Heritability and Longitudinal Stability of Planning and Behavioral Disinhibition Based on the Porteus Maze Test

The Porteus Maze Test (PMT) provides measures of planning and behavioral disinhibition. The PMT was administered to 941 twins during Wave 1 (9-10 years) and 320 twins during Wave 2 (11-13 years). Participants were drawn from the University of Southern California Risk Factors for Antisocial Behavior Study (RFAB). Heritability of behavioral disinhibition, determined by PMT Q-Score, were 33% at Wave 1 and 52% at Wave 2. For planning, determined by Test Age, heritability was 53% at Wave 1; at Wave 2, the non-shared environment was important in boys, whereas genetic influences were important in girls. Both indices were modestly stable (r = 0.52; r = 0.37). A common genetic factor influenced both indices, respectively, at the two time points, with no 'new' genetic variance at Wave 2; the non-shared environment was time-specific. Thus, both genetic and non-shared environmental influences are important for behavioral disinhibition (Q-Score) and planning (Test Age).