We appreciate the interest in our article1 shown by Robertson et al. While the age at assessment with the Bayley-III differed between our study1 (24-month corrected age) and that of Robertson et al (18-month corrected age), their small study supports our conclusion that the new Bayley-III underestimates developmental delay, at least for the cognitive domain. The strength of the Robertson et al study is that both the BSID-II and Bayley-III were administered to their sample of 40 extremely preterm children. Based on the BSID-II, 20% of their sample had moderate to severe cognitive delay, a rate consistent with the extensive literature on this at-risk population. In contrast, with the Bayley-III, no child exhibited moderate to severe cognitive delay but 18% exhibited language delay.
Anderson PJ, De Luca CR, Hutchinson E, Roberts G, Doyle LW. Application of the Flynn Effect for the Bayley III Scales—Reply. Arch Pediatr Adolesc Med. 2010;164(11):1072-1073. doi:10.1001/archpediatrics.2010.200