Motion that does none of those jobs is pure cost

What it is

Orienting, time in the action loop, and the frame budget are all scarce. Motion that neither points to a change, nor draws belonging, nor fills a real wait still spends all three. That motion is pure cost: attention, time and rendering go out, and no interface question comes back.

“Looks nice” is not a fourth job. If it does not change detection, spatial binding or duration, it is spending scarce resource on decoration.

Why it happens

The tax is levied on three ledgers at once. First, local motion is an attentional capture device; a decorative bounce steals orienting from the task object and plants a false transient. Second, any non-zero duration occupies the intent–act–next-act loop; people often will not tap until the motion settles, and if they do they still wait for the screen to stop. Third, interpolation, compositing, blur and shadows eat the frame budget even when the duration looks short.

The three can land together. A brand spring-scale on a splash both blocks entry, produces large-field optic flow, and contends with first-frame rendering on the main thread. There is no state change that needed to be seen (the app is already opening), no belonging to declare, and the wait is not something this motion can shorten — launch time is set by loading; the scale is a tax stacked on top.

Where it stops holding

• Branding, cutscenes and performative motion in a game can be the product’s purpose. That is content, not an interface function, and it needs its own budget rather than being smuggled in as “motion design.”
• On first use, a short spatial demonstration may temporarily do belonging work; the same clip on the tenth visit collapses back to pure cost.
• Pure cost is almost invisible in a demo recording, which plays once and does not measure the gap before the next action.

Applying it

• For each motion, write the question it answers: where did it change / where did it come from / which wait is it filling. If all three are empty, delete it or freeze it.
• Splash, empty-state illustration and button micro-springs are the usual hiding places; default them off and keep only what survives the three questions.
• Check: remove the motion. If change detection, belonging identification and wait estimates are no worse, while task time drops or jank falls, the original motion was a tax.

Related

• Same group: F7.01.1 Motion draws attention to where change happened · F7.01.2 Motion shows where an element came from and belongs · F7.01.3 Motion fills a wait and changes how long it feels
• Nearby: F7.10 Motion abuse · F7.12 Performance cost of motion · F7.09 Parallax and vestibular discomfort
• Search terms: pure cost · decorative motion · attentional capture