The place

The Doherty ThresholdDoherty thresholdRespond in under 400 ms, even if only to say it is processing.Open the law → says that below 400 ms the machine answers you, and above it the machine makes you wait. It is one of the most cited numbers in interface design.

Walter DohertyDohertyMeasured, at IBM in 1982, the productivity gain when the computer responds in under 400 ms. It is the origin of the threshold that bears his name.One reference in this work:1982The economic value of rapid response timeSee in the bibliography → and Ahrvind Thadani measured it at IBM in 1982, with terminal operators. Trained people, seated, doing the same task all day, on equipment the company controlled end to end.

The number became a property of the human brain along the way. It is not a property of any brain. It is the measurement of one specific office, in one specific year, with a keyboard that no longer exists. On unstable 3G, on a five-year-old phone, 400 ms stops being a target and becomes fiction. What survives of the law is the principle, and the principle is excellent: always report the state. Just do not promise the number.

The cracked screen cuts the line of text. Brightness at minimum, so the battery lasts until they get home, changes the contrast you calculated. The data plan that runs out on the 20th changes what the person is willing to load. The hand holding the bus rail is not the hand Fitts’s LawFitts’s lawAn important target is a big target, close to where the hand already is.Open the law → measured.

None of that is in the user, it is around them, and it changes the result just the same.

LegibilityLaw of legibilityContrast, size and leading come before the choice of typeface.Open the law → is the most direct case: the contrast that passes on your calibrated screen, in an office with curtains, can disappear in two o’clock sunlight.

HenrichJoseph HenrichNicknamed WEIRD the group in which psychology is measured — Western, educated, industrialised, rich and democratic — and showed the size of the problem.One reference in this work:2010The weirdest people in the worldSee on Wikipedia ↗See in the bibliography → et al. (2010) nicknamed WEIRD the group in which almost all experimental psychology has been measured: Western, Educated, Industrialised, Rich and Democratic. The acronym also spells “weird”, and the joke is the argument.

Brazil is not that place. Neither is Vietnam, nor Nigeria, nor the outskirts of any of the capitals where the studies were run. When we cite a law here, we are importing a result together with an address — and the address does not come printed on the box.