The error-related negativity (ERN) is a component of the event-related brain potential (ERP) that is associated with action monitoring and error detection. The ERN amplitude reflects attentional resource allocated to error detection. The present study examined whether discrete or gradational allocation strategy of attentional resource in error detection using the ERN amplitude. Only Eriksen flanker task was used in the single task condition. Eriksen flanker task was used as a primary task and Sternberg memory search task was used as a secondary task in the dual task conditions. The task difficulty of the secondary task manipulated in the present study included the memory load. Memory set sizes of 2, 4 and 6 were used in the Sternberg memory search task (M2, M4 and M6 conditions). The results indicated that reaction time was gradually delayed in the primary task as the task difficulty of the secondary task gradually increased. However the ERN amplitude of the primary task decreased in M6 condition alone. In conclusion, discrete allocation strategy of attentional resource was adopted in the error detection.
