The short answer
The curse of knowledge is a cognitive bias that does more damage to design communication than any skills gap. It describes a simple failure: once you know something, you cannot easily imagine not knowing it. You assume the people you are communicating with share the context you have, because that context feels obvious to you. It is not obvious to them, it is just familiar to you. This is why design rationale so often goes unrecorded: the reasoning behind a decision feels self-evident to the person who made it, so it never feels worth writing down.
Why the reasoning never gets written down
There is a cognitive bias that does more damage to design communication than any gap in skill or diligence. It is called the curse of knowledge, and once you understand it, you start to see it everywhere in how design teams work, as well as how they fail to work.
The curse of knowledge describes a specific cognitive failure: once you know something, you cannot easily imagine not knowing it. The knowledge feels like a natural part of how you see the situation, not like a specific piece of information you acquired. So when you communicate, you unconsciously assume the people you are talking to share the context you have. They usually do not. The context is not obvious to others, it is just familiar to you.
This is the mechanism that explains why design rationale so often goes unrecorded. The reasoning behind a decision feels self-evident to the person who made it.
“Of course the summary page was removed, the testing was clear.”
“Of course the questions are in that order, the cognitive flow depends on it.”
From inside the designer’s own head, the reasoning does not feel like information. It feels like common sense. And common sense does not seem worth writing down.
The bias runs in both directions
The curse of knowledge does not just affect how practitioners record their own reasoning. It also shapes how they read other people’s work, and how others read theirs.
Look back at something you made a year ago and you will often find decisions that make you wonder what you were thinking. The reasoning that was self-evident at the time is now invisible to you, because you no longer have the context you had then. You have become a stranger to your own past reasoning.
The same thing happens, more strongly, when you look at a colleague’s work. The questions that come naturally — ‘why did they not just do it this way?’, ‘why did they not follow best practice?’ — are asked through your current lens of knowledge, not the lens the original decision was made through. They are mostly irrelevant questions, because they assume the original designer had the context you have now and chose to ignore it. Usually, they had different context, which led them to a reasonable decision that looks wrong only from where you are standing.
This is worth internalising because it produces humility in both directions. The reasoning that is obvious to you is invisible to others. And the reasoning that seems absent in someone else’s work was probably obvious to them at the time, and simply never recorded.
Why you cannot fix this with effort
The curse of knowledge is not a character flaw, and it cannot be eliminated through trying harder. You cannot simply decide to remember what it was like not to know something. The knowledge is already there, and it shapes your perception whether you want it to or not. Telling a designer to ‘communicate more clearly’ or ‘document more thoroughly’ does not address the bias, because the bias operates below the level of conscious effort. The designer genuinely cannot see the gap, because the gap is invisible from inside their own knowledge.
What you can do is build a habit that compensates for the bias without requiring you to overcome it.
The habit is this: assume the gap exists, every time, by default.
Assume that the reasoning obvious to you is invisible to everyone else. Assume that the colleague reviewing your work does not have the context you have. Assume that the version of you who returns to this work in a year will not remember why you made the choices you made.
The working belief that produces good documentation
Good documentation does not come from better writing or more thorough notes. It comes from a working belief: that nothing is obvious, and the reasoning has to be made explicit because no one else can see it.
This belief is what closes the gap that the curse of knowledge opens. A designer who assumes their reasoning is visible will record only the things that feel like information, such as the unusual decisions, or the contested calls. They will skip the things that feel like common sense, which are often the most important to record precisely because they are load-bearing and invisible. A designer who assumes their reasoning is invisible will record the things that feel too obvious to write down. Those are usually the things a future reader most needs.
The practical instruction that follows is counterintuitive: write down the thing you think is too obvious to record. The decision that feels self-evident is the one most likely to be reversed by someone who doesn’t share your context, precisely because you didn’t think it was worth explaining.
Instead of asking whether your reasoning is clear, assume it is not, and write down the thing you think is too obvious to record.
Frequently asked questions
What is the curse of knowledge in design?
The curse of knowledge is a cognitive bias where, once you know something, you cannot easily imagine not knowing it. In design, it causes practitioners to assume their reasoning is obvious to others, so they don’t record it. The reasoning feels like common sense rather than information. This is a primary reason design rationale goes undocumented — not because designers are careless, but because the bias makes their own reasoning invisible to them as something worth recording.
Why don’t designers document their reasoning?
Designers often don’t document their reasoning because of the curse of knowledge — the bias that makes their own reasoning feel self-evident rather than like information worth recording. From inside their own head, the reasoning feels like common sense. The decisions that feel too obvious to write down are frequently the most important to record, because they are load-bearing and invisible to anyone who doesn’t share the designer’s context. The bias operates below conscious effort, so it can’t be fixed by simply trying harder.
How do you overcome the curse of knowledge in a design team?
You cannot eliminate the curse of knowledge through effort, because it operates below conscious awareness. What works is building a habit that compensates for it: assume by default that your reasoning is invisible to others, that colleagues don’t share your context, and that your future self won’t remember why you made a decision. This working belief — that nothing is obvious — produces good documentation, because it prompts you to record the reasoning that feels too obvious to write down.
Why do other people’s design decisions often look wrong?
Other people’s design decisions often look wrong because you evaluate them through your current context, not the context in which they were made. The curse of knowledge means you assume the original designer had the information you have now and ignored it. Usually they had different information that led to a reasonable decision. The questions that come naturally — ‘why didn’t they just do it this way?’ — are mostly irrelevant, because they’re asked from a different vantage point than the one the decision was made from.