As has been observed in previous studies, the signal in the dorsal ACC increased when switching between response rules whenever participants were either able to exercise their own volition when choosing a response or had to attend to the feedback to work out which response set to use (in all conditions except CONTROL). Importantly, when the two conditions in which subjects were uncertain about which rule set was in place after a switch were compared, activity levels were significantly greater in the ACC when participants had to decide what response to make and had increased degrees of freedom of choice (GENERATE+MONITOR) compared to when they were told what to do (FIXED+MONITOR) (Figure 3a, b). This implies that an opportunity to choose voluntarily what action to make is an important component of ACC function. However, it is not merely the act of deciding what to do that is driving the ACC response here; the signal change in the identical region of dorsal ACC most active in the previous monitoring comparison (Figure 3a) was also significantly more active when participants had to
