A reference for how Behavioural Engines works: its models, workflow, features, and limits.
Behavioural Engines runs the standard models of behavioural economics, including Prospect Theory, Hyperbolic Discounting, and Rational Inattention, in the browser. You set the parameters, run a deterministic simulation, compare results, and export the output. You can also collect real responses through shareable surveys and fit model parameters to them.
Every model is implemented from a peer-reviewed paper, with the full citation, the equations, and an explanation of each parameter.
The standard models of behavioural science live in papers and textbooks. To run one you normally have to write code yourself or work within whatever a statistics package supports. Behavioural Engines puts working implementations of these models in one place in the browser.
Each model is implemented from its source paper with the original mathematics, given parameter controls with sensible ranges, and connected to charts so you can see what changes when you change an input.
Select a model
Choose a model in the workspace. You can switch between models with the top-bar tabs or the ⌘K command palette.
Configure parameters
Adjust the core and advanced coefficients, load a saved preset, or start from one of the pre-built scenarios.
Run the simulation
Press Run Simulation (or ⌘↵). The backend computes the result deterministically and returns the metrics and chart data.
Compare & explore
Pin a result as a baseline, change parameters, and run again. Both results appear side by side in the analysis panel and as overlaid lines on every chart.
Review & export
Every run is saved to your history with a searchable name. Pro users can re-run past simulations, copy shareable links, and export results as PDF, CSV, or JSON.
Run an experiment
Click Run Experiment on a supported model and share the generated link. Fitted parameters appear on the Experiments page as responses arrive.
Structural Adoption
Applied Microeconomics
Logistic structural model estimating bounded adoption probability from behavioural levers with diminishing incentive returns.
Prospect Theory
Behavioural Economics
Non-linear value model with probability weighting and loss aversion.
Hyperbolic Discounting
Behavioural Economics
Comparative intertemporal choice model contrasting hyperbolic and exponential time discounting.
Expected Utility Theory
Classical Economics
Normative decision model computing expected utility under constant relative risk aversion (CRRA).
Inequity Aversion (Fehr–Schmidt)
Behavioural Economics
Structural social-preference model where utility depends on one's own payoff and on payoff differences relative to others.
Rational Inattention
Behavioural Economics
Decision model where agents optimally limit attention due to costly information processing.
Regret Theory
Behavioural Economics
Counterfactual utility model where outcomes are evaluated against what the foregone alternative would have given in the same state.
Workspace
Parameter control
Every coefficient in every model is adjustable. Core inputs are always visible, and advanced options sit behind a collapsible panel.
Parameter presets
Save named configurations per model. Presets sync across devices for signed-in users via server-side storage.
Scenario library
Each model comes with pre-built scenarios based on real-world situations, which give you a working configuration to start from.
Command palette
Press ⌘K (or Ctrl+K) to open a searchable command palette. Navigate to any model or page without touching the mouse.
Simulation & Analysis
Comparison mode
Pin any result as a baseline, then adjust parameters and re-run. Metric panels show both side-by-side; charts overlay dashed baseline lines against solid current lines.
Visual charts
Every model renders its curves as interactive charts: value functions, discount curves, probability weighting, and the rest.
Live analysis
Results appear in a structured analysis panel with clearly labelled metrics, colour-coded by sign, immediately after each run.
History
Simulation logs
Every run is stored with its full parameters, results, model version, and timestamp. Paginated and searchable.
Named runs
Give any simulation run a custom name directly from the History page or the detail view. Names sync across devices.
Re-run
Load any past simulation's parameters back into the workspace with one click and re-run with modifications.
Experiments
Shareable surveys
From any supported model, click Run Experiment to generate a shareable link. Respondents answer a short series of either/or choice questions without creating an account, and each receives a personalised reading of their results.
Fitted parameters
Each response is converted into fitted model parameters by revealed-preference estimation. The experiment page shows per-parameter distributions with mean, standard deviation, median, and range.
Pause & resume collection
Pause an experiment to stop accepting responses, and resume it at any time. While paused, the survey link shows a closed notice. Plus accounts can hold 3 experiments; Pro and Lifetime have no limit.
CSV export
Download every respondent's fitted parameters, submission date, and duplicate-network flag as CSV for analysis in Excel, Python, R, or SPSS.
Exports & Sharing
Export as PDF
Generate a formatted PDF of a simulation, including its parameters, results, and metadata.
Export as CSV
Download structured tabular output for further analysis in Excel, Python, R, or any data tool.
Export as JSON
Download the full simulation object as JSON for use in your own pipelines.
Shareable links
Copy a direct link to any saved simulation run and share it with colleagues. The link preserves parameters and results.
Experiments measure behavioural parameters from real choices. Respondents answer a series of binary questions, and the platform estimates the parameter values that best explain their answers by maximum likelihood.
Task battery
Each experiment presents a fixed battery of calibrated either/or choice tasks. For Prospect Theory this is 13 tasks: five mixed gambles against a certain £0 (identifying loss aversion λ), four gain gambles at small and large probabilities (identifying probability weighting γ), and four 50/50 gain gambles against certain amounts (identifying value curvature α). Each task is constructed so its indifference point sits at a known parameter crossover, meaning every answer rules parameter regions in or out.
Estimation
Estimation is two-stage. A coarse grid search (512 candidate (α, λ, γ) triples, ties resolving towards the Kahneman–Tversky empirical medians) finds a robust starting point, then a maximum-likelihood refinement under a logistic choice rule produces continuous estimates. A weak prior centred on the grid winner regularises the fit when a respondent's choices are perfectly consistent, and standard errors are derived from the curvature of the penalised likelihood where it is well conditioned.
Data quality
One response is accepted per device via an idempotent respondent token, and responses sharing a network are flagged (not excluded) in the researcher's results, since shared networks are common in classroom settings. Raw choice data and fitted parameters are exportable as CSV for external analysis.
Limitations
With a short series of binary choices, the data can be consistent with several parameter combinations; standard errors are reported where estimable, and results should be read as behavioural profiles rather than precise psychometric measurements. Estimates are regularised towards population-typical values when responses carry little information. Experiments are currently available for Prospect Theory and Hyperbolic Discounting, with further models planned.
Any experiment can also be answered by AI respondents. Each synthetic respondent is a real anonymised census record narrated as a first-person persona; a language model answers the experiment's choice tasks while conditioned on that persona, and the platform fits parameters from its answers exactly as it does for humans.
Method
This is the silicon sampling method of Argyle, Busby, Fulda, Gubler, Rytting & Wingate (2023), “Out of One, Many: Using Language Models to Simulate Human Samples”, Political Analysis 31(3). Conditioning a language model on socio-demographic backstories makes its answers statistically resemble those of the matching human subgroup. This platform applies the method to behavioural-economics parameters rather than attitudes.
Personas
UK personas are sampled from the ONS 2011 Census Microdata Teaching File (a public 1% sample of England and Wales); US personas from ACS 2023 PUMS microdata covering all states. Because whole records are sampled, age, sex, income, education, occupation, and region keep their real joint distribution. Sampling is seeded, so any audience is exactly reproducible. Each generated audience records the model, prompt version, and seed used.
Constraints
The model's only permitted output is a choice of A or B for each task; anything else is rejected and retried once, then discarded. Option order is randomised per respondent to cancel position bias. Raw model text is never stored or displayed; every number and sentence a researcher sees is computed by the platform from validated choices.
Validation
Synthetic data approximates human responses and should be validated against them. When an experiment holds both cohorts, the results page reports each parameter's human and synthetic means, the variance ratio, and a two-sample Kolmogorov–Smirnov test, alongside the published literature benchmarks. Synthetic respondents are always flagged, in the interface and in every export. Validation audits pin every run to a single model, so measured noise is response noise rather than disagreement between providers.
Monthly allowance
Every paid plan includes 500 synthetic respondents and 10 audience generations per calendar month; a single generation can hold up to 100 respondents. Validation audits draw from the respondent allowance but do not use a generation. Pausing a generation returns its unused respondents to your allowance until you resume. Current usage is shown on your account page and in the generate dialog.
Data sources
Every demographic weight and persona record traces to a published table:
Understanding what this platform is not:
Real behaviour is probabilistic even though these models are deterministic. Incentives act through perception as well as objective value. Friction reduces action even when incentives are positive. Social adoption can amplify small initial differences. Every output reflects the model structure and is not an empirical claim about any population.
Research use should cite the platform with the method versions in effect when the data were collected. Every experiment's replication bundle records its prompt version, estimator specification, parameter bounds, seeds, and per-response provenance, so any reported estimate can be re-fitted independently from the raw choices. Cite as software, and state the prompt version from your bundle:
@software{behavioural_engines,
title = {Behavioural Engines: parameter estimation and
synthetic audiences for behavioural-economics models},
author = {Speed, Joe},
year = {2026},
url = {https://behaviouralengines.com},
note = {Prompt version and estimator specification as recorded
in the experiment's replication bundle}
}Method changes are versioned: the conditioning prompt carries an explicit version stamped on every synthetic response, and estimator changes are documented in the methodology section above. Synthetic cohorts are reproducible from their recorded seed, model, and prompt version, subject to the underlying language model remaining available.
Conditional Logit Analysis of Qualitative Choice Behavior
1974Daniel McFadden · Frontiers in Econometrics
The structural basis for the Adoption model: conditional logit analysis of discrete behavioural choice.
Prospect Theory: An Analysis of Decision under Risk
1979Daniel Kahneman & Amos Tversky · Econometrica
The basis of the Prospect Theory model: value function, loss aversion, and probability weighting.
Golden Eggs and Hyperbolic Discounting
1997David Laibson · Quarterly Journal of Economics
Introduces quasi-hyperbolic discounting and present bias in intertemporal choice.
Theory of Games and Economic Behavior
1944John von Neumann & Oskar Morgenstern · Princeton University Press
The axiomatic foundation of Expected Utility Theory and rational decision-making under uncertainty.
A Theory of Fairness, Competition, and Cooperation
1999Ernst Fehr & Klaus M. Schmidt · Quarterly Journal of Economics
The Fehr-Schmidt inequity aversion model underlying the Inequity Aversion engine.
Implications of Rational Inattention
2003Christopher A. Sims · Journal of Monetary Economics
Foundational paper for the Rational Inattention model: it treats attention as a constrained information channel.
Regret Theory: An Alternative Theory of Rational Choice Under Uncertainty
1982Graham Loomes & Robert Sugden · The Economic Journal
The canonical foundation for Regret Theory: it introduces counterfactual comparison as a driver of choice under uncertainty.
Econometrica
1933Econometric Society · econometricsociety.org
Leading journal for mathematical economics and formal behavioural models.
Journal of Economic Perspectives
1987American Economic Association · aeaweb.org
Readable review articles across economics, with frequent coverage of behavioural topics.
Journal of Behavioral Decision Making
1988Wiley · Wiley Online Library
Core journal for decision research, heuristics, and behavioural biases.
Behavioural Public Policy
2017Cambridge University Press · Cambridge Core
Covers applied behavioural science in policy, including nudges, defaults, and intervention design.
Ready to run a simulation?
Open the workspace and pick a model to get started.