What is the IPIP (International Personality Item Pool)?

What is the IPIP?

The International Personality Item Pool, usually just called the IPIP, is a large collection of personality questionnaire items that its creators placed in the public domain. Anyone can use the items, translate them, shorten them, or recombine them into a new scale and publish the result, without asking permission or paying a licence fee (Goldberg et al., 2006).

The IPIP itself is not a test you sit and get one score from. It is closer to a library, a shared set of raw material that researchers and developers draw on to build their own personality measures. The IPIP-NEO, covered below, is the best known scale built from that library, but it is one of many, and the Big Five structure it is built to measure has itself survived decades of attempts to replace it (Goldberg, 1993).

Being public domain is not itself a mark of quality. The items being public domain says something about who can use them and on what terms, not about how well any particular scale built from them performs. That has to be shown for each scale on its own evidence, the way Johnson (2014) showed it for the IPIP-NEO-120, described next.

What is the IPIP-NEO?

The IPIP-NEO is a family of scales built from the pool to measure the same five domains and 30 facets that the NEO PI-R measures (Costa & McCrae, 1992). The original version uses 300 items, several for each facet.

Johnson (2014) developed a shorter alternative, the IPIP-NEO-120, using 120 items, four for each of the 30 facets. Across two large internet samples, the 30 four-item facet scales showed acceptable reliability, and the factor structure that came out of them was nearly identical to the NEO PI-R's own structure. Facet scores from the shorter form also converged with scores from the full NEO PI-R and with ratings from people who knew the respondent well (Johnson, 2014).

Acceptable is the word the research itself supports, not perfect or equivalent to a full-length commercial instrument. A four-item facet scale is shorter than most facet scales in a commercial inventory, and the ordinary trade-off between length and precision applies here as everywhere else.

Why does it matter that the items are public domain?

Public domain removes the two costs that usually stop a personality item from travelling: a licence fee, and a decision by whoever holds the copyright about who gets to use it. Anyone building a scale, a translation, a research study, or a free online test can start from IPIP items directly, rather than negotiating for access or writing new items from scratch and validating them again from nothing.

That is the argument a group of measurement researchers made directly: that public-domain personality measures deserved a genuine chance to develop alongside, and be tested against, commercial inventories, with the IPIP offered as the working example of what that could look like (Goldberg et al., 2006).

It is also why the pool has been reused so often. The IPIP-NEO is one scale built from it. Domain-level scales, translations into other languages, and shorter forms built for a particular study exist as well, because nothing stops a researcher from assembling one and publishing it.

What structure does the IPIP-NEO mirror?

The NEO PI-R organises personality into five broad domains and, beneath each domain, six narrower facets, for 30 facets in total (Costa & McCrae, 1992). That domain-and-facet architecture is one of the more detailed maps of the Big Five in wide use, reporting something between one number per domain and one number per single trait word.

The IPIP-NEO was built to reproduce that same architecture with public-domain items rather than the NEO PI-R's own copyrighted ones, and Johnson's 120-item version reproduced it closely enough that its factor structure and facet scores lined up with the original (Johnson, 2014). Someone who takes the IPIP-NEO answers questions organised the same way a NEO PI-R respondent's are, drawn from a different set of items.

What are the main IPIP-based measures?

The pool has produced more than one instrument, and they differ mainly in length and in how much of the facet level they keep.

Two scales with the same family name are not necessarily the same instrument. Because the pool is open, anyone can describe a scale as IPIP-based after using a handful of its items in a different combination, so the item count and the facet list are worth checking before comparing a score against someone else's.

How does Wellington use IPIP items?

Wellington is a science-based personality assessment from Therabot Labs LLC. It measures personality as continuous traits, built on the Big Five and HEXACO models, and writes the results back as a personal report rather than a type.

• The item bank. Wellington's questions are public-domain IPIP items and public-domain items written in the same style, curated for a wellness setting rather than a laboratory, and each trait's methods note names the published scale it draws on. No items are licensed from a commercial inventory.
• The free Snapshot. 60 questions across 6 dimensions, Extraversion, Agreeableness, Conscientiousness, Emotional Stability, Openness to Experience and Honesty-Humility, each scored from several statements rather than one.
• The Wellington Membership. Adds 336 further questions to reach 90 traits, including every facet in the bank, for $4.99 a month.

Every trait is reported as a percentile against the reference sample. The three bands (Quiet below the 30th percentile, Balanced to the 70th, High above) and the Portrait names exist to make the result easier to talk about; the percentile is the measurement, and it is always shown alongside. Those norms are provisional while the norming sample is completed.

The Snapshot is free. The Wellington Membership is $4.99 a month, and extends coverage toward all 255 traits across eight domains, with retests in year two, and it can be cancelled any time. Wellington is a wellness tool for reflection, not a medical or psychological diagnosis, and it does not replace care from a qualified professional.

Questions people ask

Is the IPIP the same thing as the IPIP-NEO?

No. The IPIP is the whole item pool, a large public-domain resource that anyone can build a scale from. The IPIP-NEO is one particular family of scales built from that pool, designed to measure the same five domains and 30 facets as the NEO PI-R (Costa & McCrae, 1992). Other scales, covering different traits or fewer of them, have been built from the same pool.

How long is the IPIP-NEO?

The original IPIP-NEO uses 300 items to measure 30 facets with several items each. Johnson (2014) developed a shorter 120-item version, the IPIP-NEO-120, using four items per facet, and found acceptable reliability for all 30 facets and a factor structure that closely matched the NEO PI-R. Which length to use depends on how much time is available and how much facet detail is needed.

Is the IPIP-NEO as accurate as a commercial test like the NEO PI-R?

The IPIP-NEO-120 converged with NEO PI-R scores and with ratings from people who knew the respondent well, and its factor structure closely matched the NEO PI-R's own (Johnson, 2014). That is a genuinely strong result, but the published record does not establish that public-domain scales are equivalent to commercial inventories in every respect, so it is fairer to say the two measure the same structure closely rather than identically.

Can anyone use IPIP items for free?

Yes. Being in the public domain means the items carry no licence fee and no requirement to ask permission before using, translating, shortening, or recombining them into a new scale (Goldberg et al., 2006). That is the point of the project: personality measurement that does not depend on paying a publisher for access to the questions themselves.

Does Wellington use IPIP items?

Yes. The statements Wellington asks are public-domain IPIP items, together with public-domain items written in the same style, curated for a wellness setting, and every trait's methods note names the published scale it draws on. Each trait is measured with several statements rather than one, and the free Snapshot uses 60 of them.