Reynolds, G.D., & Richards, J.E. (2007). Infant heart rate: A developmental psychophysiological perspective. In L.A. Schmidt & S.J. Segalowitz (Eds.), Developmental Psychophysiology (pps 173-210). Cambridge, UK: Cambridge Press.(pdf )
Psychophysiology is the study of the relation between psychological events and biological processes in human subjects. The electrocardiogram (ECG) and heart rate (HR) have been commonly used measures throughout the history of psychophysiological research. Early studies found that stimuli eliciting differing emotional responses in adults also elicited HR responses differing in magnitude and direction of change from baseline (e.g., Darrow, 1929; Graham & Clifton, 1966; Lacey, 1959). Vast improvements in methods of measuring ECG and knowledge regarding the relationship between HR and cognitive activity have occurred. Heart rate has been particularly useful in developmental psychophysiological research. Researchers interested in early cognitive and perceptual development have utilized HR as a window into cognitive activity for infants before they are capable of demonstrating complex behaviors or providing verbal responses. Also, the relation between brain control of HR and the behavior of HR during psychological activity has helped work in developmental cognitive neuroscience. In this chapter, we address the use of the ECG and HR in research on human infants. We review research utilizing three ways in which HR has been used in this work: HR changes, attention phases defined by HR, and HR variability (particularly respiratory sinus arrhythmia). Topics we will focus on are: the areas of the brain that are indexed with these measures, developmental changes associated with these measures, and the relationship of these measures to psychological processes. Before covering research with infants, we will briefly review background information on the heart, the ECG and HR, and its relation to psychophysiology.