In a corridor, that half-second is what an observer sees.

Nobody counts your steps.

They see the start.

What we built was a cue.

I would rest two fingers on the inside of her forearm and press once, and she would initiate on that press, and the press came a beat before she would otherwise have gone.

Practiced enough, a person stops needing to think about it.

It is the same principle as a metronome and it is used in gait training for Parkinson’s patients every day of the week.

The second was the transfer — sitting to standing and standing to sitting, which are the two moments that give everything away.