Planning and Efficiency on the Tower of London Test in ASD

Background: Planning is a critical component of executive functioning that facilitates the proper execution of goal-directed behavior. Deficits in executive functioning can underlie many of the challenges faced by individuals with autism spectrum disorder (ASD), and many studies show that individuals with ASD exhibit poor planning compared to neurotypical (NT) individuals.

Objectives: To investigate the effect of ASD on planning ability in adults.

Methods: Participants were recruited through the community and underwent screening for ASD prior to cognitive assessments. Inclusion/exclusion criteria included IQ > 80, male, and general good health. NT participants (n = 38, age 18-64, M = 38, SD = 15.24) were age- and IQ-matched to individuals in the ASD group (n = 52, age 18-70, M = 38, SD = 17). Participants performed a Tower of London test, a commonly used neuropsychological test requiring planning. The test requires participants to arrange beads on pegs in specified patterns in as few moves as possible, where consecutive trials get progressively more difficult. Total moves, initiation time (time spent planning), execution time, and total number of correct trials (completed without making extra moves) was recorded. SPSS (v19) was used to test mean differences between ASD and NT groups, and linear regression modeling was conducted to test the relationship between initiation time and number of trials completed correctly for each group.

Results: NT subjects completed significantly more correct trials than did their ASD counterparts, and the ASD group made significantly more moves across all trials. The two groups did not show significant differences in the amount of time they used to plan moves. However, linear regression revealed that there was a significant and negative relationship between planning time and total move count for the ASD group, but not for the NT group. Thus, for individuals with ASD, more time spent planning moves resulted in the making of fewer unnecessary moves.

Conclusions: Compared to healthy controls, adults with ASD displayed deficits in planning on a Tower of London task. While both ASD and NT groups showed similar variability in time spent planning, planning time was an important determinant of correctly completing the task for only the ASD group. In summary the study indicates that though some individuals with ASD had difficulty in motor planning, those who utilized longer planning periods had the best performance. NT individuals completed the task with more ease than did the ASD individuals, with little to no benefit from longer planning periods. Since no instruction was given regarding using planning as a strategy, it is difficult to know whether the use of planning was incidental or deliberate. This study suggests that increased emphasis on planning may improve some aspects of executive functioning in individuals with ASD.