Invariants of developmental variation

Science is concerned in part with the discovery of invariants such as the conservation of mass and energy or the sum of the internal angles of a triangle. However, in psychology the discovery of true invariants is obstructed by adaptive responses to the environment, developmental change, and the striking range of phenotypic variation that must be explained, from common variation in cognitive and motor skills to developmental delay, psychopathology, and expertise. Capturing this breadth of phenomena necessarily demands a level of abstraction that seeks qualitative invariants in the stable architectural features and adaptive processes that reveal the wide spectrum of individual differences. The aim of this paper is to identify candidate qualitative invariants of this sort. Building on the bounded rationality paradigm, I present a new formalisation illustrating how adaptive search and satisficing shape diverse developmental outcomes over and above the fundamental neurogenetic variation that drives this behaviour, thereby detailing a reciprocal feedback loop that is often overlooked despite its importance in interactionist frameworks like probabilistic epigenesis. From this formalisation, I then distil a series of candidate qualitative invariants of developmental variation, describing their theoretical and applied significance and empirical support. This includes (i) resource-complexity asymmetry, (ii) value-guided search and satisficing, (iii) dynamic aspiration, (iv) problem space construal, (v) local model updating, (vi) action-outcome stochasticity, and (vii) structured problem ecology. These qualitative invariants should be incorporated into any complete process theory of the behavioural mechanisms underlying individual differences in human development.