To perform the GENERATE+MONITOR condition optimally, therefore, participants had both to (a) make voluntary decisions about which action to select and (b) monitor the outcome of their choices to work out which set of response rules is in place and to modify their behaviour accordingly. By contrast, in the GENERATE or FIXED+MONITOR versions, participants only had to contend with one of these factors when switching between response sets. By contrasting in each condition the signal time-locked to the switch cue with that at the stay cue, it was possible to assess the degree to which activity in dorsal ACC is driven by voluntary response selection, performance monitoring or a combination of the two factors.
