How to implement feedback per response?
For one condition of a simple reaction time experiment, I'd like to implement feedback per response. The participants are supposed to press the Space bar in one second intervals as accurately as possible. After every keypress, a sketchpad should show how many ms the response deviates from the desired second.
I started using "Your response time was [response_time] ms." on a sketchpad (although this is not the deviation from the one second interval). I noticed that the shown response time does not fit the actual response time. For example, when I wait 5 seconds to press the space bar, the feedback sometimes shows numbers like 365 ms. When I respond extremely fast, the feedback sometimes shows numbers like 2514 ms. Can someone explain to me what I am doing wrong or even better, how to implement feedback per response that shows the deviation from a one-second interval?