Behavioural Friction Theory: Toward a Common Currency for Behavioural Science
Pødenphant Lund, T. (2026a) · Preprint · v15 live on Zenodo (21 August 2026)
Behavioural science has more than 20 research traditions (polyvagal theory, cognitive load theory, self-efficacy, psychological safety, nudge theory, attachment, expectancy-value, and others) that do not talk to each other. This paper places them in one map, with Porges, Bandura, Sweller, Kahneman, Edmondson, and the rest in their specific cell of a four-field by five-layer matrix, and shows what falls out when you do.
| DOI | 10.5281/zenodo.19462499 (concept DOI; v15 is the latest live version) |
| Target venue | Frontiers in Psychology — Hypothesis & Theory (committed; APC waiver application planned) |
| Status | v15 live on Zenodo, published 21 August 2026 |
| Length | ~45k words |
| Author | Tomas Pødenphant Lund [ORCID] |
TL;DR
Behavioural science has produced robust findings across dozens of research traditions, but lacks the integrative architecture needed to connect them. Each tradition operates with its own vocabulary, level of analysis, and scope conditions, leaving researchers without a principled basis for relating constructs across domains.
This paper introduces Behavioural Friction Theory (BFT) and proposes friction (the cost a regulatory system assigns to a potential action in a given situation) as a candidate common currency for behavioural science. The proposal is programmatic: friction functions as a scientific currency rather than a unifying metaphor to the degree it is independently operationalised at the field level, and no validated instrument yet measures field-level friction. BFT organizes the regulatory system across four computational fields (Safety, Meaning, Ability, Effort) and four functional layers (Biological, Emotional, Inner, Cognitive) plus an external level, and describes a single central mechanism (the RACE model) through which regulatory outcomes are determined by the interaction of pressure and bandwidth. BFT adds no new mechanism: its components are inherited and cited at the point of use, and where BFT coincides with one of them, that formalism has priority.
Friction as a candidate common currency offers a principled account of three longstanding theoretical problems:
- Integration: a field-by-layer map on which polyvagal theory, self-efficacy research, cognitive load theory, psychological safety research, and nudge theory can be located as candidate descriptions of specific regions of one proposed regulatory landscape.
- Motivation: the hypothesis that motivation loses incremental predictive power once field-level friction is independently measured by validated instruments (P18), offered as a testable reduction rather than a categorical dismissal.
- Nature and nurture: the distinction reframed as a question about intervention, where matched friction profiles are predicted to respond equivalently whether those profiles have constitutional or experiential origins (P20).
Thirty formal propositions are derived from the theory, each with existing empirical support and a minimal test design, and framed as a programme to be pre-registered. Two of them state headline reframes and stand as hypotheses within that programme rather than as established claims. BFT is presented as a theoretical framework inviting empirical scrutiny. It does not replace existing theories; it provides the architecture within which they can be compared, connected, and extended.
Key concepts
- Four functional fields: Safety, Meaning, Ability, Effort — the dimensions through which the nervous system assigns regulatory cost (the fifth-field challenge stands: candidate fifth fields — urgency, social pressure, identity, uncertainty, fairness — each decompose into the four)
- The fields have distinct computational forms: Safety is an approach–avoid valence readout (safe = the absence of an unsafety signal, graded rather than a binary switch); Meaning is a selection among competing directions; Ability is a match of capacity to task-demand (where the skill–challenge inverted-U lives); Effort is an aggregate, second-order cost over the other three. Fairness enters as the social case of mirror-friction, read through the four rather than as a field of its own
- Four functional layers plus an external level: Biological, Emotional, Inner, Cognitive, and the external environment that loads them — nested timescales of friction-modulation
- The RACE model: parallel evaluation of competing routes, accumulation under bandwidth, irreversible commitment
- The Net Friction Rule: a system acts when the expected reduction in overall friction over time exceeds the present cost — and when the friction associated with acting does not exceed substrate capacity
- Pressure, threshold, reactance: the dynamics of route-competition under load
Companion papers
Paper 1 (Lund 2026b) is the instrument paper: competing-routes measurement on transformer logprob distributions, quantifying token by token how sharply a model's candidate continuations compete. The relation to it is a proposed nesting, BFT ⊂ FT, where FT names the general route-competition frame of which the biological case is one instance. This paper owns the content of the four fields, their computational forms, and their native always-on organisation in the biological substrate. Whether friction and the four-field structure generalise beyond biology is carried in that companion as an open research direction, framed as a resource-rational task analysis rather than a settled law, and it is not load-bearing for the behavioural and clinical propositions developed here. See Paper 1 →