The phrase bad habits of very intelligent people promises gossip and usually delivers flattery, a list of quirks that quietly reassure the reader they are one of the clever ones. The more interesting version of the question is harder on everyone, including the smart. It asks whether high intelligence comes with characteristic ways of thinking badly, and here the research is genuinely useful, because it points to traps that intelligence does not prevent and in some cases actively sharpens. What follows is a careful reading of that work, not a verdict on anyone. The habits worth naming are the ones the evidence can actually speak to.
Believing you are the objective one
The first and best documented bad habit is a particular blind spot. Most people readily accept that human judgment is warped by bias in general, while insisting that their own judgment is the exception. Psychologists call this the bias blind spot, and the obvious hope is that clever, reflective people would suffer from it less. A study by Richard West, Russell Meserve and Keith Stanovich tested exactly that. Across two studies they found robust bias blind spots for a range of classic thinking errors, and, strikingly, that none of these blind spots were reduced by measures of cognitive ability, reflective thinking, or open-minded thinking, with some tendencies pointing slightly the other way.
Read carefully, that is a pointed finding. The mental horsepower that helps a person spot flaws in an argument does not help them spot the same flaws in themselves, and the confidence that comes with being right a lot of the time can make the blind spot worse rather than better. A person who is used to being the smartest in the room learns to trust their own conclusions, which is precisely the habit that stops them from auditing those conclusions. It is one study tradition rather than the whole of psychology, but the effect has held up well, and its lesson is uncomfortable for anyone who prides themselves on objectivity.
Using brainpower to defend the answer you already wanted
The second bad habit is subtler and, if anything, more troubling, because it turns intelligence into a tool for the wrong job. The optimistic view is that giving people better reasoning skills should help them read evidence more accurately. Sometimes it does. But when the evidence touches something a person cares about, skill can be turned to defending the preferred answer instead of finding the true one. Research on what is called motivated reasoning has examined how numeracy, the ability to reason with numbers, interacts with politically charged data. In this line of work, people higher in numeracy read a neutral set of numbers correctly, but when the same numbers were framed as a politically loaded result, the more numerate participants were more likely to twist the interpretation to fit their existing beliefs, not less.
This is the opposite of what a simple faith in intelligence would predict. The skill did not act as a brake on bias. It acted as an engine for it, giving the person a more sophisticated way to reach the conclusion they already favored and a more convincing case for why they were right to do so. The habit here is not stupidity but a misdirected cleverness, the quiet substitution of winning for understanding. It is worth adding that these are effects measured on average across groups, that some studies find the pattern is sensitive to how the task is set up, and that no single experiment settles it. But the direction is consistent enough to take seriously, and it undercuts the comfortable idea that smart people are natural truth seekers.
The habits that are folklore, and the grain of truth in them
Around these two well-supported patterns sits a cloud of popular claims that deserve more caution. Very intelligent people are said to overthink, to procrastinate through perfectionism, to grow bored easily, to struggle to finish what they start, and to be poor at explaining themselves to others. Some of these have threads of support in the research literature, and some are mostly stereotype dressed up as insight. The honest position is that the evidence for a tidy personality profile of the highly intelligent is thin, that the effects where they exist tend to be small, and that plenty of clever people show none of these traits at all. Treating them as a diagnostic checklist for genius is exactly the kind of loose reasoning the smart are supposed to avoid.
There is a real pattern underneath the folklore, though. A person who has been rewarded all their life for quick answers can come to lean on cleverness where patience, curiosity, or plain effort would serve better. The gift that opens doors early can crowd out the humbler habits that matter over a longer stretch, so that the very fluency which impresses in a meeting becomes a reason to stop listening. That is a tendency, not a rule, and it is a habit of a certain relationship to one’s own intelligence rather than a fixed feature of high ability.
Why this is worth knowing
None of this is an argument against intelligence, which remains one of the most reliable advantages a person can have, linked to better outcomes across health, work, and learning. The point is narrower and more practical. Intelligence is a tool, and like any tool it can be pointed in the wrong direction with great efficiency. The specific danger is that the same ability which lets a person reason well also lets them rationalize well, and rationalization feels identical to reasoning from the inside.
The corrective that the research implies is not less intelligence but more of a particular discipline: the deliberate practice of doubting your own conclusions, seeking out the strongest version of the other side, and treating your own certainty as the thing most in need of checking. That discipline is not measured by any intelligence test, which is rather the point. The worst habit of very intelligent people is assuming their intelligence has already done that work for them. It has not, and knowing that it has not is the beginning of thinking well.