The validity indicator profile (VIP) is a measure of response validity that is intended to be administered concurrently within a battery of cognitive tests in a forensic assessment. The VIP has two subtests (verbal and nonverbal), containing 178 items in all. Curve analysis of test responses classifies performance as valid or invalid. Invalid performances are subclassified as inconsistent, irrelevant, or suppression (obvious malingering). The VIP has been validated in several adult samples.
Forensic psychological testing often involves assessment of cognitive functioning. Given the inherent advantages of appearing impaired in many forensic forums (e.g., litigated claims of injury, competency to stand trial), it is important to provide a formal assessment of the validity of test performance. Forensic assessments that conclude that cognitive impairment exists are below the standard of practice if they do not include overt assessment of the validity of presentations in interviews or on psychological tests. A large variety of response validity instruments exist. Most response validity instruments depend on assessment of memory performance. The VIP directly assesses problem-solving ability and vocabulary.
Performance on the VIP is categorized as valid or invalid. Valid performances, referred to as compliant, reflect an intention to perform well and reveal sustained effort throughout the test. Invalid performances are classified as inconsistent, irrelevant, or suppressed.
Inconsistent performances reveal evidence of intention to respond correctly but reflect inconsistent effort. Irrelevant performances result from random responding throughout the test. Performances classified as suppressed demonstrate that the individual intended to respond incorrectly on the test and exerted sustained effort to respond incorrectly.
These classifications reflect a model of test validity in which validity is evaluated by a cross-classification of “intent” (intends to respond correctly or does not intend to respond correctly) and “effort” (low to high). Although most “malingering tests” in use are referred to as “effort” tests and employ a dichotomous classification process that generally is construed to mean “malingering” or “not malingering,” the VIP employs a fourfold classification scheme to capture elements of these two constructs. Construct validation of this scheme demonstrates that compliant and inconsistent performances could be distinguished on the basis of effort, that inconsistent and irrelevant performances could be distinguished on the basis of intent, and that compliant and suppressed performances could be distinguished on the basis of intent.
The categorizations are accomplished by performance curve analysis. The performance curves are a summary of response accuracy plotted against item difficulty. The VIP has two subtests, nonverbal and verbal. The nonverbal subtest includes 100 picture-matrix problems, and the verbal subtest includes 78 word-definition problems. The items within each subtest span a hierarchy of difficulty, from very easy to very difficult. The items are presented in a randomized order of difficulty. The test is typically completed by paper and pencil, but the publisher also provides a means for computer testing.
The test takers must complete all the items, each of which has two answer choices. Once the test is completed, the answers are scored (0 or 1), and they are reordered by item difficulty. Spans of 10 scores are averaged, using running means, to yield performance curves comprising 91 (nonverbal) or 69 (verbal) points. For example, Items 1 to 10 yield the first running mean, and Items 2 to 11 yield the second running mean. In a VIP performance curve, the x value of the performance curve is item difficulty, and the y value is mean performance accuracy (running mean value).
When a line is plotted through the running means, the resulting performance curve yields distinctive features that are used to categorize performance. The first general feature is the slope of the performance curve. The curves that have a downward slope from easy to difficult reveal intent to respond correctly. The flat curves reflect irrelevant responding, and the upward sloping curves reflect intent to respond incorrectly. The extent to which these slopes are sustained provide information about application of effort. The first running mean is also an indicator of intent, as that point of the curve reflects performance on the 10 easiest items. These items are easily answered by young children. The test includes items that are not easily answered by most individuals so that a transition from effortful performance to guessing can be observed. The fluctuations in the expected progression of the performance curve from consistent correct responding to guessing, given the ability level of the individual, and identify instances of inconsistent responding. That is, these fluctuations are meaningful irrespective of the inherent capacity of the individual to respond correctly.
For classifications of compliant, inconsistent, and suppressed, it is possible to estimate the intellectual capacity of the individual. The characteristics of the performance curve and the number of items correctly responded to have been correlated with performances on other intellectual measures. It is noteworthy that these features are applicable when individuals intentionally choose incorrect answers and are classified as suppressed.
Validation studies have been reported in four published papers and the test manual. Validation and cross-validation samples have included large numbers of normal adults, neuropsychology examinees, criminal defendants, and persons with serious mental illness.
The reported classificatory accuracy of the nonverbal subtest is 66% sensitivity and 90% specificity. The verbal subtest demonstrates 59% sensitivity and 94% specificity.
- Frederick, R. I. (2003). The validity indicator profile (2nd ed.). Minnetonka, MN: NCS Pearson.
- Frederick, R. I., Crosby, R. D., & Wynkoop, T. F. (2000). Performance curve classification of invalid responding on the Validity Indicator Profile. Archives of Clinical Neuropsychology, 15, 281-300.
- Ross, S. R., & Adams, K. M. (1999). Test review: One more test of malingering? Clinical Neuropsychologist, 13, 112-116.