What Testing CAN’T Tell You

Psychological testing is a great tool but it isn’t without flaws. Yes, just about anything can be addressed using psychological testing, but it doesn’t mean everything SHOULD be. Psychological testing isn’t a tarot card reading or a medical lab test. It doesn’t always provide the clear-cut answers people expect.


To test, or not to test.

At times, people use testing to make decisions. If the reason for doing testing in the first place is to stigmatize or scapegoat, then more harm than good will come from the process. That’s not rocket science, of course, but sometimes the REAL intent is hidden under the guise of “just wanting to know.” The purpose of testing is to benefit the examinee by providing information that would help create a plan for moving forward. Ideally, the process would help to instill hope and a sense of empowerment. If the real reason is to find someone to blame, it’s best to skip it altogether.


Testing the Obvious

Sometimes, the diagnosis is clear to the clinician from the start. And the thing is…licensed clinicians aren’t required to do testing to support a diagnosis. For example, you don’t need any psychological testing to find out if someone has anxiety. Just ask them! If the situation is pretty clear, it may be a waste of money and time to go through the process. However, even when the diagnosis is obvious, some “powers that be” require formal testing in order to justify providing certain prescriptions, considering accommodations, determining educational placement, etc.


There are a few situations in which I would highly recommend neuropsychological/psychological testing:

  • Suspicions of Attention Deficit Disorder or Autism Spectrum Disorder

  • Concerns about learning disabilities such as dyslexia, dyscalculia, visual/motor deficits, auditory or visual processing issues, etc.

  • Memory problems/loss, unexplained changes in consciousness, sudden changes in personality

  • Getting a baseline BEFORE you have problems so you can compare the testing at a later time

  • When you disagree with your current diagnosis

So, what are some limitations to psychological testing?

  • The results of the test are only as good as the test itself.

  • Self-report measures are biased but are frequently used

  • The tests often rely on agreed-upon constructs (such as the word “personality”) rather than on concrete data (such as red blood cell count). This leaves them open to error if the construct itself is problematic.

  • The test was developed to be used with a specific population. If the examinee is different in any way, this could make the results invalid.


  • There is no definitive test that can determine a diagnosis.

  • The results of the test reflect only a snapshot in time. The examinee may test differently on another day or in another situation.

  • The results of the test are only as good as the clinician who is giving them. Some tests are highly sensitive to the training of the examiner. Bad data in = bad data out.

  • Even if the test results support a particular diagnosis, the clinician can disagree.

Here’s the bottom line: There is no psychological or neuropsychological test that can tell anyone definitively that they have ANY diagnosis. It actually requires that a trained, qualified clinician combine their opinion of the test results with a full diagnostic interview AND the test results. And guess what? Take a random sample of 10 clinicians and I’ll bet you a back tooth (southern saying) that maybe 3 of them would agree. Maybe. Why?

Well…maybe you’re familiar with the expression about what opinions are like ;)