Succumb to habit: Behavioral evidence for overreliance on habit learning in Internet addicts

Studies of Internet addiction (IA) under the cognitive-behavioral framework have suggested that IA derived from the excessive expectation of positive outcomes, which was a goal-directed behavioral progress. However, according to the dual-system account under the framework of associative learning theory, IA should be considered as a transition process from goal-directed to habit-based. It can be explained in terms of aberrant learning processes, where Internet addicts apparently succumb to habit with decreased sensitivity to reward devaluation. To test this hypothesis, we implemented an instrumental learning paradigm to investigate the difference of reliance on habit between Internet addicts and non-addicts. A total of 21 Internet addicts and 23 normal control subjects were trained in the first experimental phase and learned to associate stimuli with rewarding outcomes by pressing correct keys. In the subsequent outcome devaluation test and in the stimulus-response (S-R) habit test, subjects were required to adjust responses to changes in the value of current outcomes. Results revealed that (1) all subjects were able to gradually acquire the correct behavioral responses in the training phase, however, (2) extensive training rendered Internet addicts less sensitive to outcome devaluation in the outcome devaluation test, and (3) Internet addicts insisted on responding to previous stimuli in the S-R habit test, regardless of whether their responses were rewarded. Thus, we conclude that Internet addicts have an enhanced propensity to develop stimulus-driven habits and overly rely on it, leading to the failures to adjust behavior during goal reevaluation.