Put the same acute stroke case in front of ten physicians — the same age, the same deficit, the same imaging, the same clock — and you will not get ten copies of one decision. Somewhere between the numbers and the needle, the answers spread. Everyone who takes stroke calls has seen this happen in a room; almost no one has measured it on themselves.
Daniel Kahneman gave the spread its grammar. Bias is being wrong in the same direction every time. Noise is a group being wrong in different directions at once. Medicine has spent forty years auditing the first and almost none measuring the second.
The two hide in different places. Bias can be found from inside: audit your own decisions and the systematic lean eventually shows itself. Noise cannot — a single judge, examined alone, looks consistent. The scatter only appears when many judgements of the same case are laid side by side.
γνῶθι σεαυτόν — know thyself, the Delphic instruction — names the one measurement a clinician cannot take alone. You can know your own reasoning perfectly and still not know whether you are the outlier in the room. The only way to find out is to put the same case to everybody at once.
That is what this survey does. Constructed acute stroke cases, each sitting deliberately where the trials went quiet, are answered independently by physicians who make these decisions for a living. Laid side by side, the answers show each of us something no audit of our own files can: where we actually stand.
12 invented answers on the strip.
Nothing you add here is stored or sent.
Taking part
Who it is for. Physicians who make, or contribute to, acute stroke treatment decisions. No patients are involved and no patient data is collected — every case is constructed, written as fiction from the start.
What it asks. Six short cases, about ten minutes, answered once, on your own phone or computer. The survey runs on this site; nothing is sent anywhere else. This page itself collects nothing.
What follows the cases. After the six cases, nine short questions check one fact behind each decision; the answers, with their sources, appear when you finish.
Answered alone. Please answer without conferring — independent judgement is the measurement, and an answer agreed with a colleague measures the room instead of you.
Two groups, kept apart. Answers are gathered in two groups that are never pooled: physicians who heard the talk at Belstroke in Brussels on 16 September 2026, and physicians who arrive from this site or the feed. The conference route stays open for thirty days after the talk; the public route stays open.
What happens next. When a group reaches twenty respondents, its distribution appears on this page, one strip per case. Twenty is a publication rule, not a guarantee of anonymity or of representativeness. What is shown is variation in stated treatment inclination — never proof of bias, and never proof of clinical correctness. Respondents who leave an e-mail address receive a personal comparison against their group, sent by hand once the group is large enough; no date is promised.
I heard the talk at Belstroke Take part
Where the survey stands
Conference group: no answers yet. Public group: no answers yet. Counts updated 12 September 2026. Each group's distribution appears here when it crosses twenty.
Questions first: eurostrokes@gmail.com