Special Interest Topic 5.1

Are Psychological Tests as Accurate as Medical Tests?

In my last post, I wrote about the potential relationship between procrastination and stress. I had planned to continue with this general theme, but then I stumbled across Special Interest Topic 5.1.

Special Interest Topic 5.1, of our oh-so-lovely-yet-spectacularly-dry-textbook, explores (what I believed to be) the long-held assumption that medical tests are more reliable and more valid than psychological tests.

The conclusion was that they aren't.

Interesting.

Now, as a student in a class about psychological testing who happens to have two physicians for parents, I was (perhaps not surprisingly) a little curious about the strength of this claim. So I did some digging. The remainder of this post highlights what I was able to come up with.

In 2001, a report (Meyer et al., 2001) was commissioned by the American Psychological Association to assess the claim mentioned above: that the validity of data provided by psychological assessments is comparable to that of medical tests. By measuring and reporting on the effect sizes for more than 140 medical and psychological tests (in statistics, an effect size is a quantitative measure of the strength of a phenomenon; thus, a larger effect size indicates greater validity) Meyer et al. arrived at the following conclusions:

1. Psychological test validity is strong and compelling.
2. Psychological test validity is comparable to medical test validity.
3. Distinct assessment methods provide unique sources of information.
4. Clinicians who rely exclusively on interviews are prone to incomplete understandings.

Again, interesting. At this point it’s looking pretty good for psychological tests. But are these conclusions themselves (number 2, in particular) actually valid?

Not everyone seems to think so…

Howard Garb and crew (Garb et al., 2002) conclude that Meyer and his buddies did not actually establish that psychological test validity is comparable to medical test validity, accusing ol’ Mr. Meyer of reporting misleading effect sizes. Although it may appear that Meyer et al. correctly summarized the results of their meta-analyses, in some cases they seem to have calculated their own effect sizes, in turn making their review of the literature unreliable and extremely difficult to interpret. Garb et al. even go as far as saying that “science should not be sacrificed for the sake of guild interests,” referring of course to the potential benefits of portraying medical tests and psychological test as being equally valid. Yikes.

Yikes, indeed.

So what should the concerned reader make of all this? Should you ask your doc for the MRI or the neurocognitive assessment? Fortunately, both sets of authors seem to agree that the appropriateness and validity of a test depends on a number of factors. Thus psychological and medical tests are each capable of providing unique benefits, with these benefits varying depending how far along you are on the continuum of care. So while conflicting reports such as these may make it tempting to demand “all the tests,” for now, it’s probably best to leave these decisions in the hands of your healthcare professional, rather than with some guy writing a blog on the internet.

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References:

Comparison of medical and psychological tests. Garb, Howard N.; Klein, Donald F.; Grove, William M. American Psychologist, Vol 57(2), Feb 2002, 137- 138. http://dx.doi.org.proxy2.library.mcgill.ca/10.1037/0003-066X.57.2.137

Psychological testing and psychological assessment: A review of evidence and issues. Meyer, Gregory J.; Finn, Stephen E.; Eyde, Lorraine D.; Kay, Gary G.;Moreland, Kevin L.; Dies, Robert R.; Eisman, Elena J.; Kubiszyn, Tom W.; Reed, Geoffrey M. American Psychologist, Vol 56(2), Feb 2001, 128–165. http://dx.doi.org.proxy2.library.mcgill.ca/10.1037/0003-066X.56.2.128