The role of plasticity, trade-offs, and feedbacks in shaping behavioral correlations

Abstract

How behaviors vary among individuals and covary with other behaviors has been a major topic of interest over the last two decades, particularly in research on animal personality, behavioral syndromes, and trade-offs with life-history traits. Unfortunately, proposed theoretical and conceptual frameworks explaining the seemingly ubiquitous observation of behavioral (co)variation have rarely successfully generalized. For example, the "pace-of-life syndrome hypothesis"proposes that behaviors, life-history, and physiological traits should be correlated in a predictable manner. However, these predictions are not consistently upheld. Two observations perhaps explain this failure: First, phenotypic correlations between behaviors are more strongly influenced by correlated and reversible plastic changes in behavior than by among-individual correlations which stem from the joint effects of genetics and developmental plasticity. Second, while trait correlations are frequently assumed to arise via trade-offs, the observed pattern of correlations is not consistent with simple pair-wise trade-offs. A possible resolution to the apparent inconsistency between observed correlations and a role for trade-offs is provided by state-behavior feedbacks. This is critical because the inconsistency between data and theory represents a major failure in our understanding of behavioral evolution. These two primary observations emphasize the importance of an increased research focus on correlated reversible plasticity in behavior - frequently estimated and then disregarded as within-individual covariances.