Proposal for a new tool assessing validity performance in forensic neuropsychological testing: the Test of Malingering in Abstraction Skills (TOMAS)

Objective: the assessment of malingering in forensic neuropsychological testing can be supported by the use of performance validity tests (PVTs). When designing PVTs, test material should be easy enough to be insensitive to real cognitive dysfunction, but at the same time difficult enough not to appear overtly as a measure of poor effort. In the present paper, we aimed at proposing a new instrument, the Test of Malingering in Abstraction Skills (TOMAS), for detecting poor effort possibly due to malingering in forensic neuropsychological assessment; in designing the instrument, we ensured that the test had a credible level of difficulty to keep satisfactory sensitivity. Method: the TOMAS was developed as a standalone tool utilising items selected from standardised and validated neuropsychological tests assessing verbal abstraction skills. In three studies we developed the final version of the test, assessed its association with demographic and cognitive variables, and estimated its sensitivity, specificity and criterion validity in comparison with the Rey 15-items test using a simulation paradigm involving healthy participants. Results: the final version of the TOMAS includes two sections (Part A and Part B) providing multiple indexes that have an adequate discriminating power, with satisfactory sensitivity and specificity values; the discriminating power of the TOMAS is higher than that of the Rey 15-items test. Conclusion: the multiple indexes provided by the TOMAS may support clinicians in assessing poor effort during neuropsychological examination. Future evidence is needed to fully establish the validity of the instrument in clinical and forensic samples.