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Noticing latency is very context sensitive. A fun example is drawing lines on a touchscreen. Even ~20 milliseconds manifests as a visible gap between the tip of the pen and the line that "chases" it.

Temporal resolution of human hearing obviously varies with what exactly you measure but I believe it is in a single digit millisecond range for discerning between two clicks in quick succession and a single click.

Even 1ms.

While participants performed dragging and scribbling tasks, very low levels of latency could be discriminated, i.e., ~1 versus 2 milliseconds [...] [0]

[0]: https://www.semanticscholar.org/paper/In-the-blink-of-an-eye...

Reaction time is something entirely different from being able to notice latency. Read the article, it's addressed there.

You may be thinking of the same guy, he has his earlier article[0] linked from this one

[0] https://danluu.com/input-lag/