Changes in alertness and processing capacity in a serial learning task

Second-to-second changes in processing capacity were examined using a concurrent task paradigm involving serial learning and simple reaction time (RT) in two experiments. Experiment 1 demonstrated the feasibility of combining probe RT with a slow-paced serial learning task including perceptually isolated items. Experiment 2 employed the same concurrent tasks to compare cardiac interbeat interval (IBI, the reciprocal of heart rate) with probe RT. Second-to-second changes during item processing were found consistently for both measures. However, these changes appeared to be more related to observing and response requirements than to the specific cognitive processes required by the tasks. Correctly anticipated items were associated with (l)RT changes, suggesting heightened allocation of capacity, and (2)a cardiac IBI response of episodic cardiac deceleration imposed upon the task-induced cardiac speeding. The probe RT and cardiac IBI measures showed reasonable convergence in assessing the allocation of processing capacity. The concept of the accessibility of allocated capacity was introduced in considering instances of the divergence of probe RT and cardiac IBI.