She had set up dozens of routers. When her grandfather asked for help getting online, the instructions came naturally: open a browser, type the router's IP address, log in with the admin credentials, navigate to the firmware update page, click Apply.
He stared at the screen. He did not know what a browser was. He did not know where to find an address bar. He did not know what admin credentials were or where to look for them.
She had assumed he knew these things because she used them without thinking. The gap between what she knew and what he knew had become invisible to her. The explanation was clear to her. To him, it was a series of unrecognisable steps.
What It Is
The curse of knowledge is a cognitive bias in which a person who is well-informed about a topic finds it extremely difficult to think about that topic from the perspective of someone who lacks that knowledge.
People who know a fact tend to overestimate the likelihood that others know it too. The better-informed person cannot easily un-know what they know. When they try to explain something, they start from their own mental model and insufficiently adjust for the explanatory steps that someone without that model would need.
The result is explanations that are accurate but incomplete - clear to the expert, confusing to the novice.
The Mechanism
The bias operates through egocentric anchoring: when trying to imagine what someone else understands, the starting point is your own understanding. The adjustment away from that starting point is systematically insufficient.
This is not carelessness or arrogance. The expert genuinely cannot retrieve the experience of not knowing. The foundational concepts feel so obvious that their role as prerequisites becomes invisible. Background knowledge that was once effortful has become automatic. What took years of practice now takes no conscious attention - and so the expert does not see it as something that needs to be taught.
The curse of knowledge leads to less effective explanations because the explainer omits necessary background information. The omission is not deliberate. It is produced by the inability to reconstruct what is non-obvious.
Where It Shows Up
Teaching and training. An expert teacher who has deeply internalised a subject will often confuse beginning students not by explaining incorrectly but by skipping the foundations that beginners need. The professor who assumes familiarity with basic notation or prerequisite concepts will lose students early and not understand why.
Technical documentation. Software developers, engineers, and technical writers routinely omit setup steps, assumption declarations, and basic definitions that are obvious to practitioners but essential to newcomers. The documentation passes expert review - everyone on the review team already knows what it assumes.
Medical communication. A clinician explaining a diagnosis or treatment plan using technical vocabulary may leave the patient less informed than they were before the conversation, not because the information was withheld but because the required background was not provided.
Product and interface design. Designers who are deeply familiar with their own product often create interfaces that seem intuitive to them and impenetrable to first-time users, because the design reflects the expert's model of the system rather than the new user's.
What It Is Not
The curse of knowledge is not the same as the false consensus effect, which is the tendency to assume others share your beliefs, opinions, or preferences. The curse of knowledge is more specific: it concerns the overestimation of others' factual knowledge and the inability to reconstruct a novice's perspective. Both involve anchoring on the self, but the curse of knowledge is specifically about the gap between knowing and not knowing.
It is also not simply a matter of effort. Trying harder to be clear does not automatically eliminate the bias. The problem is that the explainer cannot identify which parts of the explanation are missing - the absent background is precisely the part that feels obvious.