions. Nevertheless, this can vary markedly from one patient to the next, and most patients with continuing and enduring symptoms also develop a post-accident depression and/or post-traumatic stress disorder. The comprehensive neuropsychological examination will be able to address all of these issues and should be carried out as soon as the patient is able after the head injury. Finally, a clinical neuropsychologist, who has had extensive experience carrying out in-depth neuropsychological examinations on patients with a wide variety of brain disorders, including traumatic brain injury, demyelinating disease, Parkinson's disease, cerebrovascular disease, brain tumors, and the effects of excessive alcohol or substance use, can often infer from the neuropsychological test results themselves without the benefit of any history that the patient has sustained a traumatic brain injury. It is important to note that research findings have established specific patterns of neuropsychological test results for all of the above conditions on the Halstead-Reitan Neuropsychological Test Batteries.

Finally, and most importantly of all, it is important for the forensic neuropsychological examiner to be able to establish or rule out a causal link between the alleged head injury and the identified neuropsychological deficits and emotional dysfunction. Furthermore, at this juncture, it is critically important to factor in any pre-existing neuropsychological deficits or emotional problems, and this will give added credibility to the expert's opinion. Establishing or ruling out the causal relationship beyond a reasonable neuropsychological certainty can usually be accomplished using both exclusive and inclusive logic or inference. If the patient's educational, medical, substance use, and employment history is clean and without incident, this will provide solid support for the conclusion, that there was no significant pre-existing condition. However, even in cases where there is evidence of a pre-existing condition such as congenital deficits, a learning disability, or childhood meningitis, it may be possible to demonstrate that such a condition could not explain the current identified neuropsychological deficits. This would be particularly true if the patient/client was doing well in school or on the job immediately prior to the head injury. Furthermore, one could also argue that a patient with a pre-existing condition would be less able to adequately ward off, tolerate, or recover from the effects of a closed head injury. The specific pattern of neuropsychological test results on the Halstead-Reitan Battery will also provide important information to allow the expert to rule in or rule out a causal inference. Finally, the most recent and the best neuropsychological research supports the conclusion that patients who have sustained an earlier head injury are less able to recover fully from a more recent or current head injury. In addition, this same body of research also supports the conclusion that many patients who have sustained a mild to moderate closed head injury will fully recover. However, this varies markedly from patient to patient, and this same body of research supports the conclusion that approximately 10-20% of the patients, who sustain a mild to moderate closed head injury will demonstrate significant neuropsychological deficits 12-18 months after the head injury. This evidence is very compelling, because in most cases the medical and neurological findings are entirely normal.

PART IV: SUMMARY AND CONCLUSIONS

Psychology is the scientific study of individual differences in human behavior. The applied fields of clinical neuropsychology and clinical psychology use valid and reliable tests with published norms to objectively evaluate patients with a variety of difficulties. Historically, it was critically important to be able to move from subjective clinical observation to the objective measurement of the patient's deficits or emotional difficulties. Patients can now be objectively tested and diagnosed as more or less functional or impaired. In this sense the applied fields of psychology bring a unique perspective to the entire healthcare arena. The forensic neuropsychological examination is a comprehensive evaluation using valid and reliable neuropsychological tests, which are critically interpreted within the context of the patient's pre and post-injury history and personality makeup. Clinical neuropsychology came into existence approximately 50 years ago, because patients who had sustained injury or disease to the brain were cleared to return to work or school by their health care providers. Nevertheless, a significant proportion of these patients reported enduring neuropsychological deficits 12-18 months after sustaining a brain injury. Over the years, neuropsychologists developed and validated neuropsychological tests, which were found to be sensitive to type, location, and status of brain lesion. Most importantly, the Halstead-Reitan Neuropsychological Test Batteries produce a comprehensive neuropsychological examination which evaluates sensory input, attention, concentration and memory abilities, verbal and language skills, visual-spatial and manipulative functions, abstract reasoning, logical analysis, planning abilities, and motor output. In other words, the neuropsychological examination evaluates all of the skills necessary for adaptive living. It is now well recognized that the neuropsychological test results have a life of their own quite apart from the neurological findings. The minimum requirements for carrying out a neuropsychological examination in the forensic arena include doctoral-level training in applied psychology and post-doctoral training in Clinical Neuropsychology. It is also important for the neuropsychologist who wishes to work in the forensic arena to have a minimum of five years of experience carrying out neuropsychological examinations on patients with a wide variety of brain disorders, including traumatic brain injury. The reason for this is that it is important to be able to distinguish these disorders objectively on the basis of the pattern of neuropsychological test results independent of the patient's medical history and subjective report. Finally, it is important for the clinical neuropsychologist working in the forensic arena to obtain ongoing experience as an expert witness testifying at depositions, Labor Board hearings, and in court. It is clear that the science and practice of clinical neuropsychology is distinct from that of the medical specialties in neurology, neurosurgery, and psychiatry, and has a major enduring contribution to make to fair and just litigation in head injury cases.

Ernest C. Desjardins, Ph.D, is a clinical and forensic neuropsychologist based in Portsmouth. He has carried out more than 2,200 neuropsychological and psychological examinations on adults and children over an approximate 30-year period with emphasis in closed head injury cases. He can be reached in his Portsmouth office at 603-431-1672.

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