Simultaneous response collection in Dual Task - python-3.x

Question

I'm trying to implement a dual task. Both task ask to judge a number. The stimuli appear shortly after one another with a variable interval (a_soa).
I need to collect the reaction times to the stimuli which are given on the keyboard (first task: y or x key; second task: , or . key). I'm currently struggeling to implement this because for the first task the program needs to start waiting for a response before the second task is even drawn. Then the second stimulus appears and marks the beginning of a possible response to the second task.
The code for both functions that I'm using and the main function are included below.
def StimPresent(a_soa, b_s1, c_s2):
"""
Function StimPresent(a, b, c) presents stimulus_1 (b) for SOA ((a) number of frames),
then it adds stimulus_2 (d) and shows both for max 60 frames
and returns time of stimulus onset (tim)
"""
if event.getKeys(keyList='escape'):
myWin.close()
core.quit()
for frameN in range(a_soa):
b_s1.draw()
fixation.draw()
if frameN == 0: # RT S1 starting immediately after flip
onsetS1 = RT1.getTime()
myWin.flip()
for frameN in range(a_soa, (a_soa+60)):
b_s1.draw()
fixation.draw()
c_s2.draw()
if frameN == (a_soa+1):
onsetS2 = RT2.getTime() #RT S2 starting immediately after soa flip
myWin.flip()
for frameN in range((a_soa+60), 300):
fixation.draw()
myWin.flip()
return [b_s1, onsetS1, c_s2, onsetS2, a_soa]
def GetRTs(onS1, onS2):
allkeys = []
event.clearEvents()
while len(allkeys)!=2:
if event.getKeys(['y']):
buttonR1 = 55
allkeys.append(buttonR1)
buttonR1Time = RT1.getTime()
theRT1 = buttonR1Time - onS1
elif event.getKeys(['x']):
buttonR1 = 44
allkeys.append(buttonR1)
buttonR1Time = RT1.getTime()
theRT1 = buttonR1Time - onS1
else:
buttonR1 = 666
allkeys.append(buttonR1)
buttonR1Time = 'NaN'
theRT1 = 'NaN'
if event.getKeys(','):
buttonR2 = 44
allkeys.append(buttonR1)
buttonR2Time = RT2.getTime()
theRT2 = buttonR2Time - onS2
elif event.getKeys('.'):
buttonR2 = 55
allkeys.append(buttonR1)
buttonR2Time = RT2.getTime()
theRT2 = buttonR2Time - onS2
else:
buttonR2 = 666
allkeys.append(buttonR1)
buttonR2Time = 'NaN'
theRT2 = 'NaN'
if RT2.getTime() - onS2 > 210:
break
elif event.getKeys(['escape']):
myWin.close()
core.quit()
return [buttonR1, buttonR1Time, buttonR2, buttonR2Time, theRT1, theRT2]
main program
for b in range(block < 2):
for thisTrial in trials:
"""
---------------------
Start des Durchgangs
---------------------
"""
RSIFix()
showChar = StimPresent(thisTrial.SOA, thisTrial.Stimulus_1, thisTrial.Stimulus_2)
s1 = showChar[0]
s1onset = showChar[1]
s2 = showChar[2]
s2onset = showChar[3]
soa = showChar[4]
responses = GetRTs(s1onset, s2onset)
Thanks for any help :)

Answer 1

If using the Psychopy's event module to collect responses, you need to integrate the checking for keypresses into your drawing loop. i.e. check for a keypress once for every win.flip() call, so that you are effectively checking for responses once per screen refresh (and effectively getting a very granular time resolution, typically at 16.67 ms for a 60 Hz display).
The way the event.getKeys() function works is that the timestamp is the time at which the function is called, not the time at which the key was pressed. i.e. in your current code, the key could have been pressed during the stimuli and be just sitting in a buffer waiting for you to process it. So all of your reaction times will appear to be after the stimuli have finished being shown.
Having said that, best practice now (from PsychoPy 3.1 onwards) is not to use the event module if reaction times are important. Instead, use the new Keyboard class:
https://www.psychopy.org/api/hardware/keyboard.html
This was ported from the Psychtoolbox project and has far better timing performance. And importantly, the timestamp reflects the actual time the key was pressed, regardless of when you check for responses, and doesn't have its resolution tied to the display refresh rate.

Answer 2

Thanks a lot, your comment helped me! I rewrote the code with the keyboard class but now I'm running into another problem: The function is only returning 666 as buttonR1Code and buttonR2Code. These should only be given if now response was collected.
How can I fix this? Any suggestions?
def StimPresent(a_soa, b_s1, c_s2):
"""
Function StimPresent(a, b, c) presents stimulus_1 (b) for SOA ((a) number of frames),
then it adds stimulus_2 (d) and shows both for max 60 frames
and returns time of stimulus onset (tim)
"""
kbR1 = keyboard.Keyboard()
kbR2 = keyboard.Keyboard()
allkeys = 0
while allkeys < 2:
if event.getKeys(keyList='escape'):
myWin.close()
core.quit()
for frameN in range(a_soa):
b_s1.draw()
fixation.draw()
if frameN == 0: # RT S1 starting immediately after flip
onsetS1 = RT1.getTime()
kbR1.clock.reset()
keyR1 = kbR1.getKeys(['y', 'x'], waitRelease=True)
if keyR1 == 'y':
buttonR1 = 55
allkeys += 1
buttonR1Iden = keyR1.name
buttonR1Dur = keyR1.duration
theRT1 = keyR1.rt
elif keyR1 == 'x':
buttonR1 = 44
allkeys += 1
buttonR1Iden = keyR1.name
buttonR1Dur = keyR1.duration
theRT1 = keyR1.rt
myWin.flip()
for frameN in range(a_soa, (a_soa+60)):
b_s1.draw()
fixation.draw()
c_s2.draw()
if frameN == (a_soa+1):
onsetS2 = RT2.getTime() #RT S2 starting immediately after soa flip
kbR2.clock.reset()
keyR1 = kbR1.getKeys(['y', 'x'], waitRelease=True)
keyR2 = kbR2.getKeys(['.', ','], waitRelease=True)
if allkeys == 0:
if keyR1 == 'y':
buttonR1 = 55
allkeys += 1
buttonR1Iden = keyR1.name
buttonR1Dur = keyR1.duration
theRT1 = keyR1.rt
elif keyR1 == 'x':
buttonR1 = 44
allkeys += 1
buttonR1Iden = keyR1.name
buttonR1Dur = keyR1.duration
theRT1 = keyR1.rt
if allkeys == 1:
if kbR2.getKeys(keyList=['.'], waitRelease=True):
buttonR2 = 55
allkeys += 1
buttonR2Iden = kbR2.name
buttonR2Dur = kbR2.duration
theRT2 = kbR2.rt
elif kbR2.getKeys(keyList=[','], waitRelease=True):
buttonR2 = 44
allkeys += 1
buttonR2Iden = kbR2.name
buttonR2Dur = kbR2.duration
theRT2 = kbR2.rt
myWin.flip()
for frameN in range((a_soa+60), 300):
fixation.draw()
deadlineS1 = 210
deadlineS2 = 210
keyR1 = kbR1.getKeys(['y', 'x'], waitRelease=True)
keyR2 = kbR2.getKeys(['.', ','], waitRelease=True)
if allkeys == 0:
if keyR1 == 'y':
buttonR1 = 55
allkeys += 1
buttonR1Iden = keyR1.name
buttonR1Dur = keyR1.duration
theRT1 = keyR1.rt
elif keyR1 == 'x':
buttonR1 = 44
allkeys += 1
buttonR1Iden = keyR1.name
buttonR1Dur = keyR1.duration
theRT1 = keyR1.rt
elif frameN > deadlineS1:
buttonR1 = 666
allkeys += 1
buttonR1Iden = 'NaN'
buttonR1Dur = 'NaN'
theRT1 = 'NaN'
if allkeys == 1:
if kbR2.getKeys(keyList=['.'], waitRelease=True):
buttonR2 = 55
allkeys += 1
buttonR2Iden = kbR2.name
buttonR2Dur = kbR2.duration
theRT2 = kbR2.rt
elif kbR2.getKeys(keyList=[','], waitRelease=True):
buttonR2 = 44
allkeys += 1
buttonR2Iden = kbR2.name
buttonR2Dur = kbR2.duration
theRT2 = kbR2.rt
elif frameN > deadlineS2:
buttonR2 = 666
allkeys += 1
buttonR2Iden = 'NaN'
buttonR2Dur = 'NaN'
theRT2 = 'NaN'
myWin.flip()
return [b_s1, onsetS1, buttonR1, buttonR1Iden, buttonR1Dur, theRT1, c_s2, onsetS2, buttonR1, buttonR1Iden, buttonR1Dur, theRT2, a_soa]
Thanks :)