Week 2 Session: Three Thresholds

Week 2. The perception gap becomes engineering. Three numbers decide which affordance a delay is given.

22 February 2027

Last week you established that felt duration is its own quantity. This week it gets turned into engineering. Three numbers decide which affordance a delay is given, and once a delay is on the far side of one of them it is treated as a different kind of event.

Nielsen’s three limits are 0.1 seconds, 1 second and 10 seconds. Under the first, the system reads as instantaneous. Under the second, your train of thought survives the delay although you notice it. Past the third, you go and do something else. Miller got there twenty-five years earlier with terminals and a different vocabulary.

Read both and notice that neither is a measurement of a population. They are design limits, argued for. They have been copied into guidance for sixty years with the argument left behind.

In the workshop#

You audit one piece of software against the three limits. Find a delay, time it, and say which band it falls in and which affordance it was given. Then find one that was given the wrong affordance for its band, which will take about four minutes.

But wait, there’s more#

Open your operating system’s keyboard settings and find the key repeat delay slider. It is a control that lets you set a threshold for yourself. Almost every other threshold in this course was set for you by somebody you will never meet. Drag it to one end and try to type.