Stability and instability of childhood traits: implications for personality development of animals.

Concepts of animal personality and human temperament are nearly identical, both emphasizing overt behaviors rather than conscious processes, and assuming a primary role of biology in shaping individual differences. A point of divergence is emphasis on development among temperament scholars. Whereas most definitions of personality and temperament emphasize differential continuity-the maintenance of individual differences in behavioral tendencies over time-several behaviors demonstrate absolute discontinuity-age-related changes in mean levels. Attention to species-wide changes in behaviors may generate insight regarding the forces that govern individual differences. Differential continuity may also be heterotypic, with an inferred genotypic attribute being manifest in different behaviors at different ages. Structural continuity-persistence of correlational patterns among variables at different ages-represents a tool for identifying coherence in the common underpinnings of these diverse behaviors. This article describes research exemplifying these forms of continuity in humans, and suggests potential implications for animal personality investigations.