Walk into most HR departments today and you will find personality assessments that nobody can fully scrutinise. The items are secret. The scoring algorithms are proprietary. If a researcher wanted to replicate the findings, they could not. This is the norm — not the exception — for commercial personality instruments used in organisations.
The International Personality Item Pool (IPIP) was created specifically to break that norm.
Why Proprietary Personality Tests Are Scientific Black Boxes
The dominant personality instruments in organisational settings — the NEO PI-R (Costa & McCrae), DISC, Hogan Personality Inventory — share a structural problem: they are black boxes. The items cannot be reproduced, translated, or used in independent research without a licence. The cost of administering the NEO PI-R alone runs to approximately €15–25 per person. For a team of 50, that is a significant budget commitment for data you cannot independently verify.
This creates a replication crisis problem. If personality research published in academic journals uses proprietary instruments, other researchers cannot check the work. The findings are built on a foundation that only paying customers can inspect.
Psychometrics — the science of measuring psychological constructs — has the same standards of transparency expected in any other science. The IPIP was the movement to enforce those standards. For a broader comparison of open versus proprietary approaches, see open-source vs commercial personality tests.
What the IPIP Is and What Makes It Different
The International Personality Item Pool (ipip.ori.org) is a public-domain repository of personality items created by Lewis Goldberg at the Oregon Research Institute. First described formally in Goldberg et al. (2006), it now contains over 3,000 items measuring personality constructs across the Big Five dimensions and their facets.
Every item in the IPIP is in the public domain. There is no licence fee. There is no permission required. Anyone — a researcher, a startup, a clinician, a government agency — can use, translate, modify, and republish the items freely.
Lewis Goldberg (2006): "The goal of the IPIP project is to stimulate research on personality measurement..." — doi:10.1177/1073191106293419
How IPIP Items Are Validated Against the Big Five
IPIP items are not arbitrary questions. They are developed and validated against established personality constructs using factor analysis. Each item has documented correlations with the Big Five dimensions (Openness, Conscientiousness, Extraversion, Agreeableness, Neuroticism — called Vision, Discipline, Presence, Bond, and Depth in Cèrcol) and their 30 facets.
Two validated short-form versions are especially important for applied use:
- Johnson (2014) 120-item IPIP-NEO: A 120-item version that provides reliable facet-level measurement. doi:10.1016/j.jrp.2014.05.003
- Maples-Keller et al. (2019) 60-item version: A more concise 60-item version validated for research and applied contexts. doi:10.1037/pas0000571
Both versions demonstrate strong psychometric properties comparable to proprietary instruments — without the licence cost or the opacity. For a deeper understanding of what the dimensions measure, the articles on Discipline (Conscientiousness), Bond (Agreeableness), and Presence (Extraversion) are useful starting points.
IPIP vs NEO PI-R: Open Science vs Proprietary Licence
| Feature | IPIP | NEO PI-R | DISC |
|---|---|---|---|
| Cost | Free | ~€15–25/person | Commercial |
| Items publicly available | ✅ Yes | ❌ No | ❌ No |
| Big Five–grounded | ✅ Yes | ✅ Yes | Partial |
| Peer-reviewed validation | ✅ Extensive | ✅ Extensive | Limited |
| Can be translated freely | ✅ Yes | Restricted | Restricted |
| Can be used in research | ✅ Without permission | Requires licence | Requires licence |
| Used in Cèrcol | ✅ | ❌ | ❌ |
The NEO PI-R is a scientifically rigorous instrument. Costa and McCrae's work is well validated and well cited. But the items are proprietary. You cannot independently audit the content of what is being measured without paying for access, and you cannot build on it without a commercial licence.
The IPIP solves exactly this problem. It measures the same Big Five constructs — with comparable psychometric quality — entirely in the open.
Why Open Science Produces More Trustworthy Personality Data
Open science is not just an academic principle. For personality assessment in organisations, it has direct practical consequences:
- Auditability. When items are public, HR teams, employees, and researchers can examine what is actually being measured. There are no hidden constructs.
- Replicability. Findings from IPIP-based research can be reproduced by independent teams. Results can be challenged, extended, and confirmed.
- Equity. A free instrument means organisations of any size — a five-person startup or a multinational — can access the same validated measurement tools.
- Scientific cumulation. Because thousands of researchers worldwide use the same public items, the evidence base grows collectively. Meta-analyses like Barrick & Mount (1991) are possible precisely because researchers were using comparable, documented instruments.
The replication crisis in psychology has made clear that science built on proprietary, unauditable instruments is fragile. The IPIP is the infrastructure for personality science that can actually be replicated. To understand which IPIP-based findings have held up and which have not, see personality science and the replication crisis.
How Cèrcol Uses the IPIP for Auditable Team Assessment
Cèrcol uses IPIP items exclusively. Every question in the assessment is drawn from the public-domain IPIP item pool, selected and validated against the Big Five factor structure. The items are documented, citable, and independently verifiable.
Cèrcol's dimension names — Presence (Extraversion), Bond (Agreeableness), Vision (Openness), Discipline (Conscientiousness), Depth (Neuroticism) — are product labels for user-facing communication. The underlying constructs are the standard Big Five factors, measured with IPIP items.
The science page documents the specific items used, the scoring methodology, and what has and has not been validated. Everything is open. That is the point. To see how the IPIP fits into the broader history of the Big Five, see the history of the Big Five from Allport to Goldberg.
See the open science in action: try Cèrcol for free
The IPIP exists so that personality science can be audited, replicated, and built on — not locked behind a paywall. Cèrcol is what that principle looks like in practice: a team assessment built entirely on public-domain IPIP items, with scoring logic documented on the science page, and no licence fees for any team size.
If you want to experience an IPIP-based assessment rather than just read about one, Cèrcol is free at cercol.team. You will see your scores on all five dimensions — Vision, Discipline, Presence, Bond, Depth — grounded in the same validated item pool described in this article.
References
- Goldberg, L. R., et al. (2006). The International Personality Item Pool and the future of public-domain personality measures. Journal of Research in Personality, 40, 84–96. doi:10.1177/1073191106293419
- Johnson, J. A. (2014). Measuring thirty facets of the Five Factor Model with a 120-item public domain inventory: Development of the IPIP-NEO-120. Journal of Research in Personality, 51, 78–89. doi:10.1016/j.jrp.2014.05.003
- Maples-Keller, J. L., et al. (2019). Using item response theory to develop a 60-item representation of the NEO PI-R using the International Personality Item Pool. Psychological Assessment, 31(2), 154–164. doi:10.1037/pas0000571
- Barrick, M. R., & Mount, M. K. (1991). The Big Five personality dimensions and job performance: A meta-analysis. Personnel Psychology, 44(1), 1–26. doi:10.1111/j.1744-6570.1991.tb00688.x
Further reading
- Big Five vs DISC vs Belbin: a scientist's comparison
- What is reliability and validity in personality testing?
- Why 120 items is better than 10: the trade-off in personality test length
- How personality test scores are calculated: from items to dimensions
- Open-source vs commercial personality tests: what you're actually paying for
- The history of the Big Five: from Allport to Goldberg