MAIN EFFECTS OR TRANSACTIONS IN THE NEUROPSYCHOLOGY OF CONDUCT DISORDER - THE NEUROPSYCHOLOGY OF CONDUCT DISORDER - COMMENTARY

In this commentary, we (a) discuss logical and empirical limits on the transactional model in accounting for the etiology of any development al psychopathology, including conduct disorder (CD), and (b) review ev idence bearing on whether or not frontal lobe lesions can directly pro duce CD behavior. Logically, transactions can both decrease and increa se phenotypic variance; moreover, there is a mathematical limit (50%) to the amount of variance for which they can account. Empirically, doc umenting a transactional effect requires (a) that we have unconfounded measures of a child's biotype and social environment, (b) that the bi otype and social environment are correlated, and (c) that we have a de sign (such as an adoption design) that is capable of separating the co ntribution of this correlation to outcome variance from the main effec ts of either biotype or social environment considered separately. Give n these limits, we should also look for main effects in the etiology o f CD. We argue that early damage or dysfunction in the frontal lobes m ay be one such plausible main effect on CD.