Preserved Socio-Economic Decision Making in Autism Spectrum Disorder: Evidence from the Ultimatum Game

Background: Game theoretical tasks have contributed significantly to our understanding of the role of intuitive and more deliberative reasoning processes in social decision making. One of these tasks is the Ultimatum Game (UG; Fehr & Schmidt, 2006), in which a proposer can decide how to split a given amount of money (£10) between themselves and a responder who then has the opportunity to either reject or accept the offered amount. If the responder accepts, the money is paid out as proposed; if s/he rejects neither participant receives any amount. The UG reliably demonstrates that social-economic decisions are primarily governed by relatively intuitive pro-social motives rather than rational thought. Thus, proposers commonly offer equal shares and responders tend to reject offers below 30%, when it would be rational for the proposer to offer the minimum amount possible under the assumption that a rational responder would accept something over nothing (Fehr & Schmidt, 2000). The difficulties that individuals with ASD demonstrate in various aspects of social cognition, coupled with their relative strengths in rule-governed and analytical thinking, would lead to the prediction that decisions on the UG by individuals with ASD would be based relatively more on deliberative thought than social-emotional intuition.

Objectives: To test the above prediction by examining the effects of time pressure on decision making in ASD on standard and modified versions of the UG that require either a standard reject/accept decision of offers or a calculation of whether more or less than 30% has been offered.

Methods: 23 ASD and 23 age and ability matched TD adults completed a multi-trail UG in which 48 offers were presented that varied across four levels of fairness (50%, 40%, 25% or 20% of varyingly sized pots). On two blocks participants needed to make standard accept/reject decisions, either under a 1.5 second time limit or no time-limit. On another two blocks, participants needed to indicate whether they were offered more or less than 30% of the total pot, again either under time pressure or not. Finally, participants completed the cognitive reflection task (CRT; Frederick, 2005), which provides a measure of how likely people are to override instinctual responses with reflective thought.

Results: A significant Task x Time pressure interaction showed that time pressure significantly impacted on participants’ ability to indicate whether offers were more or less than 30% without any significant effects on rejection rates. The absence of any group differences, suggests that both individuals with and without ASD reject offers more on the basis of an instinctual reaction rather than a rational calculation, which was further supported by inverse correlations between rejection rates and CRT even when overall accuracy on the mathematical calculation task was statistically controlled.

Conclusions: Contrary to predictions, the results suggest that individuals with and without ASD rely on similar intuitive, rather than deliberative processes to formulate decisions in the UG. The results will be discussed in light of additional evidence which suggests few differences in how individuals with and without ASD form decisions on the UG.