A longitudinal study of cardiac component analysis

The purpose of this study was to examine the reliability of a physiological event over several weeks. The physiology analyzed was the electrical event of the heart. Two operationally defined components of the typical heart response were examined. The technique gave very reliable data within a given day. Moreover, when the data for 20 weeks were added, the overall standard deviation was very small, but there were unpredictable physiological variations from day to day. The data suggest that comparisons between psychological tasks using physiological events as the dependent measure are best done in close temporal contiguity.