To fully capture this result pattern (see Nieuwenhuis et al., 2011), a 3-way rANOVA with the additional factor time (early vs. late CNV) was implemented. A main effect of time was present (F(1,21)=75.44, p<0.001), with a higher level of negative-polarity activity in the later window. Again, larger CNV amplitudes were observed for reward cues compared to no-reward cues, resulting in a main effect of reward across both time periods (F(1,21)=22.95, p<0.001). There was also a significant interaction between time and task difficulty (F(1,21)=10.85, p=0.003), due to a larger difference between high-difficulty and low-difficulty trials in the late phase, with high-difficulty trials being more negative. Moreover, a marginally significant three-way interaction between time, task difficulty and reward was observed (F(1,21)=3.52, p=0.075). This 3-way interaction pattern was due to the interaction between task difficulty and reward only arising at a later stage of the preparation process.
