Midfrontal theta as an index of conflict strength in approach-approach vs. Avoidance-avoidance conflicts.

The seminal theory of motivational conflicts distinguishes between Approach-Approach conflicts, in which a decision is made between desirable alternatives, and Avoidance-Avoidance conflicts, in which a decision is made between undesirable alternatives. The behavioral differences between Approach-Approach and Avoidance-Avoidance conflicts are well documented: both Lewin's and Miller's original conceptualization, as well as abundant empirical research that followed, showed that Avoidance-Avoidance conflicts are more difficult to resolve than Approach-Approach ones. However, there is little to no research looking into the neural underpinnings of the differences between the two conflict types. Here, we show that midfrontal theta, an established neural marker of conflict, distinguished between the two conflict types such that midfrontal theta power was higher in Avoidance-Avoidance conflicts than in Approach-Approach conflicts. We further demonstrate that higher midfrontal theta power was associated with shorter decision times on a single trial basis, indicating that midfrontal theta played a role in promoting successful controlled behavior. Taken together, our results show that Approach-Approach and Avoidance-Avoidance conflicts are distinguishable on the neural level. The implications of these results go beyond motivational conflicts, as they establish midfrontal theta as a measure of continuous degree of conflict in subjective decisions.