A Critical Look at the Enneagram Test
A Critical Look at the Enneagram Test: Nine Types, a Comforting Myth
A Critical Look at the Enneagram Test: Nine Types, a Comforting Myth
DESCRIPTION: The Enneagram promises self-knowledge through nine types and feels accurate to many people. This is down to the Barnum effect, not science.
Nine pigeonholes for the self: the Enneagram and the art of believing in oneself
The Enneagram divides humanity into nine types and seems to strike right at the heart of the matter. The reason for this perceived accuracy lies in an old psychological trick: the Barnum or Forer effect, named after an experiment from 1948. This article explains what the Enneagram claims, where it comes from and why it fails to stand up to the rigours of empirical science. It also asks what happens to us when we voluntarily label ourselves.
The Enneagram promises self-knowledge across nine distinct categories.
Hardly any other typology has enjoyed such a triumphant rise over the past two decades. The Enneagram classifies every person into one of nine personality types, arranged on a circle with a nonagon inscribed within it. Anyone who completes an Enneagram test receives, at the end, a number from one to nine, along with a whole host of interpretations about their own motivations, behavioural patterns and hidden fears. For many, this feels like an X-ray of the soul.
The appeal is obvious. At a time when modern life has become confusing, the Enneagram offers a system of classification that anyone can use in a matter of minutes. It requires no prior knowledge or therapy, yet still provides the feeling of finally being understood. It is precisely this feeling that is the real product. How it comes about can be described in detail.
The nine types are said to consist of a core motivation and an underlying fear.
At the heart of every Enneagram description lies the idea of a core motivation and an underlying basic fear. Type 1 is regarded as the perfectionist, driven by the desire to be good and right, and by the fear of being flawed or corrupt. Type 2, the caring helper, wants to be loved and fears being unloved and useless. Type 3 seeks success and recognition, Type 4 longs for uniqueness and identity, and Type 5 for knowledge and solitude. Next comes Type 6, the loyal security-seeker, who needs stability and reliability; Type 7, the life-loving enthusiast, who wants to avoid pain and boredom; and Type 8, the assertive protector, for whom control and strength are paramount. Finally, Type 9, the peace-loving mediator, seeks inner and outer peace and shuns conflict. Nine motives, nine fears, and supposedly every person fits into exactly one of these categories.
This is where the real allure lies. The descriptions are structured in such a way that people categorise themselves based on their own feelings. Anyone who recognises themselves in Type 4 has usually chosen that type themselves, because the wording resonated sufficiently with them. An empirically validated measurement tool looks quite different.
Wings and arrows make the system appear precise and, in fact, irrefutable.
To ensure the nine types can account for the diversity of real people, the Enneagram has incorporated two extensions. The first are the wings: each type borrows characteristics from one of its two neighbours on the circle. A Type 5 may have a Four wing or a Six wing, and as a result appears either more dreamy or more anxious. This means that the nine types can give rise to significantly more variants.
The second extension consists of the arrows, often referred to as integration and disintegration. Under stress, a type is said to move along a line towards another type and adopt that type’s unhealthy traits. When feeling secure and mature, they move in the opposite direction and display the healthy aspects of another type. A stressed Type 1 is said to display the impulsive traits of Type 4, whilst a mature Type 1 displays the serenity of Type 7.
What at first glance looks like a subtle distinction is, in reality, a defence mechanism against any refutation. If a behaviour does not fit one’s own type, it was simply the wing or the direction of stress. In this way, any observation can be retroactively categorised, and a system that explains everything ultimately explains nothing. Its irrefutability is the system’s fundamental flaw.
The origins of the Enneagram lie in esotericism.
The history of the model does not begin in psychology. The Enneagram symbol first appeared in the early twentieth century with the Armenian-Greek mystic Georg Ivanovich Gurdjieff, who taught it as a cosmological figure and whose sources remained a mystery even to his own disciples. For Gurdjieff, the symbol had nothing to do with personality types. It was an esoteric diagram depicting processes and the laws of the universe.
It was not until the 1960s that the Bolivian esotericist Oscar Ichazo, at his Arica School, linked the symbol to psychological meanings and assigned human passions and fixations to the nine points. In the early 1970s, the Chilean psychiatrist Claudio Naranjo travelled to Arica, adopted the basic idea and translated it into the language of personality psychology and psychoanalysis. Naranjo coined the type descriptions as we know them today and disseminated them through seminars in California.
This origin is not a flaw in itself, but it is revealing. The nine types were established by individual thinkers, based on intuition, self-observation and spiritual tradition. Experts refer to this as a ‘top-down’ projection: first the structure was established, then people were interpreted within it. An empirical model is developed in the opposite direction.
The Barnum effect is the real driving force behind the perceived accuracy.
So why does the Enneagram seem to be so accurate? The answer was provided by the psychologist Bertram Forer as early as 1948. He gave his students a personality test and afterwards handed each of them a supposedly personalised assessment. In reality, they all received the same text, cobbled together from sentences in a cheap astrology magazine bought from a newsagent’s. The students were asked to rate, on a scale of one to five, how well the description applied to them. The average score was 4.3.
The sentences worked because they were vague and universally human. Statements such as ‘You have a strong need to be liked by others’ or ‘Sometimes you doubt whether you have made the right decision’ apply to almost everyone. Forer initially called this phenomenon the ‘personal validation fallacy’. Today it is known as the Barnum or Forer effect. The experiment has been repeated hundreds of times over the past 75 years, across different cultures and formats, and the mean score remains stable at around 4.2.
Enneagram descriptions are structured precisely along these lines. They combine broadly relatable observations with a flattering, in-depth interpretation. The effect is amplified when the text sounds predominantly positive and when the source is perceived as reputable and well-meaning. The coaching language of the Enneagram effortlessly fulfils both conditions.
Without the reader, the text would be empty: confirmation bias completes the illusion.
The Barnum effect alone generates agreement. This is transformed into a firm conviction by confirmation bias. Once someone sees themselves as a Type 2, they will henceforth tend to collect those memories and everyday scenes that fit the image of the caring helper, whilst overlooking the counterexamples. Over the course of weeks, a vague description thus becomes a perceived truth that is reinforced daily.
Added to this is the reader’s active role in interpretation. The Enneagram provides the framework; the individual fills it with their own life story. A sentence about ‘the need for authenticity’ becomes, for one person, a memory of a courageous decision to resign, and for another, a lament about an unsuitable relationship. The text remains the same; the perceived fit arises in the mind. The accuracy attributed to the model is one’s own achievement, which one merely lends to it.
Empirically, the Enneagram does not stand up to standard tests
A personality model must clear two hurdles. Reliability means that a test yields stable results when administered repeatedly. Validity means that it actually measures what it purports to measure, and that the postulated categories are reflected in the data. In the case of the Enneagram, the research evidence is sparse and sobering.
A systematic review published in 2020 examined the available research across numerous samples. Its conclusion is mixed to sceptical. Factor analysis studies consistently found fewer than nine independent dimensions, and no study was able to reconstruct the nine types from the data using cluster analysis methods. In other words: if you break down the responses statistically, the nine distinct types do not emerge. They are an arbitrary classification.
A personality researcher summarises the verdict in Inverse magazine by stating that the Enneagram is ‘pseudoscientific at best’. What this means is that the hallmarks of scientific measurement are missing: verifiable predictions, empirically derived categories and the fundamental possibility that the model could be discredited by reality. This is not to say that no one recognises any truth in it. Immunity to any refutation is one of the classic hallmarks of pseudoscience.
Even the scientific benchmark is less solid than one might think.
In discussions about the Enneagram, the Five-Factor Model – the Big Five – is often cited as a reputable counter-check. This model is indeed better substantiated, but it is only of limited use as a ‘gold standard’ against which everything can be measured. The Big Five are derived purely descriptively from statistical analysis of linguistic data; they are a by-product of factor analysis without any underlying theory as to why these five dimensions in particular should exist. They describe surface-level patterns; they do not explain anything.
Their claimed universal validity is also fragile. A large proportion of the underlying research stems from so-called WEIRD samples – from Western, educated, industrialised, rich and democratic societies. Where the model was tested outside this bubble, it fell apart. The 2013 study by Gurven and colleagues failed to replicate the five factors among the Tsimane, an indigenous community in the Bolivian Amazon. In 2019, Laajaj and colleagues confirmed, using data from 23 low-income countries, that the familiar five-factor structure cannot be clearly replicated there.
This does not exonerate the Enneagram; it shifts the perspective. Even the most reputable personality models should be interpreted with greater caution than self-help literature suggests. If even the best available framework is culturally limited and theoretically hollow, a system that derives its nine types from esoteric tradition should certainly be treated with even greater caution.
An industry has grown up around the Enneagram that thrives on interpretation.
The Enneagram has long since become a market. A wide-ranging industry has formed around the nine types: paid Enneagram tests online, certification courses, books, podcasts, team workshops and coaching programmes for professional personal development. Companies book seminars to categorise their workforce by type, and entire consultancy practices build their business on the promise of self-awareness through the Enneagram.
This commercial dynamic explains much of the system’s enduring popularity. A product that immediately provides everyone with a positive ‘aha’ moment sells exceptionally well, regardless of its empirical basis. The Barnum effect is the perfect business model: the product proves its worth in the customer’s experience because the customer does the crucial work themselves. Criticism of its validity rolls off this experience, because it simply feels right.
Problems arise when the entertaining self-test becomes a tool for control. When managers allocate tasks according to Enneagram types or job applicants are assessed based on their number, an unproven typology gains real power over people’s life paths. A model that does not stand up to scientific scrutiny should not underpin such decisions.
Why an entire culture resorts to ready-made pigeonholes
More interesting than the question of whether the Enneagram is accurate is the question of why so many people want to believe in it. The longing to be a particular type is a longing for relief. Anyone who knows they are a Four no longer has to endure the agonising openness of their own existence. The self is transformed from a task into a diagnosis, from something that must be painstakingly shaped into something that needs to be looked up. In an age of constant self-optimisation, this is an understandable desire.
From a psychoanalytical perspective, this categorisation serves a dual function. It creates identity by casting a diffuse sense of self into a definable form, and it alleviates the fear of one’s own contradictions. This leads to an impoverishment. Anyone who identifies with a number confuses a snapshot with their true nature and begins to adapt their behaviour to fit the label. ‘I was classified as Type 1 in the test’ becomes ‘That is just the way I am’, and the pigeonhole that began as an explanation becomes a shackle.
Self-knowledge worthy of the name works differently. It withstands the tension inherent in the fact that a person is ambiguous, changeable and never fully described. The Enneagram offers the opposite: an immediate, flattering, definitive answer. This is precisely where its comfort lies, and this is precisely where its limitation lies. Anyone who wants to get to know themselves will eventually have to leave the nine doors behind.
The essentials in brief
• The Enneagram classifies people into nine personality types, each with a core motivation and a fundamental fear, supplemented by wings and the arrows of integration and disintegration.
• Its origins are esoteric: the symbol comes from Gurdjieff, whilst the psychological interpretation is by Oscar Ichazo and Claudio Naranjo. The nine types were established; they were not derived from data.
• The perceived accuracy is generated by the Barnum or Forer effect (Forer 1948): vague, general human statements in which almost everyone recognises themselves. The confirmation bias reinforces this belief.
• Empirically, it lacks reliability and validity. Factor analyses identify fewer than nine dimensions, whilst cluster analyses fail to reconstruct the nine types. Experts describe the model as pseudoscientific.
• Even the commonly used benchmark, the Big Five, is theoretically empty and culturally limited (WEIRD samples; Gurven et al. 2013; Laajaj et al. 2019), and is therefore of only limited use as a gold standard.
• A coaching industry has grown up around the Enneagram, whose business is based on the immediate ‘aha’ moment. As a tool for guidance in the workplace and in recruitment, an untested type model is dangerous.
• The real question is a cultural one: the longing for a ‘type’ is a longing for relief from the openness of one’s own self.
Sources
• Forer, B. R. (1949). The fallacy of personal validation: A classroom demonstration of gullibility. Journal of Abnormal and Social Psychology, 44(1), 118–123. Summary: Barnum effect (Wikipedia); Bertram Forer (Wikipedia)
• Hook, J. N. et al. (2021). The Enneagram: A systematic review of the literature and directions for future research. Journal of Clinical Psychology. PubMed 33332604
• Anthes, E. (2021). Enneagram personality test: Why experts say it is ‘pseudoscientific at best’. Inverse. inverse.com
• Whitaker, K.: What’s Wrong with the Enneagram. Useful Tool or Pseudoscientific Fad? Medium
• On its origins: A Short and Comprehensive History of the Enneagram’s Origins (Gurdjieff, Ichazo, Naranjo). integrative9.com
• Gurven, M. et al. (2013). How universal is the Big Five? Testing the five-factor model of personality variation among forager-farmers in the Bolivian Amazon (Tsimane). Journal of Personality and Social Psychology. PubMed 23245291
• Laajaj, R. et al. (2019). Challenges to capturing the Big Five personality traits in non-WEIRD populations. Science Advances, 5(7). science.org
• On the Forer effect and its replication: EBSCO Research Starters, Barnum effect. ebsco.com
Related:
DESCRIPTION: The Enneagram promises self-knowledge through nine types and feels accurate to many people. This is down to the Barnum effect, not science.
Nine pigeonholes for the self: the Enneagram and the art of believing in oneself
The Enneagram divides humanity into nine types and seems to strike right at the heart of the matter. The reason for this perceived accuracy lies in an old psychological trick: the Barnum or Forer effect, named after an experiment from 1948. This article explains what the Enneagram claims, where it comes from and why it fails to stand up to the rigours of empirical science. It also asks what happens to us when we voluntarily label ourselves.
The Enneagram promises self-knowledge across nine distinct categories.
Hardly any other typology has enjoyed such a triumphant rise over the past two decades. The Enneagram classifies every person into one of nine personality types, arranged on a circle with a nonagon inscribed within it. Anyone who completes an Enneagram test receives, at the end, a number from one to nine, along with a whole host of interpretations about their own motivations, behavioural patterns and hidden fears. For many, this feels like an X-ray of the soul.
The appeal is obvious. At a time when modern life has become confusing, the Enneagram offers a system of classification that anyone can use in a matter of minutes. It requires no prior knowledge or therapy, yet still provides the feeling of finally being understood. It is precisely this feeling that is the real product. How it comes about can be described in detail.
The nine types are said to consist of a core motivation and an underlying fear.
At the heart of every Enneagram description lies the idea of a core motivation and an underlying basic fear. Type 1 is regarded as the perfectionist, driven by the desire to be good and right, and by the fear of being flawed or corrupt. Type 2, the caring helper, wants to be loved and fears being unloved and useless. Type 3 seeks success and recognition, Type 4 longs for uniqueness and identity, and Type 5 for knowledge and solitude. Next comes Type 6, the loyal security-seeker, who needs stability and reliability; Type 7, the life-loving enthusiast, who wants to avoid pain and boredom; and Type 8, the assertive protector, for whom control and strength are paramount. Finally, Type 9, the peace-loving mediator, seeks inner and outer peace and shuns conflict. Nine motives, nine fears, and supposedly every person fits into exactly one of these categories.
This is where the real allure lies. The descriptions are structured in such a way that people categorise themselves based on their own feelings. Anyone who recognises themselves in Type 4 has usually chosen that type themselves, because the wording resonated sufficiently with them. An empirically validated measurement tool looks quite different.
Wings and arrows make the system appear precise and, in fact, irrefutable.
To ensure the nine types can account for the diversity of real people, the Enneagram has incorporated two extensions. The first are the wings: each type borrows characteristics from one of its two neighbours on the circle. A Type 5 may have a Four wing or a Six wing, and as a result appears either more dreamy or more anxious. This means that the nine types can give rise to significantly more variants.
The second extension consists of the arrows, often referred to as integration and disintegration. Under stress, a type is said to move along a line towards another type and adopt that type’s unhealthy traits. When feeling secure and mature, they move in the opposite direction and display the healthy aspects of another type. A stressed Type 1 is said to display the impulsive traits of Type 4, whilst a mature Type 1 displays the serenity of Type 7.
What at first glance looks like a subtle distinction is, in reality, a defence mechanism against any refutation. If a behaviour does not fit one’s own type, it was simply the wing or the direction of stress. In this way, any observation can be retroactively categorised, and a system that explains everything ultimately explains nothing. Its irrefutability is the system’s fundamental flaw.
The origins of the Enneagram lie in esotericism.
The history of the model does not begin in psychology. The Enneagram symbol first appeared in the early twentieth century with the Armenian-Greek mystic Georg Ivanovich Gurdjieff, who taught it as a cosmological figure and whose sources remained a mystery even to his own disciples. For Gurdjieff, the symbol had nothing to do with personality types. It was an esoteric diagram depicting processes and the laws of the universe.
It was not until the 1960s that the Bolivian esotericist Oscar Ichazo, at his Arica School, linked the symbol to psychological meanings and assigned human passions and fixations to the nine points. In the early 1970s, the Chilean psychiatrist Claudio Naranjo travelled to Arica, adopted the basic idea and translated it into the language of personality psychology and psychoanalysis. Naranjo coined the type descriptions as we know them today and disseminated them through seminars in California.
This origin is not a flaw in itself, but it is revealing. The nine types were established by individual thinkers, based on intuition, self-observation and spiritual tradition. Experts refer to this as a ‘top-down’ projection: first the structure was established, then people were interpreted within it. An empirical model is developed in the opposite direction.
The Barnum effect is the real driving force behind the perceived accuracy.
So why does the Enneagram seem to be so accurate? The answer was provided by the psychologist Bertram Forer as early as 1948. He gave his students a personality test and afterwards handed each of them a supposedly personalised assessment. In reality, they all received the same text, cobbled together from sentences in a cheap astrology magazine bought from a newsagent’s. The students were asked to rate, on a scale of one to five, how well the description applied to them. The average score was 4.3.
The sentences worked because they were vague and universally human. Statements such as ‘You have a strong need to be liked by others’ or ‘Sometimes you doubt whether you have made the right decision’ apply to almost everyone. Forer initially called this phenomenon the ‘personal validation fallacy’. Today it is known as the Barnum or Forer effect. The experiment has been repeated hundreds of times over the past 75 years, across different cultures and formats, and the mean score remains stable at around 4.2.
Enneagram descriptions are structured precisely along these lines. They combine broadly relatable observations with a flattering, in-depth interpretation. The effect is amplified when the text sounds predominantly positive and when the source is perceived as reputable and well-meaning. The coaching language of the Enneagram effortlessly fulfils both conditions.
Without the reader, the text would be empty: confirmation bias completes the illusion.
The Barnum effect alone generates agreement. This is transformed into a firm conviction by confirmation bias. Once someone sees themselves as a Type 2, they will henceforth tend to collect those memories and everyday scenes that fit the image of the caring helper, whilst overlooking the counterexamples. Over the course of weeks, a vague description thus becomes a perceived truth that is reinforced daily.
Added to this is the reader’s active role in interpretation. The Enneagram provides the framework; the individual fills it with their own life story. A sentence about ‘the need for authenticity’ becomes, for one person, a memory of a courageous decision to resign, and for another, a lament about an unsuitable relationship. The text remains the same; the perceived fit arises in the mind. The accuracy attributed to the model is one’s own achievement, which one merely lends to it.
Empirically, the Enneagram does not stand up to standard tests
A personality model must clear two hurdles. Reliability means that a test yields stable results when administered repeatedly. Validity means that it actually measures what it purports to measure, and that the postulated categories are reflected in the data. In the case of the Enneagram, the research evidence is sparse and sobering.
A systematic review published in 2020 examined the available research across numerous samples. Its conclusion is mixed to sceptical. Factor analysis studies consistently found fewer than nine independent dimensions, and no study was able to reconstruct the nine types from the data using cluster analysis methods. In other words: if you break down the responses statistically, the nine distinct types do not emerge. They are an arbitrary classification.
A personality researcher summarises the verdict in Inverse magazine by stating that the Enneagram is ‘pseudoscientific at best’. What this means is that the hallmarks of scientific measurement are missing: verifiable predictions, empirically derived categories and the fundamental possibility that the model could be discredited by reality. This is not to say that no one recognises any truth in it. Immunity to any refutation is one of the classic hallmarks of pseudoscience.
Even the scientific benchmark is less solid than one might think.
In discussions about the Enneagram, the Five-Factor Model – the Big Five – is often cited as a reputable counter-check. This model is indeed better substantiated, but it is only of limited use as a ‘gold standard’ against which everything can be measured. The Big Five are derived purely descriptively from statistical analysis of linguistic data; they are a by-product of factor analysis without any underlying theory as to why these five dimensions in particular should exist. They describe surface-level patterns; they do not explain anything.
Their claimed universal validity is also fragile. A large proportion of the underlying research stems from so-called WEIRD samples – from Western, educated, industrialised, rich and democratic societies. Where the model was tested outside this bubble, it fell apart. The 2013 study by Gurven and colleagues failed to replicate the five factors among the Tsimane, an indigenous community in the Bolivian Amazon. In 2019, Laajaj and colleagues confirmed, using data from 23 low-income countries, that the familiar five-factor structure cannot be clearly replicated there.
This does not exonerate the Enneagram; it shifts the perspective. Even the most reputable personality models should be interpreted with greater caution than self-help literature suggests. If even the best available framework is culturally limited and theoretically hollow, a system that derives its nine types from esoteric tradition should certainly be treated with even greater caution.
An industry has grown up around the Enneagram that thrives on interpretation.
The Enneagram has long since become a market. A wide-ranging industry has formed around the nine types: paid Enneagram tests online, certification courses, books, podcasts, team workshops and coaching programmes for professional personal development. Companies book seminars to categorise their workforce by type, and entire consultancy practices build their business on the promise of self-awareness through the Enneagram.
This commercial dynamic explains much of the system’s enduring popularity. A product that immediately provides everyone with a positive ‘aha’ moment sells exceptionally well, regardless of its empirical basis. The Barnum effect is the perfect business model: the product proves its worth in the customer’s experience because the customer does the crucial work themselves. Criticism of its validity rolls off this experience, because it simply feels right.
Problems arise when the entertaining self-test becomes a tool for control. When managers allocate tasks according to Enneagram types or job applicants are assessed based on their number, an unproven typology gains real power over people’s life paths. A model that does not stand up to scientific scrutiny should not underpin such decisions.
Why an entire culture resorts to ready-made pigeonholes
More interesting than the question of whether the Enneagram is accurate is the question of why so many people want to believe in it. The longing to be a particular type is a longing for relief. Anyone who knows they are a Four no longer has to endure the agonising openness of their own existence. The self is transformed from a task into a diagnosis, from something that must be painstakingly shaped into something that needs to be looked up. In an age of constant self-optimisation, this is an understandable desire.
From a psychoanalytical perspective, this categorisation serves a dual function. It creates identity by casting a diffuse sense of self into a definable form, and it alleviates the fear of one’s own contradictions. This leads to an impoverishment. Anyone who identifies with a number confuses a snapshot with their true nature and begins to adapt their behaviour to fit the label. ‘I was classified as Type 1 in the test’ becomes ‘That is just the way I am’, and the pigeonhole that began as an explanation becomes a shackle.
Self-knowledge worthy of the name works differently. It withstands the tension inherent in the fact that a person is ambiguous, changeable and never fully described. The Enneagram offers the opposite: an immediate, flattering, definitive answer. This is precisely where its comfort lies, and this is precisely where its limitation lies. Anyone who wants to get to know themselves will eventually have to leave the nine doors behind.
The essentials in brief
• The Enneagram classifies people into nine personality types, each with a core motivation and a fundamental fear, supplemented by wings and the arrows of integration and disintegration.
• Its origins are esoteric: the symbol comes from Gurdjieff, whilst the psychological interpretation is by Oscar Ichazo and Claudio Naranjo. The nine types were established; they were not derived from data.
• The perceived accuracy is generated by the Barnum or Forer effect (Forer 1948): vague, general human statements in which almost everyone recognises themselves. The confirmation bias reinforces this belief.
• Empirically, it lacks reliability and validity. Factor analyses identify fewer than nine dimensions, whilst cluster analyses fail to reconstruct the nine types. Experts describe the model as pseudoscientific.
• Even the commonly used benchmark, the Big Five, is theoretically empty and culturally limited (WEIRD samples; Gurven et al. 2013; Laajaj et al. 2019), and is therefore of only limited use as a gold standard.
• A coaching industry has grown up around the Enneagram, whose business is based on the immediate ‘aha’ moment. As a tool for guidance in the workplace and in recruitment, an untested type model is dangerous.
• The real question is a cultural one: the longing for a ‘type’ is a longing for relief from the openness of one’s own self.
Sources
• Forer, B. R. (1949). The fallacy of personal validation: A classroom demonstration of gullibility. Journal of Abnormal and Social Psychology, 44(1), 118–123. Summary: Barnum effect (Wikipedia); Bertram Forer (Wikipedia)
• Hook, J. N. et al. (2021). The Enneagram: A systematic review of the literature and directions for future research. Journal of Clinical Psychology. PubMed 33332604
• Anthes, E. (2021). Enneagram personality test: Why experts say it is ‘pseudoscientific at best’. Inverse. inverse.com
• Whitaker, K.: What’s Wrong with the Enneagram. Useful Tool or Pseudoscientific Fad? Medium
• On its origins: A Short and Comprehensive History of the Enneagram’s Origins (Gurdjieff, Ichazo, Naranjo). integrative9.com
• Gurven, M. et al. (2013). How universal is the Big Five? Testing the five-factor model of personality variation among forager-farmers in the Bolivian Amazon (Tsimane). Journal of Personality and Social Psychology. PubMed 23245291
• Laajaj, R. et al. (2019). Challenges to capturing the Big Five personality traits in non-WEIRD populations. Science Advances, 5(7). science.org
• On the Forer effect and its replication: EBSCO Research Starters, Barnum effect. ebsco.com
Related: