HEXACO-TI: Proposal for a New Personality Test That Combines the HEXACO Model of Personality With the MBTI Letter System

IMAGE (ABOVE): A concept logo for the proposed test, combined with artwork from 16 Personalities.

Executive Summary

Many of the personality tests that are currently available to the public are based on the Five-Factor Model of Personality (FFM) or the Myers-Briggs Type Indicator (MBTI). One of the most popular of these personality tests — the NERIS Type Explorer — combines these two personality systems into one. However, in recent years, a new model — the HEXACO Model of Personality — which adds a sixth personality trait (i.e., honesty-humility), has gained substantial empirical support. This means that many of the currently available personality tests are missing an important personality trait, one that would be valuable for individuals and organisations to measure. Therefore, I propose a new personality test which combines the HEXACO Model of Personality with an MBTI-like letter system. The reliability of the test would be assessed through inspecting the internal consistency for each personality trait, and through test-retest reliability across three occasions at monthly intervals. The validity of the test would be assessed through investigating the content validity, the convergent validity (by comparing the measures with other similar scales), and the criterion validity of the honesty-humility scale (by comparing a general sample with a clinical sample known to be low in honesty-humility).

Aims and Significance

In recent decades, personality testing has become a popular means for individuals to improve self-understanding and interpersonal relationships (Druckman & Bjork, 1991), and for organisations to improve employee selection, since personality tests have been shown to predict job performance in a variety of domains (Barrick & Mount, 2016; Sackett & Walmsley, 2014; Tett & Christiansen, 2007). Unfortunately, there are wide variety of personality tests with varying theoretical or empirical bases to choose from, with their own strengths and weaknesses (Matz et al., 2016), potentially making it difficult to know which to choose. The most widely accepted of these tests is the FFM. However, this model is lacking a personality trait (i.e., honesty-humility) that has been found to be important (Ashton & Lee, 2007). It also lacks the benefits of a model like the MBTI which helps make personality differences more easily understood by the public (McCrae & Costa, 1989). The proposed model would integrate the benefits of MBTI with HEXACO, the model of personality which has extended the FFM to include the honesty-humility personality trait (Ashton & Lee, 2007). Doing so would combine the advantages of using a more predictive personality system (Pletzer et al. 2019; Soutter et al., 2020), with the advantages of MBTI in making personality traits more easily understood and communicable to the public.

“The MBTI was developed by Isabel Briggs Myers and Katharine Cook Briggs, and is based on Carl Jung’s theory of psychological types. This theory proposes four primary types of “psychological functions” (now commonly referred to as cognitive functions) which each have an introverted and extraverted variation, resulting in eight total functions.”

Background

The MBTI was developed by Isabel Briggs Myers and Katharine Cook Briggs (Matz et al., 2016), and is based on Carl Jung’s (1921) theory of psychological types. This theory proposes four primary types of “psychological functions” (now commonly referred to as cognitive functions) which each have an introverted and extraverted variation, resulting in eight total functions, shown in Table 1 (Berens & Nardi, 2004). Myers and Briggs took Jung’s cognitive function constructs and developed them into a system of 16 personality types, indicated by two possible letter options for a four-letter combination (i.e., I/E = introversion/extraversion, S/N = sensing/intuitive, T/F = thinking/feeling, P/J = perceiving/judging; e.g., ISTP; Myers & Myers, 1980). MBTI is deemed to be clinically and practically useful for understanding differences in behaviour (Meunier, 2011; Osmond, 1977), and useful for making personality differences understood by the public (Druckman & Bjork, 1991; McCrae & Costa, 1989). Despite this, Jungian cognitive functions have been difficult to operationalise and demonstrate empirically (16 Personalities, n.d.; Boyle, 1995, Davis & Mattoon, 2006). And several studies aiming to replicate the factor structure of MBTI have unable to do so, calling into question the validity of MBTI (Pittenger, 1993). It has also been found to be poorly predictive of real-life outcomes, further calling into question its validity (Matz et al., 2016).

“Recognising the various problems with MBTI, but also its benefits, led the creators of the FFM, Robert McCrae and Paul Costa, to propose that MBTI be reinterpreted and integrated with the FFM.”

Recognising the various problems with MBTI, but also its benefits, led the creators of the FFM, Robert McCrae and Paul Costa (1989), to propose that MBTI be reinterpreted and integrated with the FFM. This is because, unlike MBTI, the FFM has been found to be stable across cultures (McCrae & Allik, 2002), across instruments and observers (McCrae & Costa, 1987), and is predictive of real-life outcomes (Ozer & Benet-Martínez, 2006). Combining the FFM with MBTI is what the NERIS Type Explorer has done (16 Personalities, n.d.). But, instead of Jungian cognitive functions, the NERIS Type Explorer uses the FFM to assign a corresponding letter on each of the five dimensions to result in a personality type. For example, results consistent with being high in extraversion would result in being assigned “E”, and low with “I”. One factor of the FFM that is not captured by the MBTI is neuroticism. The NERIS Type Explorer addresses this by adding an additional letter onto the end of the MBTI letter combination, separated by a hyphen (i.e., A/T = assertive/turbulent, where “A” indicates low neuroticism and “T” indicates high neuroticism; e.g., ISTP-A). Even though it is based on the FFM, the NERIS Type Explorer has also been independently validated in a variety of ways, including factor analysis (16 Personalities, n.d.; Kirti & Govind, 2020).

“…the addition of the honesty-humility factor…enables the model to predict phenomena that the FFM cannot account for, and be even more predictive than the FFM in a wide range of domains.”

Despite the FFM being the current dominant model, a new similar model called the HEXACO Model of Personality has been developed (Matz et al., 2016). Although there are some subtle differences between the FFM and HEXACO, the main difference is the addition of the honesty-humility factor, to create a total of six personality factors. This additional factor enables the model to predict phenomena that the FFM cannot account for (Ashton & Lee, 2007), and be even more predictive than the FFM in a wide range of domains. For example, workplace deviance (Pletzer et al. 2019), and environmental behaviours (Soutter et al., 2020). HEXACO has also been validated across many cultures (Boies et al., 2004; de Vries et al., 2008; Međedović et al., 2019; Ørnfjord, 2018; Romero et al., 2015; Tatar, 2018; Thielmann et al., 2019; Wakabayashi, 2014). It also has high internal consistency and convergent validities with other variables (Lee & Ashton, 2004), and is consistent with biological theories (Ashton & Lee, 2001). HEXACO’s trait of honesty-humility could be integrated into an MBTI-like letter system by adding an additional letter onto the letter system used by the NERIS Type Explorer (i.e., P/H = proud/humble, where “P” indicates low honesty-humility and “H” indicates high honesty-humility; e.g., ISTP-AP). Correlations between MBTI equivalents in the FFM, and the FFM equivalents in HEXACO are shown in Table 2.

Proposed Test & Rationale

Therefore, I propose that a new personality test is developed, one that is like the NERIS Type Explorer, but instead of combining the FFM and MBTI, the new test would combine HEXACO and MBTI. The traits of the HEXACO Model of Personality are honesty-humility, emotionality, extraversion, agreeableness, conscientiousness, and openness to experience (Lee & Ashton, 2007). Honesty-humility is measuring the construct of fairness, where low levels are associated with narcissism, Machiavellianism, and psychopathy (i.e., the “dark triad”; Lee & Ashton, 2005). Emotionality is measuring the construct of kin altruism (Lee & Ashton, 2007). Extraversion is measuring the construct of engagement in social endeavours. Agreeableness is measuring the construct of reciprocal altruism. Conscientiousness is measuring the construct of engagement in task-related endeavours. And openness to experience is measuring the construct of engagement in idea-related endeavours. By combining HEXACO and the letter system of MBTI, I seek to create a test that has the advantages of using an empirically supported and predictive model of personality, while also having the advantage of creating a series of personality “types” that make the information more easily comprehendible, facilitating greater self-understanding and the understanding of others, and potentially leading to the better communication of needs and interpersonal relationships. The test would be beneficial to individuals seeking self-discovery and organizations seeking to increase workplace harmony.

IMAGE (ABOVE): Artwork from 16 Personalities edited to include the additional honesty-humility personality trait from the HEXACO Model of Personality.

Study Design

Two groups of participants would be required, a general sample, and a clinical sample. The general sample would include 1,000 participants and be recruited from the online participant recruitment site Prolific, which is commonly used as a method of participant recruitment for research in social psychology. Prolific participants would be reimbursed at £5.00/$6.00USD/$9.00AUD per hour for each questionnaire they complete. The clinical sample would be recruited through the clients of psychology clinics who have been diagnosed using the American Psychiatric Association (2013) diagnoses of narcissistic and/or antisocial personality disorders, since the traits of these conditions are consistent with low levels of honesty-humility (Lee & Ashton, 2005; Perrson, 2019). All participation would be voluntary, and participants would be informed that they can withdraw from the study at any time without penalty.

Design and Procedure

The study will use a two-condition (general sample vs. clinical sample) between-groups design. Participants would complete an online questionnaire containing the below measurement scales on three occasions, separated by monthly intervals, and submit their results.

Measures

Demographic — Demographic variables (e.g., age, gender, race/ethnicity) would be measured, to ensure that the general sample is representative of the general population.

Honesty-Humility — Ten items would be adapted from Ashton and Lee (2009) to measure honesty-humility (e.g., “I would never accept a bribe, even if it were very large”). Responses to the ten corresponding items would be recorded on a 5-point Likert scale (1 = strongly disagree, 5 = strongly agree), and then averaged, where higher scores indicate greater honesty-humility. Scores above 50% would be allocated a humility preference (indicated by the letter “H”), and below 50% would be allocated a pride preference (indicated by the letter “P”).

Emotionality — Ten items would be adapted from Ashton and Lee (2009) to measure emotionality (e.g., “I feel like crying when I see other people crying”). Responses to the ten corresponding items would be recorded on a 5-point Likert scale (1 = strongly disagree, 5 = strongly agree), and then averaged, where higher scores indicate greater emotionality. Scores above 50% would be allocated a turbulent preference (indicated by the letter “T”), and below 50% would be allocated an assertive preference (indicated by the letter “A”).

Extraversion — Ten items will be adapted from Ashton and Lee (2009) to measure extraversion (e.g., “I feel reasonably satisfied with myself overall”). Responses to the ten corresponding items would be recorded on a 5-point Likert scale (1 = strongly disagree, 5 = strongly agree), and then averaged, where higher scores indicate greater extraversion. Scores above 50% would be allocated an extraversion preference (indicated by the letter “E”), and below 50% would be allocated an introversion preference (indicated by the letter “I”).

Agreeableness — Ten items would be adapted from Ashton and Lee (2009) to measure agreeableness (e.g., “I tend to be lenient in judging other people”). Responses to the ten corresponding items would be recorded on a 5-point Likert scale (1 = strongly disagree, 5 = strongly agree), and then averaged, where higher scores indicate greater agreeableness. Scores above 50% would be allocated a feeling preference (indicated by the letter “F”), and below 50% would be allocated a thinking preference (indicated by the letter “T”).

Conscientiousness — Ten items would be adapted from Ashton and Lee (2009) to measure conscientiousness (e.g., “People often call me a perfectionist”). Responses to the ten corresponding items would be recorded on a 5-point Likert scale (1 = strongly disagree, 5 = strongly agree), and then averaged, where higher scores indicate greater conscientiousness. Scores above 50% would be allocated a judging preference (indicated by the letter “J”), and below 50% would be allocated a perceiving preference (indicated by the letter “P”).

Openness to Experience — Ten items would be adapted from Ashton and Lee (2009) to measure openness to experience (e.g., “People have often told me that I have a good imagination”). Responses to the ten corresponding items would be recorded on a 5-point Likert scale (1 = strongly disagree, 5 = strongly agree), and then averaged, where higher scores indicate greater openness to experience. Scores above 50% would be allocated an intuitive preference (indicated by the letter “N”), and below 50% would be allocated a sensing preference (indicated by the letter “S”).

Test Evaluation: Assessment of Reliability and Validity

Reliability Assessment

To assess the reliability of the scales, internal consistency and test-retest reliability would be implemented. The internal consistency of the scales will be measured using Conbach’s alpha. A value above .70 would be required to establish adequate internal reliability for the scales. Because the personality traits of an individual are stable over the course of their lifespan (Tardiff, 2009), completing the test multiple times would not be subject to practice effects. Therefore, scores that are strongly positively correlated across several testing times would demonstrate sufficient test-retest reliability.

Validity Assessment

To assess the validity of the scales, an estimate of content validity, as well as the convergent validity, and criterion validity (of the honesty-humility scale) would be implemented. Content validity would be assessed by seeking out a range of experts who have worked with the HEXACO Model of Personality (Ashton & Lee, 2007) and asking their opinions on the developed scales. A consensus of the scales being acceptable among these experts would be considered sufficient grounds for the scales having content validity.

The convergent validity of the scales would be assessed by correlating them with their relevant counterparts in the HEXACO, FFM, and MBTI personality systems. Previous studies have found that there are moderate to strong correlations between the HEXACO and FFM (Ashton et al., 2014; Biderman et al., 2019; Lee & Ashton, 2004; Lee et al., 2005), and between the FFM and MBTI (MacDonald et al., 1994; McCrae & Costa, 1989). Results consistent with moderate to strong correlations between the developed scales and the scales of HEXACO, FFM, and MBTI (depending on how similar the specific scales would be expected to be) would demonstrate sufficient convergent validity.

The criterion validity of the honesty-humility scale would be assessed using the method of contrasted groups. The criterion validity of the other personality dimensions will not be assessed at this time since the validity of comparable scales have been tested extensively (e.g., McCabe et al., 2021; Moberg, 1998; Pletzer et al., 2019; Salgado, 2003). Muris and colleagues (2017) conducted a meta-analysis and found that honesty-humility is associated with narcissism, Machiavellianism, and psychopathy (i.e., the “dark triad”) with moderate to large negative correlations, such that lower scores of honesty-humility are associated with higher levels of “dark triad” traits. Therefore, if the new honesty-humility scale is valid, those clinically diagnosed with “dark triad” traits should score lower on this item than the general sample. To determine whether these groups are significantly different, independent groups t-tests would be used. A significant difference would demonstrate sufficient criterion validity of the honesty-humility scale.

Conclusion

In conclusion, the creation of a new personality test which combines the benefits of the HEXACO Model of Personality with the benefits of the MBTI letter system, would provide a test that is of greater benefit to both individuals and organisations than the other currently available personality tests. This would enable even greater understanding of the self and others, and likely facilitate greater social harmony in both personal and work environments. Because of this, the creation and validation of this new test would create a product that has the potential to exceed the popularity of the already incredibly popular NERIS Type Explorer.

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