Developmental perspectives on personality: implications for ecological and evolutionary studies of individual differences

Abstract

Developmental processes can have major impacts on the correlations in behaviour across contexts (contextual generality) and across time (temporal consistency) that are the hallmarks of animal personality. Personality can and does change: at any given age or life stage it is contingent upon a wide range of experiential factors that occurred earlier in life, from prior to conception through adulthood. We show how developmental reaction norms that describe the effects of prior experience on a given behaviour can be used to determine whether the effects of a given experience at a given age will affect contextual generality at a later age, and to illustrate how variation within individuals in developmental plasticity leads to variation in contextual generality across individuals as a function of experience. We also show why niche-picking and niche-construction, behavioural processes which allow individuals to affect their own developmental environment, can affect the contextual generality and the temporal consistency of personality. We conclude by discussing how an appreciation of developmental processes can alert behavioural ecologists studying animal personality to critical, untested assumptions that underlie their own research programmes, and outline situations in which a developmental perspective can improve studies of the functional significance and evolution of animal personality.

Are personality differences in a small iteroparous mammal maintained by a life-history trade-off?

“…Variation in individual male plasticity with age was high in all age classes, however, suggesting a cautious interpretation of the individual  age interaction. Since we know so little about the ontogeny of personality traits in mouse lemurs and other species, only future studies can reveal patterns and mechanisms of individual personality development [27,38].…”

“…I defined three age classes: yearlings (class 1, 1 yr; n males ¼ 25, n females ¼ 18), individuals of average age (class 2, .1 yr and ,3 yr; n males ¼ 42, n females ¼ 29) and individuals older than the average life expectancy (class 3, !3 yr; n males ¼ 9, n females ¼ 10). Individual identity (ID) and the total number of trials performed were added as correlated random effects in each model, forming a random slope model [27]. This model structure included between-individual variation in slope of the within-individual relationship between composite behavioural variables and the number of trials performed, as well as between-individual variation in intercepts.…”

Animal personality and state–behaviour feedbacks: a review and guide for empiricists

“…Individual divergence due to positive feedback would typically cease at some point in time either because of biological floors or ceilings to both state and behaviour, because behaviour is open for modification only during certain developmental stages [9] or because the effect of state on behaviour (or vice versa) is non-linear. At such 'end stages', within-individual correlations would decrease to zero and be replaced by stable 'among-individual correlations' [60].…”

“…Empirical studies show that animal personalities and behavioural syndromes (correlations across contexts) vary as a function of ecology [4,5]; for example, aggressiveness and boldness are often positively correlated but the strength of this correlation varies depending on the predation regime [6,7]. Variation in syndrome structure also exists across different temporal scales; for instance, early experiences (e.g., exposure to stressors) can have large effects on the development of personality structure but such effects can either be temporary or permanent [8][9][10]. Understanding the processes explaining the emergence of personality differences and variability of syndrome structure within and among species represents a major current topic in adaptive personality research.…”

Behavioral idiosyncrasy reveals genetic control of phenotypic variability

“…Although studies of morphology (5-7) and animal breeding (8,9) have long noted the heterogeneity of variance among genotypes, this axis of variation has received little attention compared with the effect of genetic variation on trait means. As a result, the mechanisms by which variable phenotypes arise from a uniform genetic background are still poorly understood, particularly in the context of behavior, where variability may be a critical determinant of phenotypic differences (10,11). Most recently, with the advent of genome-wide association studies, several groups (3,4,12,13) have mapped quantitative trait loci affecting variance (vQTLs) by comparing phenotypic variances among individuals that share alleles.…”