Emotion fingerprints or emotion populations? A meta-analytic investigation of autonomic features of emotion categories

Abstract

The classical view of emotion hypothesizes that certain emotion categories have a specific autonomic nervous system (ANS) "fingerprint" that is distinct from other categories. Substantial ANS variation within a category is presumed to be epiphenomenal. The theory of constructed emotion hypothesizes that an emotion category is a population of context-specific, highly variable instances that need not share an ANS fingerprint. Instead, ANS variation within a category is a meaningful part of the nature of emotion. We present a meta-analysis of 202 studies measuring ANS reactivity during lab-based inductions of emotion in nonclinical samples of adults, using a random effects, multilevel meta-analysis and multivariate pattern classification analysis to test our hypotheses. We found increases in mean effect size for 59.4% of ANS variables across emotion categories, but the pattern of effect sizes did not clearly distinguish 1 emotion category from another. We also observed significant variation within emotion categories; heterogeneity accounted for a moderate to substantial percentage (i.e., I2 ≥ 30%) of variability in 54% of these effect sizes. Experimental moderators epiphenomenal to emotion, such as induction type (e.g., films vs. imagery), did not explain a large portion of the variability. Correction for publication bias reduced estimated effect sizes even further, increasing heterogeneity of effect sizes for certain emotion categories. These findings, when considered in the broader empirical literature, are more consistent with population thinking and other principles from evolutionary biology found within the theory of constructed emotion, and offer insights for developing new hypotheses to understand the nature of emotion. (PsycINFO Database Record

Conflict of interest statement

No authors have any financial interests to disclose.

(c) 2018 APA, all rights reserved).

Figures

Figure 1

Flowchart describing identification and screening of articles and studies

Figure 2

Number of effect sizes for each autonomic nervous system measure by emotion category

Figure 3

Number of effect sizes for each emotion category as a function of publication date

Figure 4

Number of effect sizes for each autonomic nervous system measure as a function of publication date.

Figures 5

a–f. Funnel plots of individual effect sizes in our meta-analytic database separated by emotion category. In these plots, precision (1/standard error) is on the y-axis and estimated effect size on the x-axis. Because studies with smaller sample sizes will usually show more variability in effect size, the scatterplot should be the widest at the bottom (i.e., where sample size is smallest) and should progressively narrow as it moves up the y-axis (i.e., as the sample size increases) creating a funnel-like shape. Deviations from this expected form suggests either a) the presence of moderators or b) some publication bias in our sample of studies. Funnel plots for all six emotion categories contained some amount of bias and required imputation (filled black circles denote the imputed missing studies). The diamonds shown below the x-axis illustrate the mean difference (d) before (white diamonds) and after (black diamonds) imputation. Data from the trim and fill analysis are reported in Table 5.

Figure 6

Mean effect sizes plotted for each emotion category with confidence intervals. Larger squares indicate larger numbers of effect sizes in the comparison.

Figure 7

Mean effect sizes and confidence intervals for each of the six emotion categories. Larger shapes indicate greater numbers of effect sizes within the comparison