Abstract
Dishonest behaviours such as tax evasion impose significant societal costs. Ex ante honesty oaths—commitments to honesty before action—have been proposed as interventions to counteract dishonest behaviour, but the heterogeneity in findings across operationalizations calls their effectiveness into question. We tested 21 honesty oaths (including a baseline oath)—proposed, evaluated and selected by 44 expert researchers—and a no-oath condition in a megastudy involving 21,506 UK and US participants from Prolific.com who played an incentivized tax evasion game online. Of the 21 interventions, 10 significantly improved tax compliance by 4.5 to 8.5 percentage points, with the most successful nearly halving tax evasion. Limited evidence for moderators was found. Experts and laypeople failed to predict the most effective interventions, though experts’ predictions were more accurate. In conclusion, honesty oaths were effective in curbing dishonesty, but their effectiveness varied depending on content. These findings can help design impactful interventions to curb dishonesty.
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Data availability
The datasets generated by the survey research and/or analysed during the current study are available via Zenodo at https://doi.org/10.5281/zenodo.13329833 (ref. 80) and at https://osf.io/t3sm4/ (pilot studies)81.
Code availability
All code used to generate the main and supplementary analyses is available in the osf.io repository at https://osf.io/t3sm4/ and via Zenodo at https://doi.org/10.5281/zenodo.13329833 (ref. 80). We used R (version 4.2.1; ref. 82) and the R packages broom (version 1.0.4; ref. 83), dplyr (version 1.1.1; ref. 84), ggplot2 (version 3.4.4; ref. 85), ggpubr (version 0.4.0; ref. 86), glmmTMB (version 1.1.7; ref. 87), janitor (version 2.1.0; ref. 88), lme4 (version 1.1-32; ref. 89), marginaleffects (version 0.14.0; ref. 90), meta.shrinkage (version 0.1.4; ref. 91), papaja (version 0.1.1; ref. 92), purrr (version 1.0.1; ref. 93), psych (version 2.2.5; ref. 94), qualtRics (version 3.1.7; ref. 95), sjPlot (version 2.8.14; ref. 96), stringr (version 1.5.0; ref. 97), tidyverse (version 1.3.2; ref. 98), TOSTER (version 0.8.0; ref. 38) and mice (version 3.16.0; ref. 99) for our analyses.
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Acknowledgements
P.M. was supported by grant no. AUFF-E-2019-9-4 NOVA. Y.F. was supported by ERC grant no. 101054656 (project acronym VCOMP). E.P. and Y.F. were supported by a grant from the Israeli Science Foundation Award No. 385/20. A.Z.C. was supported by grant no. 2018/30/E/HS6/00863 from the National Science Center, Poland. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. We thank P. Nickl for input on visualizations.
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Conceptualization: J.H.Z. and P.M. Data curation: J.H.Z. Formal analysis: J.H.Z. Funding acquisition: J.M., D.A., I.T., S.H., A.-K.K., S.P. and P.M. Investigation: J.H.Z. Methodology: J.H.Z., K.A.Ś., C.T.E., J.M., M.H.T., G.L., S.A., E.P., E.C., U.G., S. Schudy, Y.F., P.K., N.M., S. Schindler, A.W., D.N., V.C., R.H., R.B., D.A., R.M.-R., I.T., J.B.M., P.G., Š.B., M.B., J.K.W., L.N., S.B., N.J., N.K., S.H., Z.R., A.K., Y.A.N., A.-K.K., M.V., A.Z.C., A.S., S.P. and P.M. Project administration: J.H.Z. Validation: J.H.Z., E.P., J.B.M. and Y.A.N. Visualization: J.H.Z. and Z.R. Writing—original draft: J.H.Z. Writing—review and editing: J.H.Z., K.A.Ś., C.T.E., J.M., M.H.T., G.L., S.A., E.P., E.C., U.G., S. Schudy, Y.F., P.K., N.M., S. Schindler, A.W., D.N., V.C., R.H., R.B., D.A., R.M.-R., I.T., J.B.M., P.G., Š.B., M.B., J.K.W., L.N., S.B., N.J., N.K., S.H., Z.R., A.K., Y.A.N., A.-K.K., M.V., A.Z.C., A.S., S.P. and P.M. The authorship order for the first seven and last two authors was set a priori. The authorship order for the remaining authors was determined randomly.
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Zickfeld, J.H., Ścigała, K.A., Elbæk, C.T. et al. Effectiveness of ex ante honesty oaths in reducing dishonesty depends on content. Nat Hum Behav 9, 169–187 (2025). https://doi.org/10.1038/s41562-024-02009-0
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DOI: https://doi.org/10.1038/s41562-024-02009-0
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