Relationships among locus of control, type of task (visuospatial versus semantic), and arousal or activation by an unexpected preparatory signal.

In this experiment, which is partly a replication of two earlier ones, we tested the hypothesis that the brain self-regulates its own arousal and activation. According to the underlying paradigm, arousal effectuates slower reaction times and depressed EMG activity after an unexpected preparatory signal on a visuospatial choice-reaction task, whereas activation effectuates faster reaction times and elevated EMG activity after an unexpected preparatory signal on a semantic choice-reaction task. The results basically confirm the predictions. The relationship of locus of control scores of the subjects with tonic and phasic EMG activity was also explored. The results clearly and consistently show elevated tonic EMG activity in the left forearm for subjects with an external locus of control. Together the results suggest that the mechanisms involved are partly preconscious and probably related to central catecholaminergic activation systems.