Keolu lies. One of the researchers of the Perry study responded to a critical review of their research in an addendum to the review. The editors which published probably insisted that the response be added for professional clarity.

http://www.welfareacademy.org/pubs/early_education/pdfs/Besharov_ECE%20assessments_Perry_Preschool.pdf

 "While fair criticism is essential to the scientific method and the advancement of
knowledge, unfair criticism undermines the scientific method and presents unhelpful information masquerading as knowledge....  We do appreciate the opportunity to respond to these criticisms, however, particularly those that Besharov and his colleagues repeat from other sources to which we have never directly replied. In a good story that may even be true, B. F. Skinner is said to have retorted to a persistent questioner, “Science progresses by standing on the shoulders of those who have gone before. But you sir, are standing on my feet.”