Abstract
Reinforcement learning relies on the reward prediction error (RPE) signals conveyed by the midbrain dopamine system. Previous studies showed that dopamine plays an important role in both positive and negative reinforcement. However, whether various reinforcement processes will induce distinct learning signals is still unclear. In a probabilistic learning task, we examined RPE signals in different reinforcement types using an electrophysiology index, namely, the feedback-related negativity (FRN). Ninety-four participants were randomly assigned into four groups: base (no money incentive), positive reinforcement (presentation of money rewards), negative reinforcement (removal of money losses), and combined reinforcement (money rewards and removal of money losses) groups. In addition, in order to evaluate the engagement of emotional activity in the different reinforcement processes, Positive and Negative Affect Schedule-Expanded Form (PANAS-X) scales were applied before and after the experiment to detect the emotional changes. The results showed that there was no difference between groups in the dopamine-related learning bias. However, compared to the other three groups, negative reinforcement elicited smaller FRN (the difference-wave measure) during the learning, stronger positive affect and joviality, and less fatigue after the learning, in which the difference between the negative and positive reinforcement groups was smaller. The results indicated that pure avoidance motivation may induce distinct emotional fluctuations, which influence the feedback processing.
Highlights
Reinforcement learning is guided by the computation of reward prediction errors [RPEs (Sutton and Barto, 1998)], i.e., the difference between actual outcomes and expectations, which is suggested to be achieved by the midbrain dopamine system (Schultz et al, 1997; Schultz, 1998)
The first goal of the present study was to investigate whether reinforcement type will modulate the feedback-related negativity (FRN) and the positive vs. negative learning bias, both of which are suggested to be related to the activity of the midbrain dopamine system
Our study provided the first investigation to directly compare the learning bias, the emotional reactions, and the FRN in four reinforcement types in separate groups, namely, positive, negative, and combined reinforcement, as well as a control condition with no money incentive
Summary
Reinforcement learning is guided by the computation of reward prediction errors [RPEs (Sutton and Barto, 1998)], i.e., the difference between actual outcomes and expectations, which is suggested to be achieved by the midbrain dopamine system (Schultz et al, 1997; Schultz, 1998). Positive RPEs (outcomes are better than expectations) signaled by the phasic dopamine firing facilitate the selection of actions, whereas negative RPEs (outcomes are worse than expectations) by the dopamine dips inhibit it (Frank, 2005). Both the presentation of rewards (positive reinforcement). It was suggested that the dopamine release is more complicated in negative reinforcement (Wenzel et al, 2015) The investigation of this issue helps to characterize the potential effects of appetitive and aversive stimuli, as well as provide evidence to solve the debate about positive and negative reinforcement (Michale, 1975; Baron and Galizio, 2005, 2006; Chase, 2006; Iwata, 2006; Johnston, 2006; Lattal and Lattal, 2006; Sidman, 2006)
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