Phenotypic correlations capture between-individual correlations underlying behavioral syndromes

Abstract

The presence of variation in behavior on the between-individual level is considered the hallmark of personality. In contrast, behavioral syndromes are commonly recognized when documented on the phenotypic level, which is a mix of between-individual and residual (within-individual) correlations. Phenotypic and between-individual correlations need not align, and investigations on different levels of the same syndrome may hence lead to opposite inferences. Between-individual correlations, arguably, provide stronger evidence for an intrinsically determined behavioral syndrome than phenotypic correlations. We compiled 109 literature estimates of between-individual and phenotypic correlations between behaviors from 30 studies, performed on 22 species covering a wide range of taxa. Contrary to our expectation, the phenotypic correlation in behaviors was, on average, a reasonable predictor of the between-individual correlation in terms of magnitude and sign. Although our finding does not warrant the use of the phenotypic correlation as a suitable approximation of the between-individual correlation for any particular study, it does suggest that the phenotypic correlations used to infer the majority of behavioral syndromes to date have provided a reasonable characterization of syndrome associative strength. Aspects of personality often correlate and are then said to form a behavioral syndrome. Syndromes are interesting because they signal that multiple behaviors may share causal drivers. Most syndromes to date are based on correlations of measured behaviors (phenotypes), but any pattern on the phenotypic level is likely influenced by uncontrolled associations between the focal behaviors which are expected to reduce the phenotypic correlation relative to the correlation on the underlying individual level. If so, behavioral ecologists may have underestimated the associative strength of behavioral syndromes. Based on over 100 published estimates of individual-level and phenotypic correlations between aspects of personality, we show that the phenotypic correlation provides a reasonable estimate of the magnitude and sign of individual-level correlations.