Figure 1.
Schematic drawing of the modified Simon task. Each trial started with the presentation of a congruency cue. In the choice condition, participants indicated their preference for receiving a congruent or incongruent target stimulus by selecting either C (congruent) or I (incongruent) with the middle finger or the index finger of the left hand. In the no-choice condition (data not shown here), the congruency cue either conveyed C or I information. The target matched the cue in 70% of the trials (valid trials; top), whereas in 30% of the trials, target congruence did not match the cue (invalid trials; bottom). The target stimuli consisted of green and red circles that were associated with a left and right button press, respectively, with the index or middle fingers of the right hand. In congruent trials, responses were spatially compatible with the location of the target stimulus (e.g., left green circle leads to an index finger response), whereas in incongruent targets, participants' responses were spatially incompatible with the location of the stimulus (e.g., left red circle leads to a middle finger response).