psychopy.org | Reference | Downloads | Github

Negative Reaction Times

OS (e.g. Win10): MacOS 10.13.6
PsychoPy version (e.g. 1.84.x): 3.1.2
Standard Standalone? (y/n) If not then what?: yes
What are you trying to achieve?:
I am looking to understand why I am getting negative reaction times in my output files.

Hello!

I am trying to make a learning task where participants must indicate the location of a filled in square with a corresponding button press. Specifically, participants see four empty squares in the center of the screen, when one of the squares is shaded black, the participant must indicate which square is shaded black with a corresponding button press on a keyboard. The goal for the participant is to learn the sequence in which the squares are shaded back.

However, for some trials, I am getting negative reaction times. It seems like when a participant learns the sequence and is able to anticipate the timing of a shaded square, the issue emerges. This means, if a participant learns the sequence and can make a response right as the stimuli appears (within 200 ms of trial onset), negative reaction times sometimes occur. The negative reaction times are typically between 1 and 50 ms, so I am also not sure if this is occurring because a response is made between trials (or after image_4 disappears and before image_5 appears). I have tried shortening the response time such that a response cannot be made until .05 seconds after trial onset, but the issue still occurred.

I am using version 3.1.2 (MacOS 10.13.6) as a previous thread suggested this version fixed this type of issue, however I am still finding it. BUT, I am not sure if it is because I have set up the routine incorrectly, which is what I suspect.


Image_5 displays a picture of a shaded in square.
Image_4 displays a picture with all empty squares.
code has some script for the outputfile. The only line regarding reaction time is as follows:
if not key_resp_7.keys : #if no response
outfile.write(“0”)
else:
outfile.write(str(key_resp_7.rt*1000))
outfile.write("\n")
Key_resp_7 is set to store the first key response, if that is of use.

Any help is appreciated!

Hi @ted, would you mind sharing the task so I can take a look at the response timing issue?

@dvbridges, Thanks for the response. The file is below.

Sequence.psyexp (50.2 KB)

Would you be able to send me the whole task, with stim included, as a zip folder? I cannot actually run the experiment without the stim and the conditions files. I just want to make sure I have the same set up as you in order to recreate the error.

Hello all, I was wondering if this issue had been resolved? I’ve just checked my output file after testing a participant and I also have a negative RT (-0.01s). Many thanks

@rachel.rodrigues, what version of PsychoPy are you using?

Hi David, it’s v 3.1.2