Within the Agency–Process–Scale (APS) framework, behaviour refers to the observable expression of biological agency through interactions with internal and external conditions. Behaviour includes the actions, responses, adjustments, and regulatory activities by which living systems engage with circumstances affecting viability, functioning, and adaptive persistence.
Behaviour is not restricted to animals or organisms possessing nervous systems. Plants alter growth patterns in response to light, water, and nutrients. Microorganisms move toward favourable conditions and away from harmful ones. Cells regulate internal processes in response to changing environmental conditions. In each case, behaviour reflects the active engagement of living systems with conditions that matter for organised persistence.
Within APS, behaviour is closely related to agency and cognition but is not identical to either. Biological agency refers to the capacity of living systems to initiate, regulate, and coordinate viability-oriented interactions. Cognition refers to the processes through which organisms acquire, integrate, and utilise information about internal and external conditions. Behaviour is the observable expression of these underlying capacities. In simplified form, agency enables action, cognition informs action, and behaviour is the enacted outcome.
Behaviour is guided by biological meaning, evaluation, and value. Living systems encounter conditions that possess significance for viability and functioning. Through evaluation, organisms assess that significance, and repeated patterns of evaluation stabilise into biological values. Behaviour expresses the ways organisms act in relation to these meaningful and valued conditions.
APS treats behaviour as fundamentally context-sensitive. The same organism may behave differently under different environmental, physiological, developmental, or social circumstances. Behaviour is therefore not simply a fixed output generated by internal mechanisms. It emerges through ongoing interactions between living systems and the conditions in which they are embedded.
Behaviour operates across biological scales. Molecular regulation, cellular responses, physiological adjustments, organismal activities, social interactions, and ecological processes may all exhibit behavioural characteristics when they involve context-sensitive responses to conditions affecting organised persistence. APS therefore treats behaviour as a multiscale expression of agency rather than as a phenomenon restricted to whole organisms.
Within APS, behaviour is understood as one of the principal ways biological agency becomes visible. It reveals how living systems regulate interactions with their environments, respond to changing conditions, and contribute to the maintenance of viability, functioning, and adaptive persistence across the living world.