When you think you can go no further, you are only halfway to where you can truly go: Manipulating speed-accuracy trade-off in task instructions affect ERP amplitudes in a visual cued Go/NoGo task
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- Institutt for psykologi 
Assessments of attentional processes through traditional neuropsychological tests or electrophysiological methods seldom control for the possible effects of nuances in the instructions given. The present study documents significant effects of experimentally manipulating the weighting of speed and accuracy when giving instructions in a cued Go/NoGo task on behavioral parameters and amplitudes of several event related potentials (ERPs) recorded from a student population (n = 35). The order of the speed and accuracy conditions was randomized using a crossover design. The results demonstrate significant effects on the amplitudes of the P3NoGo and contingent negative variation (CNV) waves, and three corresponding independent components (ICs) decomposed by independent component analysis (ICA). The amplitudes of all five potentials studied increased significantly when focusing on speed compared to accuracy. The latencies of the P3NoGo wave and ICs remained unchanged. These results underline the importance of controlling for the effect of instructions when conducting research on ERPs or when considering application of this method in the clinic. The P3NoGo and CNV ERPs have previously been linked to processes of attentional control from the modified supervisory attentional system (SAS) model. In light of this model, the speed condition can be interpreted as increasing recruitment of the attentional control processes of energization and monitoring.