In its earliest use in the 13th century, “personality” referred to the quality, character or fact of being human. By the 18th century, the word pointed to the traits that made a person a distinctive individual. The 19th and 20th centuries saw the rise of systems designed for the mass classification of human beings, including personality tests. Today, these tests are more beloved and far-reaching than ever, especially on websites like BuzzFeed and Facebook. These tools and typologies are based on powerful, enduring myths about what personality is and how we can measure it. Here are five.

Myth No. 1

Personality is innate.

To many practitioners of and believers in personality assessment, personality is forged in the “dreamlike chaos” of infancy, as Katharine Briggs, co-creator of the Myers-Briggs Type Indicator (MBTI), liked to say. “Every one of us is born either an extravert or an introvert, and remains extravert or introvert to the end of his days,” she claimed. Personality inventories like the MBTI or the Enneagram (which classifies people as one of nine personality types) claim that they allow their subjects to discover their “shoes-off selves,” as Briggs’s daughter, Isabel Briggs Myers, described the true, immutable and essential you. One of the first and only major studies of personality development concluded that a child’s genetic makeup had a stronger influence on his personality than did his upbringing.

Yet longitudinal studies have reached different conclusions about when personality becomes fixed: during one’s school years or upon one’s entry into the workforce; at 17 or 21 or 25 or 30. Many of the systems of personality classification we use today (the MBTI, the Big Five) are based on flawed experimental design. Their conclusions were derived by studying subjects — medical students, research scientists or Air Force officers — whose results were not at all generalizable.

More important, the idea of a fixed personality is defined by and through the systems we use to assess it. Each system has its own language, its own historically and ideologically inflected understanding of what traits are determinative: Is it extroversion and introversion? Is it agreeableness or openness to new experiences? Do we assess these through multiple-choice questionnaires, checklists of self-descriptive adjectives, ink blots, life records or one-on-one interviews? Do we categorize them dichotomously or plot them along a bell curve? Do we present them as a portrait of the whole person or a modest exercise in trait measurement? There is nothing innate or natural about the way we discuss personality; it is a human invention.

Myth No. 2

Personality tests are based on psychological science.

Personality tests are used by psychologists and counselors. They are taught in psychology, education and business courses, and featured in textbooks like “A Practical Guide to the Thematic Apperception Test” and “Essentials of Myers-Briggs Type Indicator Assessment.” The American Psychological Association calls facility with them a necessary “proficiency in professional psychology .”

But some of the most popular personality assessments were produced by amateurs and autodidacts. Briggs and Myers had no formal training in psychology or sociology. They were wives and mothers who believed that their daily domestic labors — managing their households, tending to the emotional needs of their children and husbands — made them especially suited to understanding individual personalities and interpersonal relations. They designed their system of types by poring over Carl Jung’s quasi-mystical opus “Psychological Types” (1921), biographies of famous men and 19th-century novels, and by deriving questions from their readings that they tested on their family members and friends around their kitchen tables.

They were not the only ones who looked to literary sources for inspiration. The Humm-Wadsworth Temperament Scale, a popular personality indicator from 1935 that sorted people into five different types, drew on the novels of Dostoyevsky and Flaubert. (The creators cited Raskolnikov’s bilious, irritable attitude and Emma Bovary’s mercurial moods.) Even Henry Murray, a director of the Harvard Psychological Clinic and co-inventor of the Thematic Apperception Test , attributed his understanding of narcissism to Herman Melville, “the greatest depth psychologist America ever produced.”

Myth No. 3

The questions on personality tests are free of prejudice.

Personality tests often purport to ask questions that are neutral or unthreatening. The MBTI’s questions, for instance, provide a “positive and neutral ground” from which to address work or relationship problems, promises Naomi Quenk, the author of “Essentials of Myers-Briggs Type Indicator Assessment.” At first glance, this seems true. Consider the following two questions: “In your daily work, do you (a) rather enjoy an emergency that makes you work against time; or (b) usually plan your work so you won’t need to work under pressure?” And: “In planning a trip, would you prefer to (a) most of the time do whatever you feel like that day; or (b) know ahead of time what you’ll be doing most days?”

The MBTI’s publishers say the questions are appropriate for anyone who can read at a seventh-grade level, but that leaves out a huge swath of the world’s population. And the questions are exclusionary in their content and framing. They involve making decisions about what to do at parties (talk to everyone or just one person), how to plan a vacation (ahead of time or at the last minute), or how to succeed at an office job or at school. The scenarios they depict are impenetrably bourgeois; many people have never had the money, the leisure time or the opportunity to make these kinds of decisions.

Myth No. 4

Personality assessments are valid and reliable.

Personality tests are sold on the promise that they are valid (they measure what they say they will measure) and reliable (they produce consistent results). “Many studies over the years have proven the validity of the MBTI instrument,” says the Myers & Briggs Foundation . “Based on results from a nationally representative sample of 1,378 people,” claims the MBTI’s publisher, CPP, the indicator’s “median internal consistency . . . is .77.” (The benchmark for reliability is 0.7.)

Yet every major personality test has faced challenges to its reliability and validity. Tests like the Minnesota Multiphasic Personality Inventory and Rorschach are prone to over-pathologizing subjects, misidentifying them as addicts or abusers. Studies outside of literate, urban populations have failed to find support for the Big Five, another taxonomy. A 1991 study commissioned by the National Research Council on the MBTI found that the indicator’s test-retest reliability — whether you got the same results when you took it more than once — fell woefully short of the APA’s reliability benchmarks: Only 24 to 61 percent of subjects received the same result when they took it multiple times.

Myth No. 5

Personality assessments are harmless fun, like astrology.

“The Myers-Briggs is useful for one thing: entertainment,” declares Vox. “The Myers-Briggs Personality Test Is Pretty Much Meaningless,” echoes Smithsonian magazine. “Goodbye to MBTI, the Fad That Won’t Die,” exclaims organizational psychologist Adam Grant.

But personality tests shouldn’t always be considered a fun and unserious exercise, a distraction. Unlike astrology, personality tests are used by powerful institutions to make decisions with far-reaching consequences. One in five Fortune 1000 companies uses some means of personality testing to screen job candidates, both to hire the right type of person and to eliminate unfavorable types.

Because of their widespread use by employers and HR departments, personality tests have colonized and commodified the individual psyche. They have been used to prop up the idea that, if only we could find the jobs best suited to our personalities — if only we could “love what we do” — then we could bind ourselves to our work freely and gladly. This is tremendously beneficial to employers. It helps launch a “double-barreled attack upon turnover,” as Myers once said, by persuading people to do their jobs without complaining, without agitating, without dreaming of a better, more equitable or more just workplace — or a world where the workplace is no longer integral to social organization.

Five myths is a weekly feature challenging everything you think you know. You can check out previous myths, read more from Outlook or follow our updates on Facebook and Twitter.