A new image cannot become visible until it is presented and scanned out to the display. More refresh opportunities can reduce the waiting time between a rendered update and a visible update.
The exact latency depends on when the frame becomes ready relative to the refresh cycle and how the monitor scans and processes it.
A 240 Hz monitor can still have processing or pixel-response behaviour that contributes to latency. Likewise, a game may not deliver enough frames consistently to make full use of the display.
Mouse/input latency and human reaction remain separate components.
A 2024 experimental preprint comparing 30, 60, 120, 144 and 240 Hz in an FPS task found a clear performance penalty at 30 Hz, while differences among the higher refresh conditions were less decisive in that sample.
That is consistent with diminishing practical gains: higher rates can improve temporal resolution, but performance does not scale linearly with the Hz number.
Use the same monitor and system, change only the refresh setting, verify the operating system actually applied it, and run many trials. Compare the full distribution because normal human variability can be larger than the nominal frame-time difference between two high-refresh settings.
It refreshes 2.4 times as often, but that does not make a person react 2.4 times faster.
It has a shorter frame interval, but the practical benefit depends on the system, application, monitor and user.
It can reduce the display-side wait for visual updates. It does not remove mouse, system or panel-processing latency.