“…All of these tests but the WAIS are designed to screen and detect deficits in patients. However, normative studies focused on these tests show inter-individual variability in healthy subjects’ performances with a relative standard deviation (i.e., rSD = standard deviation/mean) of 4–12% in the PPT test ( Howard and Patterson, 1992 ; Rami et al, 2008 ; Klein and Buchanan, 2009 ; Gamboz et al, 2009 ; Callahan et al, 2010 ), an rSD of 25–45% in the similarities subtest of the WAIS ( Wechsler, 2008 ; Wisdom et al, 2012 ; Harrison et al, 2014 ), an rSD of 20–40% in the D-KEFS sorting test ( Delis et al, 2001 ; Homack et al, 2005 ; Mattioli et al, 2014 ), and an rSD of 20%–60% in the number of categories found in the WCST ( Caffarra et al, 2004 ; Shan et al, 2008 ; Arango-Lasprilla et al, 2015 ). Whether this inter-individual variability in categorization tasks is related to variability in brain structure remains unknown.…”