They question everything and are skeptical of authorities.
They tend to ponder and melancholy.
They doubt themselves secretly or openly a lot.
They are not only very critical of others, but also very self-critical and downplay their own abilities.
They sometimes seem arrogant or rude without wanting or noticing.
When they are busy with something, they hate being disturbed or interrupted.
They are curious, eager to know and versatile.
They ask smart questions, but they often can’t give simple answers.
They talk more about issues than they do about people.
They often talk little, but when a favorite topic comes up, their eyes start to glow and they almost can’t stop talking.
They pursue unusual goals and projects.
You have an eye for details.
They have a penchant for perfectionism, but also for chaos and dispersal.
Some of them have a low tolerance for frustration.
They feel and experience intensely so intense that it sometimes overwhelms them and makes them feel empty.
They are usually eccentric, but can often hide it well, at least temporarily.
They have something childlike.
They have a sense of humour that is sometimes silly and sometimes oblique or strange.
They appreciate original ideas.
They don’t like squeaky-down phrases.
Their brains are very active and they think faster than they can write.
They are very sensitive and sensitive.
They hate injustice and have very strong feelings about it.
Because they endure injustice badly, they are often socially engaged.
They have different values from mainstream culture.
They are idealistic.
They are basically very honest.
They are often very tolerant of other people with idiosyncrasies that mainstream society does not accept.
They are usually either not believers at all, have an eclectic or idiosyncratic faith, or a very personal interpretation of a traditional religion.
They are individualists and fit poorly in groups, so they are often lonely (or feel lonely) and have few good friends.
You have difficulties with traditional career options.
They find themselves in traditional gender roles.
They are often very attractive, but sometimes neglect their appearance.
They often feel bored or underwhelmed, especially when they cannot pursue their interests.
They often did not learn to make an effort because they did not have to do so in their childhood.
(Partially adapted from: Signs of Giftedness in Adulthood)
(Many of these peculiarities are reminiscent of ADHD and autism.Overlaps are very common. What Genius and Autism Have in Common | TIME.com)
(Another very readable article: Why intelligent people suffer more mental disorders | Big Think)