Comparison of short and long versions of the Prudhoe Cognitive Function Test and the K-BIT in participants with intellectual impairment.

Researchers gave the adults with intellectual disability two IQ tests. One test was the full Prudhoe Cognitive Function Test. The other was the K-BIT.

They also tried two shorter versions of the Prudhoe test. Each short form took half the time to give.

The team wanted to know if the short forms gave the same results as the full test.

All three Prudhoe versions matched the K-BIT almost perfectly. Scores lined up at r = .90 or higher.

The short forms worked just as well as the long form. You can swap them without losing accuracy.

Poppes et al. (2010) looked at executive-function tests in the same group. They found the BADS-C often bottomed out at zero scores. The Prudhoe short forms avoid that floor-effect problem.

Drijver et al. (2025) created a new adaptive-behavior tool called DIAB. Like the Prudhoe study, DIAB showed strong validity for adults with moderate to profound ID. Both papers give you reliable shortcuts for busy clinics.

Romanowich et al. (2010) and Poppes et al. (2010) found that executive function, not IQ, drives decision-making tasks. This means the Prudhoe test gives you a quick IQ estimate, but you still need to check executive skills separately when planning supports.

You can now save 15–20 minutes per client by using a Prudhoe short form. The score will still line up with the K-BIT. Use the extra time to probe executive skills or adaptive behavior instead of giving a longer IQ test.