There is a name for this, and executives have been using it deliberately since at least 2005.
The waiter rule
William Swanson, then CEO of Raytheon, published a booklet called Swanson's Unwritten Rules of Management that included what became known as the waiter rule, the idea that how someone treats a waiter, an assistant, or anyone else who cannot advance their career tells you more about their character than how they treat their boss. It spread through executive circles because hiring managers kept confirming it independently. Ron Shaich, former CEO of Panera Bread, has talked about taking candidates to lunch and then asking his assistant afterward how they were treated.
Why it holds up
The theory behind it is straightforward. Behavior toward someone with no power to reward or punish you is behavior with the performance stripped out. It is a more honest sample than anything said in a room where being watched is the point.
Where to start
This does not require a grand gesture. It requires noticing the moments that do not feel like they count, the assistant booking your travel, the intern on your project, the vendor rep you will probably never deal with again, and treating them the same way you would treat someone whose opinion of you might matter to your next promotion.
The test is whether you are the same person when nobody is checking, not whether you can be gracious under observation.
Reading which of your own interactions would actually pass this test, versus which ones you have not thought to notice at all, is worth being honest with yourself about. What this gives you is the specific kind of moment worth paying attention to.
There is a specific way to make small, low-power interactions genuinely count without them feeling performative, and it is worth building as a habit rather than a one time correction.