Less Efficiency in Execution and Observation, but Not Imitation, of Actions in High-Functioning Young Adults with an Autism Spectrum Disorder

Background:  Autism spectrum disorders (ASDs) are often accompanied by problems in planning and execution of goal-directed actions. The concept of planning movements in order to attain comfort at completion, though sacrificing initial comfort, is known as end-state comfort (ESC) (Rosenbaum et al., 1990). Hence, the application of ESC points to efficient action planning. The bar-transport paradigm is a simple, but very effective measurement tool for providing valuable information on the application of ESC and the efficiency of a persons’ motor planning skills (Rosenbaum et al. (1990). Several studies suggest that persons with ASD are impaired in the spontaneous application of ESC (Hughes, 1996; Conson, et al. 2013, Gonzalez et al., 2014), but not when they are allowed to imitate this application (Hamilton, Brindley & Frith, 2007; Jiménez, Lorda, & Méndez, 2014). To the best of our knowledge, there are no studies which have investigated the understanding and prediction of efficient goal-directed actions applying ESC. 

Objectives:  The present study investigated the efficiency of goal-directed actions in the domains of action execution, imitation and prediction in young adults with an ASD compared to typically developing peers. 

Methods:  A cross-sectional study was conducted containing 21 persons with ASD and 26 typically developing persons (TDP) between 17 and 29 years of age. In the first experiment, action efficiency was investigated by analyzing the spontaneously application and imitation of ESC in addition with speed and timing of actions. In the second experiment, the prediction of efficient actions was studied.

Results:  

Experiment 1 showed that participants with ASD were less able to spontaneously perform efficient actions compared to TDP (U = 98.5; Z = -2.14; p = .03). Results of a mixed model analysis with group, trial and their interaction as fixed factors and individual participants as random factor showed that the timing ranging from stimulus onset to action start (F1,35 = 2.2; p = .14) and from action start to lifting the bar (F1,35 = 3.2; p = .08) did not differ between both groups. In contrast, participants with ASD were significantly slower than TDP in the executive part (F1,35 = 5.2; p = .03; β0 ASD = .91; β0 TDP =.91-.04; β1 = -.005). This was no longer true when their actions were visually guided online in the imitation condition (F1,34 = .03; p = .86; F1,34 = .5; p = .47; and F1,34 = 2.9; p = .10, respectively). Furthermore, in this condition both groups did not differ in their application of ESC when imitating the actions (U = 149.5; Z = -.35; p = .72).
Experiment 2 showed that participants with ASD were less able to predict ESC when they observe efficient actions compared to TDP (U = 177.5; Z = -2.06; p = .04). In contrast, according to mixed model analysis both groups did not differ in their reaction times towards observed actions (F1,45 = 1.5; p = .23).

Conclusions:  Persons with ASD were less able to spontaneously execute and predict efficient actions, although they were able to imitate them.