Despite many years of research on cognitive conflicts, the potential role of emotions or affects in these situations is taken into account only recently. The present study investigates the effect of reward-induced motivational states on one element of cognitive control during conflict processing – action monitoring. Monitoring one’s own actions is a critical precondition for adaptive behavior in general and for handling cognitive conflicts in particular.
The original conflict monitoring account (Botvinick et al., 2001
) postulated that the dorsal anterior cingulate cortex (ACC) responds to conflicts, arising during various tasks, by issuing a conflict signal. This conflict signal triggers strategic adjustments in cognitive control by redirecting attention according to the task demands. Thus, the ACC would serve as a conflict monitoring device. The conflict monitoring theory stimulated research interests in sequential dependencies during conflict processing. In typical interference tasks like the Stroop, Flanker, or Simon task, a set of multidimensional stimuli is assigned to a set of responses. Usually, only one stimulus dimension is task-relevant, while other stimulus dimensions are task-irrelevant but at least one of them shares features with the relevant dimension (Lu and Proctor, 1995
). In the Simon task, for example, left or right-hand responses are performed as a function of a non-spatial stimulus feature (S; e.g., shape or color) while the stimuli are presented either on the left or right-side. Responses (R) are faster and more accurate when S and R locations correspond (C, compatible events) than when they do not correspond (IC, incompatible events). In general, incompatible trials provoke conflicts in information processing when at least one feature of S or R contradicts the correct response. For example, in the Simon task, the stimulus may activate a right-side response by virtue of its (irrelevant) location, which contradicts a left-side response demanded by the relevant stimulus dimension, resulting in slower and more error-prone responses.
In most kinds of tasks with S–R conflicts, conflict-strength in the current trials depends on the correspondence condition of the preceding trials: after non-corresponding events conflicts are much smaller than after corresponding events (Gratton et al., 1992
; Stürmer et al., 2002
; Egner et al., 2007
). According to the conflict monitoring approach, conflicts redirect the attentional focus to task-relevant features, diminishing the influence of task-irrelevant features, hence reducing the conflicts between these features and the response on the next trial.
In a recent extension of his conflict monitoring account, Botvinick (2007
) suggested that the processing of conflicts is effortful and therefore aversive. Hence, conflicts should bias decision-making toward more efficient task strategies. The presumable redirection of attention after a conflict trial may be a direct consequence of the aversive efforts in dealing with this conflict. If conflict adaptation behavior is triggered by the negative affect elicited by conflicts, one may presume that positive affect would counteract conflict adaptation. This assumption is supported by findings of Kuhl and Kazen (1999
), showing that the Stroop effect is largely reduced by the short-term induction of positive affect. Following the suggestion that conflicts are experienced as negative, van Steenbergen et al. (2009
) reasoned that monetary gain and its positive emotional consequences might counteract the aversive quality of the preceding conflict and hence reduce subsequent conflict-driven adaptation processes. Indeed, in a flanker task a small but significant reduction of conflict adaptation was found after monetary gain. In a follow-up study, van Steenbergen et al. (2010
) applied mood induction and showed that as a trendless positive mood induction tended to be associated with larger conflict-related adaptation. Taken together, the authors concluded that affect adaptively regulates cognitive control.
A direct link between affective and cognitive processing in conflict control was already implied in the seminal model by Miller and Cohen (2001
). In this account, the prefrontal cortex (PFC) establishes S–R mappings by biasing competition between conflicting sensory inputs or motor outputs to favor relevant aspects for current task-performance. Phasic dopamine (DA) release by the midbrain DA system plays a major role in gating the appropriate update of task-relevant goal representations in the PFC. Thus, reward-driven DA release related to the reward prediction error (Schultz, 1998
) is proposed to strengthen top-down control over bottom-up processing. One could therefore assume that conflict adaptation as a top-down control process should be enhanced after a reward when DA is released.
This assumption is in line with studies investigating conflict adaptation in Parkinson’s disease (PD) patients who suffer from a low level of midbrain DA. Conflict adaptation in a Simon interference task was much reduced in PD patients (Praamstra and Plat, 2001
; Fielding et al., 2005
). These findings contrast with the view of van Steenbergen et al. (2009
) who claimed that DA bursts were responsible for the reduced conflict adaptation observed in the context of reward.
A further problematic point for the idea that conflict adaptation is triggered by the aversiveness of the efforts involved in cognitive conflict processing is the lack of evidence for the purported negative emotional valence of cognitive conflicts. As shown by Schacht et al. (2010
) in a direct comparison of Go/Nogo and Simon tasks, the emotions elicited by conflicts are task specific and not necessarily aversive. Emotional responses, indicated in a number of psychophysiological parameters, were only present in Go/Nogo conflicts but not in incompatible Simon task trials. Moreover, the construal of conflicts as aversive, adaptation-driving events was further called into question by indications that the emotions elicited in Nogo conflicts seem to be appetitive rather than aversive (cf. Schacht et al., 2009
In sum, the theoretical predictions for the relationship between affect and conflict processing are controversial. Whereas van Steenbergen et al. (2009
) hold that conflict adaptation is triggered by the aversive nature of conflict processing, other findings indicate that conflict adaptation should be facilitated by emotionally positive, DA-releasing events or states.
Here we tested in two experiments with the Simon task whether reward counteracts the presumably negative experience of a conflict and hence reduces conflict adaptation as predicted by van Steenbergen et al. (2009
). In Experiment 1, reward was presented non-contingent to behavior, attempting to replicate the study of van Steenbergen et al. (2009
) with a different conflict task. Because the predicted effect was absent, Experiment 2 explored the effects of presenting reward and punishment contingent upon performance.