Reading time: 3 minutes, 44 seconds (927 words)
Performance validity tests (PVTs) are psychological measures designed to assess whether a person may be putting little effort during cognitive testing and feigning poor performance.
People with low IQ often score poorly on PVTs, as these measures were not created for or validated on people with low IQ. Thus, they are often falsely classified by PVTs as feigning when they are, in fact, providing genuine effort.
Forensic psychologists and psychiatrists can avoid misinterpreting PVT results by being aware of how people with low IQ may respond during testing and how their scores may be affected by their disability.
One study showed that individuals with an IQ lower than 70 (the extremely low range of IQ) fail at least one performance validity test, and those with an IQ of 60 to 69 fail an average of three tests.
Malingering and Masking
Feigning of psychological or physical symptoms that is motivated by external incentives is called malingering. In her presentation for the International Forensic Psychiatry Lecture Series, Dr. Sara Millspaugh said accused people may feign intellectual impairments to have charges dropped or, in the United States, to avoid the death penalty, as people with an intellectual disability (ID) cannot be executed.
However, people with low IQ tend to do the opposite. They often attempt to hide or minimize their impairments (called masking), by saying they understand discussions with their lawyer, what occurs in court, and legal jargon, when they do not.
They may mask because they have been bullied and abused because of their impairments in the past. In some cases, people with an ID have masked their low intellectual and adaptive functioning even though it means they might face the death penalty.
Performance Validity Tests
Dr. Millspaugh gives the person a series of PVTs in a specific order, so if the person performs well on a test, she does not proceed with further tests as that shows they are not feigning. However, if their performance is poor, she continues until she has enough data to opine whether the person is feigning.
These tests include:
- For cognitive testing in all contexts (criminal and non-criminal):
- The Test of Memory Malingering (TOMM)
- The Dot Counting Test (DCT)
- The Rey 15-Item Test (FIT)
- The Validity Indicator Profile (VIP)
- For fitness to stand trial evaluations:
- The Test of Malingered Incompetence – General Knowledge and Legal Knowledge (TOMI-G and TOMI-L)
- The Inventory of Legal Knowledge
There are also some PVTs embedded in other general cognitive tests, such as the Reliable Digit Span (RDS), which is part of the Wechsler Adult Intelligence Scales (WAIS).
PVT scores that are below a certain cut-off usually indicate possible feigning. However, research showed that these cut-off scores do not accurately identify whether a person with low IQ is feigning. Different cut-off scores should be used for these individuals. For example, the normal cut-off score for the TOMM is 45 or above on Trial 2 and Retention. However, two studies have shown that the cut-off score for people with low IQ should be 30.
Administering Cognitive Testing
Administering these tests to people with low IQ who have been accused of a crime can present challenges. They may have difficulty completing the tests because of:
- stress related to their legal situation and possible consequences,
- poor performance on previous tests in school,
- difficulties paying attention,
- reactions to the evaluator’s words and behaviour, and
- other conditions (e.g., pain or depression).
They may decide not to take tests they believe they will fail, or they may not be able to complete a test because of significant distress.
Dr. Millspaugh gave an example of a person who became very distressed when he did not understand something during the interview and testing session. During testing, he made less eye contact with the administrator when he felt anxious or frustrated. When encouraged to make a guess, he did not want to. Because of these observations, cognitive testing was not administered. Dr. Millspaugh determined she had enough other evaluation data from the interview, collaterals, and testing to opine he likely had low IQ and was not fit to stand trial.
When giving tests to people with low IQ, Dr. Millspaugh says clinicians need to be patient. They should allow the person to take breaks as needed. Clinicians should make sure the person understands what is going on throughout the testing. They should encourage people to try their best and guess instead of saying they do not know because the purpose of the evaluation is to assess how much the person knows and understands.
Integrating All Information
Dr. Millspaugh’s standard evaluation process involves interviewing the person, administering tests, and collecting collateral information. For fitness to stand trial evaluations, the most important collateral data are records and information from the person’s lawyer about their current functioning. When possible, Dr. Millspaugh also obtains information from people who know the person to get information about the person’s intellectual and adaptive functioning abilities. This information can confirm what the tests indicate and correct any false impressions.
To reach a conclusion, forensic psychologists and psychiatrists must integrate all information. Clinicians should never conclude that someone is malingering based on a single test score or data point, Dr. Millspaugh stressed.
For more details, watch the recording of the February 6, 2026, lecture, “Administering and Interpreting Performance Validity Tests (PVTs) for Individuals with Suspected Low Intellectual Functioning” on our website.
Written by Carolyn Brown and Dr. Sara Millspaugh.
