Behavioural Friction Theory: Toward a Common Currency for Behavioural Science

Behavioural science has produced robust findings across dozens of research traditions, yet lacks the integrative architecture needed to connect them — a common unit or map for relating constructs across domains and anticipating cross-field interactions. Behavioural Friction Theory (BFT) proposes friction — the cost a regulatory system assigns to a potential action in a given situation — as a candidate common currency for behavioural science, a programmatic proposal whose status is contingent on independent field-level operationalisation. It offers a candidate decomposition of that cost into four fields (Safety, Meaning, Ability, Effort) across five layers (Biological, Emotional, Inner, Cognitive, External), with resolution modelled as a pressure-dependent race. BFT adds no new mechanism: its components are inherited and cited at the point of use (accumulation-to-threshold, expected value of control, hierarchical control, ordered appraisal). The contribution is threefold: (1) a field × layer map on which traditions such as polyvagal theory, self-efficacy research, cognitive load theory, psychological safety, and nudge theory are located as candidate descriptions of regions of a proposed shared landscape; (2) design heuristics motivated by the decomposition (baseline pressure as an intervention precondition, weakest-field prioritisation, and a bounded-compensation prediction); and (3) thirty formal, individually-testable propositions, each with a minimal test design, framed as a pre-registerable programme for testing whether the four fields are functionally dissociable. The central requirement is stated plainly: field-level friction has no validated measurement instrument yet, so several propositions are not presently runnable — they are tests to be run, not results in hand. The decomposition is falsified if the four fields do not dissociate under manipulation, or if a unitary-cost model — expected value of control, active inference, or a resource-rational model that collapses to a single cost — accounts for the same variance. BFT is offered as an architecture within which existing theories can be compared, connected, and extended, not as a replacement for them. v15 (August 2026) — positioning update. The framework is situated relative to Resource-Rational Analysis (Lieder & Griffiths, 2020), and the common currency is stated as a candidate, programmatic account rather than a substrate-universal law; the architecture and propositions are unchanged in substance. Earlier versions remain accessible through the version history.