The body · 3/6
The era
It was this dimension that convinced me. Two studies, two populations with nothing in common, the same shape of result: the same person, measured twice, gives different numbers.
The same person, two days later
Two days apart changed the number. In both groups.
SharifMeasured Fitts’s law in the same 55 people on two different days, with and without fine motor limitation, and it came out statistically different in the two groups. His too is the count of what it costs to read a chart through a screen reader, and the test of which sounds work best for that reading.3 references in this work:2020The reliability of Fitts’s law as a movement model for people with and without limited fin…2021Understanding screen-reader users’ experiences with online data visualizations2022“What makes sonification user-friendly?”: exploring usability and user-friendliness of son…See in the bibliography → et al. (2020) measured pointing in 55 people, across two sessions less than two days apart. They compared one session with the other.
It came out statistically different. In the group with fine motor impairment and in the group without. Nothing had changed in anybody’s body. What changed was the day, the sleep, what happened before the person sat down.
The recommendation they close the paper with is to measure across more than one session, especially when evaluating assistive technology. It is a modest request and it hides a large thing: if two days move the number, the number is not the person’s, it is the person’s on that day.
The same person, before and after the harvest
The same farmers, tight and comfortable, gave different numbers on the same test. What changed was the bank balance.
ManiMeasured farmers in Tamil Nadu before and after the harvest. The same farmers did better on the tasks after being paid.One reference in this work:2013Poverty impedes cognitive functionSee in the bibliography →, Mullainathan, Shafir and Zhao (2013) followed sugar-cane farmers in Tamil Nadu, India. Cane is harvested once a year and paid in one lump — so the same farmer spends some months tight and some months comfortable, every year.
They ran cognitive tests at both moments. The same men did better after being paid. The authors put the set of effects they measured at around thirteen IQ points, and record in the same sentence that the field effect, the one from these farmers, is three quarters of the laboratory effect.
The same person, the same brain, the same schooling, the same birth month. What changed was the bank balance.
Keep that in mind the next time someone says the user “did not understand the form”. Maybe they understood it perfectly in March.
And the law has a date too
Fitts measured in 1954, and Miller’s seven became four.
Paul Paul Morris FittsMeasured, in 1954, the time to point at a target as a function of its distance and size. Young, right-handed, in a laboratory.One reference in this work:1954The information capacity of the human motor system in controlling the amplitude of movementSee on Wikipedia ↗See in the bibliography → measured in 1954, with right-handed young people, in a laboratory, tapping a stylus on metal plates. Miller’s lawGroup into blocks of up to four, and make the blocks contrast with each other.Open the law → came out in 1956 with the magical number seven, and the seven became four when someone measured again with a better method.
A constant of physics does not halve because the decade changed. These do. Not because science failed — because it worked, and the second measurement was better than the first.
What that asks of us is modest: cite the date along with the law. “George Armitage MillerWrote, in 1956, the magical number seven paper, which the field itself later corrected to about four.One reference in this work:1956The magical number seven, plus or minus twoSee on Wikipedia ↗See in the bibliography →, 1956” says more than “Miller’s Law”, and it says it for free.
The other five dimensions
Where this touches the catalog