As was found at younger ages, children who had externalizing problems in mid- to late-elementary school were clearly predicted by deficits in their attentional and inhibitory EC, as well as their high impulsivity, when compared with control children and especially children with pure internalizing problems. This pattern of association of externalizing with high impulsivity was fairly strong and was somewhat more evident in regard to pure externalizing (EXT) than co-occurring externalizing (CO) problems. Such a pattern would be expected if children with internalizing problems are often overcontrolled rather than impulsive: Their overcontrol might counter their impulsive tendencies. The findings are also consistent with Stieben et al.’s (2007) suggestion, based on electroencephalography (EEG) findings, that children with co-occurring problems have a more anxious regulatory style than children with solely externalizing problems. Thus, for children with co-occurring internalizing and externalizing problems, the more inhibited pattern of responding that is characteristic of internalizing children may partly buffer children from the problematic behavioral tendencies associated with externalizing problems.
