Timing of brain damage and verbal-performance IQ tilts.

Sir, Anderson et al. (2009) refuted the Kennard Principle, which states that the immature brain is more plastic and less vulnerable to insult than a mature brain (Montour-Proulx et al., 2004); however, there are important errors in Table 5 of their paper. The IQ data for their six age subgroups do not tally with the total group figures in the last column of Table 5. In each of these six subgroups, the IQ figure in the last row is intermediate between the first two rows, so clearly must be the full scale IQ, and not performance IQ as stated (V, P and FS refer to verbal, performance and full scale IQs on the Wechsler Intelligence Scales). One would then assume, as is usually reported, that the first subgroup row is verbal IQ, the second performance IQ and the third full scale IQ. However, there are two major problems with this reading: