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Inconsistent response times

OS : Windows 10
PsychoPy version: 3.2

Hi all,

I am trying to check the consistency of key press detection between .log file and .csv file using Builder.

To do so, I created a simple experiment (see picture) where I just display a letter using a Text component (to display the letters) and a Keyboard Component (to log key presses).

Then, when I run the experiment, I press a key every time a character is displayed with the intention of inspecting the ‘rt’ in the .csv file generated after the experiment is run.

I was expecting this ‘rt’ value in the .csv to be exactly the same as the response time computed from the -log file (Keypress time - autoDraw time), however this is not the case. There is always a difference between 1 to 8~9 ms, as you can check in the following image.

Sin título

I would like to know why these two values do not match.

Thanks,
Eduardo