Relapse has been a great challenge in clinical treatment and experimental studies of drug addiction. Recent studies suggest that psychological dependence may play a major role in addiction relapse, even more important than physiological dependence. Then a fundamental question arises: how to measure the psychological dependence?
How to examine whether an addict has psychologically quitted when leaving drug rehabilitation centers? Self-report, a commonly used evaluation approach, is inevitably vulnerable to various cognitive influences, particularly in explicit tasks. Therefore, an objective index is necessary to evaluate the subliminal psychological drug dependence level. The objective of the current study was to develop such a psychological paradigm to probe the unaware attentional bias of in smoking addicts. Experiment 1 adapted the interocular suppression technique of binocular rivalry to study the attentional bias to cigarette pictures in smokers and age-matched nonsmoker. Results show that the smokers demonstrated similar attentional bias in both visible and unaware conditions, while non-smokers showed attentional bias only in the visible condition, and there was a significant interaction between experiment conditions and subject groups. These results provide compelling evidence for addiction-specific attentional bias in cigarette smokers, by minimizing the influence of confounding conscious factors. Furthermore, attentional bias of smokers in unawareness state was negatively correlated with their cigarette dependence levels, while their pre-test cigarette craving levels was positively correlated with their attnetional bias in the visible condition. This pair of correlations further demonstrated the advantages of unawareness state in disclosing stable dependence states, therefore supporting the effectiveness of the paradigm used in this study.
Another interesting finding of Experiment 1 is that non-smokers also showed attentional bias in the visible condition. To exclude the possibility that the attentional bias found in experiment 1 was task-specific, experiment 2 adapted the most commonly-used visual dot probe task with smoking scenes as in relevant reference. The result in experiment 1 was well replicated, i.e., nonsmokers in experiment 2 also showed significant attentional bias to smoking-related stimuli, We interpenetrate this interesting finding as an effect of environmental influence, as the participants of the current study live in a highly smoking-exposed and smoking-encouraged environment, which is quite different with the participants of studies reported in the literature. A series of questionnaires and scales administered in the current study indeed show that most smokers smoked due to influence of the environment. They also acknowledged that smoking as an important media of social communication in China, and even considered that away from the smoking environment would effectively help them to quit. The current study also found that the disgust level towards cigarette pictures and smoking-related scenes of non-smokers was positively correlated with their attnentional bias in the visible condition of experiment 1. It is likely that in a highly smoking-encouraged environment, the remaining few on-smokers have severe disgust to cigarettes and smoking scenes; and their attentional bias might be caused by disgust avoidance.
In conclusion, the current study represents the first study showing the existence of unaware attentional bias to smoking related stimuli in cigarette smokers by applying the interocular suppression paradigm, providing a reference to study of dependence of other drugs. The current study also found that our non-smoking participants also showed attentional bias to smoking related stimuli, which may be due to the possible influence of highly smoking-exposed environment of our participants.