and then accelerates rapidly. What was the baby's emotional response? We would have to observe whether he laughed or cried. We do know from the HR record and its correlates in other situations that he oriented at first and then became aroused, but we know nothing about the content of his response nor why he responded as he did. To study new emotional situations and behavioral responses, HR changes will not stand alone. Behavioral observations remain the anchor for a psychological interpretation.
Individual differences in HR responses are another problem. Stable patterns of individual responses are not well established, as Campos notes, although the test-retest correlations are above zero. Because behavioral, emotional responses are not perfectly measured either ( Scarr & Salapatek, 1970), there are compound problems with an unstable index of unstable criterion measures. This criticism is not directed toward HR alone; most experimental measures are not highly reliable. For the purposes of seeking age-related changes in HR responses, a moderately reliable measure will probably do. It would be more difficult, however, to explore individual differences in HR changes longitudinally.
None of the criticisms above points in any sense to a fatal flaw. They are intended as warnings about the problems of reductionist measures that lack perfect correlations with the behavioral criteria, that are not perfectly reliable, and that do not convey all of the necessary information about emotional development. Campos never made any such claims. Instead, he demonstrated in fascinating ways that HR can be a useful measure to accompany behavioral observations. Not all claims for psychophysiology are so circumspect.
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Scarr, S., & Salapatek, P. Patterns of fear development during infancy. Merrill-Palmer Quarterly, 1970, 16, 53-90.
Sroufe, L. A., Waters, E., & Matas, L. "Contextual determinants of infant affective response". In M. Lewis & L. Rosenblum (Eds.), Origins of fear. New York: Wiley, 1974. Pp. 49-72.
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