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"You can't fake good"

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I've been saying this for some time about varying IQ scores for murder defendants, but it's good to read of a credentialed expert actually testifying in court in those words.

The IQ test is a performance test, and it depends for its validity on the subject doing his best.  A person who wants to lower his score can do so by intentionally choosing a wrong answer or even by simply slowing down.  On the other hand, aside from cheating, there is no way to intentionally alter one's score upward. 

Tom Hanks can play Forrest Gump.  Forrest Gump could never play Tom Hanks.

How fast can you run a mile?  If you have various times, and there hasn't been any material change in your condition between them, the fastest time is the time in which you can run a mile.  The slower times probably represent occasions when you were not motivated to do your best.

From a variety of IQ scores, therefore, the high scores are more likely than the low scores to represent a person's true intelligence, particularly if the low scores are made in a context where the person has a incentive to malinger.

Today's News Scan links to this story about Pennsylvania torture killer Ricky Smymes.

[Dr. Leigh D.] Hagan and Dr. Bruce Wright, the psychology department chairman at St. Clair Hospital in Mt. Lebanon, told jurors that Smyrnes scored 81 on two IQ scores when he was an 8-year-old. "You can't fake good," Hagan testified.
Hagan told jurors he was hired as an expert in the Virginia murder case of Daryl Atkins, in which he was initially sentenced to death.
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Dr. Alice Applegate, the defense's mental health expert, testified that if an IQ falls in the range of 70-75, that person is "mildly mentally retarded."
Um, no.  The DSM-IV says mild mental retardation is "IQ level 50-55 to approximately 70."  Because the test has a margin of error of 5, it is possible for a person testing up to 75 to have a real IQ of 70 and thus be retarded, but possible doesn't cut it.  A person testing above 70 is more likely not retarded than retarded, and that is the question for a categorical exemption from the death penalty.  (Borderline intellectual functioning, the next step up, can of course be considered as a circumstance in mitigation.)

Smyrnes has several scores below 70, including a 60 on a test taken last year, [Applegate] testified.
That is after he was arrested for the present crime and had a powerful incentive to malinger.

"His claim that he was mentally retarded first appeared after he was incarcerated for this event," Wright told jurors.

Wright said mental health evaluations of Smyrnes, conducted when he was between the ages of 4 and 19 at various treatment facilities and schools, never identified him as mentally challenged.
BTW, the Language Police have decided that "mentally retarded" is now verboten, even though it is a perfectly good term, it is the term in the DSM-IV, and it was the preferred term for many years.  So people who actually care what the Language Police think (not including yours truly) use alternative but wrong terms such as "mentally disabled" or "mentally challenged."  Those mushy terms do not mean the same thing, and it is not correct to substitute them for a term with a precise, clinical meaning.

The DSM-V will use the term "intellectually disabled," so that is an acceptable and correct substitute.

2 Comments

Malingering should forfeit all appeals.

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