关键词: 跨期决策, 隐藏的0效应, 毒品成瘾

Abstract: Deficiency of intertemporal decision-making in substance addicts which was considered as the behavioral marker of this population has been confirmed by abundant of researches. Besides, more and more results from longitudinal studies indicated that deficiency of intertemporal decision-making in substance addicts may play a significant role both during the beginning, development, withdrawal and prognosis phases in addiction. It followed by a number of researches focused on how to improve the intertemporal decision-making in substance addicts. Among the traditional ways which aimed at this improving, only episodic future thinking (EFT) showed consistent results. However, EFT deeply depends on the active efforts from addicts to think of some cues about future. Because of this kind of demanding, the actual improving effects from EFT is limited for this population. Out of the area of studies in addiction, researchers have found that the intertemporal decision-making could be improved by only explicating the potential opportunity cost of both sooner but smaller (SS) reward option and larger but longer (LL) reward option, this phenomenon was called hidden-zero effect. In order to verify whether the deficiency of intertemporal decision-making in substance addicts could be improved by explicating the potential opportunity cost of both options in intertemporal decision-making, two experiments were designed. Experiment 1 employed the monetary intertemporal decision-making task, and 30 male heroin abstainers were recruited. The result showed that compared with the hidden-zero condition in which the opportunity cost of both options in intertemporal decision-making were not explicated, the number of SS chosen by these male heroin abstainers was significantly lower in explicit-zero condition in which the opportunity cost of both options in intertemporal decision-making were explicated. Experiment 2 employed the cross-commodity delay discounting task which use heroin as immediate reward option and money as delayed reward option, and 27 male heroin abstainers were recruited. The result showed that the delay discounting levels indicated by area under curve (AUC) of these male heroin abstainers were not significantly different between explicit-zero condition and hidden-zero condition. Explicating the potential opportunity cost of both options in intertemporal decision-making may extended the temporal horizon of heroin abstainers and augmented their far-sighted system of intertemporal decision-making, so they could pay more attention to the high reward value of LL which may be less noticed in hidden-zero condition. The relative subjective reward value of SS may decrease when the reward value of LL was more considered. Finally it led to the less number of SS chosen by these male heroin abstainers in Experiment 1. However, considering the relatively higher subjective reward value of heroin compared to money for these heroin abstainers, the relative subjective reward value of immediate heroin reward maybe less changed by explicating the potential opportunity cost of both options in intertemporal decision-making. Because of this, the delay discounting levels in explicit-zero condition and hidden-zero condition were not significantly different in Experiment 2. In conclusion, explicating the potential opportunity cost of both options in intertemporal decision-making can improve monetary intertemporal decision-making instead of cross-commodity intertemporal decision-making for male heroin abstainers.

Key words: intertemporal decision-making, hidden-zero effect, drug addiction