Effects of Mutilation Images on Self-Control Behavior and Delay Discounting

Flora et al. (1992) found that intense noise increased impulsive responses during a task in which college students chose between smaller-sooner (SS) and larger-later (LL) options to earn points exchangeable for money (SS – impulsive option; LL – self-control option). Furthermore, the removal of the aversive noise did not result in increments in LL responses, and vice versa (i.e., self-control preference continued when the noise was later introduced). Considering human physiological responses to pictures of human mutilation resemble those produced by aversive stimuli (e.g., heart rate changes), we explored if the disruptive effects of aversive stimuli on self-control behavior could be reproduced with images of mutilation. Matching-to-sample trials depicting the images of mutilation were interspersed between the choice trials with different probabilities (Random-Time 0 s, 20 s, and 30 s). A delay-discounting task was introduced before and after the choice task to obtain k and Area Under the Curve (AUC) values, which were used to explore a relationship with performance during the choice task. A within-subjects design with 24 participants was implemented. Each probability of matching mutilation images was an experimental condition. Initial exposure to high probability of matching overall produced indifference (~ 50% LL responses). Proportion of LL responses increased when the probability of the images was reduced. Participants not initially exposed to the images developed preference for the self-control option and maintained it during subsequent conditions when probability of matching images changed. Delay-discounting measures were not related to performance during the choice task, possibly because of a magnitude effect (smaller reinforcers are discounted more steeply than larger reinforcers). Future studies must address the divergent results in this line of research, especially the fact that noise and visual stimulation produced mostly indifference, whereas cold water (Flora et al., 2003) is the only stimulus that has been shown to increase impulsive choice beyond indifference.