Revisiting the lack of association between affect and physiology: Contrasting between-person and within-person analyses.

Health Psychology 2017, Vol. 36, No. 8, 811– 818 © 2017 American Psychological Association 0278-6133/17/$12.00 http://dx.doi.org/10.1037/hea0000466 This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Revisiting the Lack of Association Between Affect and Physiology: Contrasting Between-Person and Within-Person Analyses Matthew J. Zawadzki Joshua M. Smyth and Martin J. Sliwinski University of California–Merced Pennsylvania State University John M. Ruiz William Gerin University of Arizona Pennsylvania State University Objective: Despite experimental manipulations that reliably elicit affective and physiological responses, the relationship between the two frequently appears small or nonexistent. We propose that this is, at least in part, due to a mismatch between the nature of the question being asked and the analytic methods applied. For example, to test if levels of affect reliably covary with physiology over time—a within- person question— one cannot apply analytic approaches that test whether people are similarly reactive across domains—a between-person question. The purpose of this paper is to compare within-person and between-person analyses testing the association between affect and physiology. Method: Participants (N ⫽ 60) recalled an event from their lives that made them angry. Self-reported anger and objective blood pressure levels were recorded at baseline, after the recall, and 5 times during recovery. Results: Between-person correlations between anger and blood pressure were nonsignificant across all phases of the study, suggesting that those least/most reactive for anger were not least/most reactive for blood pressure. These null findings held regardless of whether linear or nonlinear assumptions were modeled. In contrast, within-person multilevel modeling indicated a clear relationship, suggesting that when a person was angrier that person’s blood pressure was higher compared with when that person was less angry. Conclusion: Results suggest the importance of appropriately matching analytic strategy to the nature of the question regarding the relationships between affect and physiology. Implications for past and future research are discussed. Keywords: affect, correlation, physiology, anger, blood pressure pressure [BP]), the relationship between the changes in affect and physiology is often statistically nonsignificant or modest in mag- nitude. For example, a meta-analysis indicated that changes in negative affect due to a stressor only accounted for 2–12% of changes in cardiovascular responses despite large changes in car- diovascular responses after the stressor (Feldman et al., 1999). If participants report more negative affect as a result of a stressor, and their bodies react to the same stressor, then one would rea- sonably expect that the changes in affect and physiology would be strongly associated. Measuring affect and physiology and examining how these variables relate and change over time are important questions for biobehavioral and psychophysiological research. Such evidence helps to better understand the etiology and progression of disease and inform interventions. However, researchers studying the asso- ciation between affective and physiological changes in the labo- ratory face a conundrum. Although experimental manipulations often increase self-reported negative affect (e.g., the experience of anger) and influence physiological responses (e.g., raise blood Understanding the Lack of Correspondence This article was published Online First March 9, 2017. Matthew J. Zawadzki, Department of Psychological Sciences, Univer- sity of California–Merced; Joshua M. Smyth, Department of Biobehavioral Health, Pennsylvania State University; Martin J. Sliwinski, Department of Human Development and Family Studies, Pennsylvania State University; John M. Ruiz, Department of Psychology, University of Arizona; William Gerin, Department of Biobehavioral Health, Pennsylvania State University. Portions of this work were presented in an oral session at the 2013 Annual Meeting of the American Psychosomatic Society in Miami, Flor- ida. Correspondence concerning this article should be addressed to Matthew J. Zawadzki, Department of Psychological Sciences, University of California–Merced, 5200 North Lake Road, Merced, CA 95343. E-mail: mjz172@psu.edu Many explanations have been offered for the lack of association between affect and physiology (Gerin et al., 1999; Hilmert & Kvasnicka, 2010). For example, how variables are measured may not be adequate because affect is usually measured at the end of a study period (e.g., baseline) whereas physiology is often continu- ously measured (Feldman et al., 1999; Lovallo & Gerin, 2003). Another explanation questions the ability of participants to accu- rately report on their affective states (Sato & Kawahara, 2011; Thomas & Diener, 1990) and if self-reports of affect are valid indicators of one’s “true experience” (Russell & Barrett, 1999). For example, individuals may report how they want others to think they are feeling rather than what they are actually experiencing