Out of all the subtests I have added to the PAIS, perhaps none were harder to construct than the multiple choice test Pieces. I wanted at least one subtest that measured pure spatial reasoning. I had already added cubes, however cubes is kind of a hybrid of spatial and working memory. Pieces was inspired by the Object Assembly subtest in the early versions of the Wechsler, which itself was inspired by the feature profile test used to screen out low IQ immigrants at Ellis island. However unlike these tests, you don’t actually put anything together in Pieces, you just answer 21 questions in 20 minutes about how you would do so which makes the test much more difficult and reliable though perhaps less fun and clinically informative.

Is the above picture not just the coolest thing you’ve ever seen in your life? I love old school psychometrics.

A much more detailed cardboard version of this profile puzzle would appear on the WAIS-III, WAIS-R, original WAIS and the granddaddy of all Wechsler scales: the ancient WBI, reminding us once again that Wechsler, who ironically was an immigrant himself, invented almost nothing. His genius was not creation, but curation. His tests became so popular because he did a brilliant job selecting his original 11 subtests and he did so based not exclusively on psychometrical criteria, but on his own intuition of what it meant to be an intelligent adult in 20th century America, which he defined as one who knows and understands the World around them, and has the resourcefulness to cope with its challenges. For Wechsler, clinical psychology was as much art as science and these old school hands on performance tests really measured if you could adapt to your environment in a creative way.

But their Achilles’ heel was low reliability which is probably caused by the luck factor of randomly fitting pieces together. It was also inconvenient to psychologists to lay out all the puzzle pieces in just the right position, so shortly after Wechsler died, newer WAIS revisions discontinued the subtest.