How to get reaction time within a frame by frame loop?

Coding
1

Hello everyone, how you all doing?

I have a (perhaps) simple question but I cannot find a solution!
I am coding a task similar to Posner, and I need to control not only the presentation of stimuli ( cue and target for example) by frames but also time intervals between these stimuli. This precise control is for a EEG experiment.

I just know how to do it by using a loop (using FOR or WHILE) frame by frame. But that means that if I put functions like clock or a mouse.reset or mouse.getpressed it will reset every frame (I think that is obvious). And I need to reset the mouse in the beginning of a stimulus presentation and to get the time of a button press from that presentation, without resetting every frame.

Can anybody help me?

(Just an observation: a function “core.wait(number of frames)” would be amazing if anyone feels like coding ;))

Here is the code for an one trial example:

from __future__ import print_function
from psychopy import visual, core, event, monitors

meuMonitor = monitors.Monitor('testMonitor')

win = visual.Window(meuMonitor.getSizePix(), monitor=meuMonitor,units='deg',fullscr=True,color=(-1, -1, -1))

mouse = event.Mouse(visible=False, win=win)

fixpoint = visual.Circle(win, fillColor=(1, 1, 1), units='deg', radius=0.1, pos=(0, 0))

grat1 = visual.GratingStim(win, tex='sqr', units='deg', pos=(11.5, -3.5), size=5, 
	sf=(1/0.53,0), phase = 0.50, color=(1.0, 1.0, 1.0), contrast=1.0, opacity=1.0)

grat2 = visual.GratingStim(win, tex='sqr', units='deg', pos=(-11.5, -3.5), size=5, 
	sf=(1/0.59,0), phase = 1, color=(1.0, 1.0, 1.0), contrast=1.0, opacity=1.0)

CueR = visual.Rect(win, fillColor=(1,1,1),width=1, height=1, pos=(0, 1)) #cue to indicate right
CueL = visual.Polygon(win, edges=3, radius=0.5, fillColor=(1,1,1), pos=(0, 1)) #cue to indicate left


StimDict = {
	'1': grat1,
	'2': grat2,
	'3': CueL,
	'4': CueR
}

# start trial

frameN = 0
press= False
while frameN <=250 and not press:

#for frameN in range(250):

    if 5<=frameN<250:#present fixation point for all frames
        fixpoint.draw()


    if 50<=frameN<100:   #present cue for a different subset
        mouse.clickReset()
        StimDict['4'].draw()
        button = mouse.getPressed()
        if button != [0, 0, 0]:
        	press = True   # finish trial


    if 150<=frameN<200:  #present target for a different subset
        mouse.clickReset()
        StimDict['1'].draw()
        button,tresp = mouse.getPressed(getTime = True)
        if button != [0, 0, 0]:
        	press = True
        	print(tresp) #only gets time from current frame!!!
   
    win.flip()#flip the screen every frame
    frameN+=1


win.close()

Thank you!!

2

Please enclose all of your code in triple backticks to make it more readable.

And also describe exactly what you want to achieve: you’ve only described the problem in generalities.

3

That’s a great idea!

As for your question: Shouldn’t it be possible to move the mouse.clickReset() call outside your loop so the timing doesn’t get reset each frame?

4

Hi Michael,
thanks for the tip about the code, didn’t know about the backtick.

Sorry I wasn’t specific about my problem…
I would like to get the reaction time from a response (mouse press) counting from the presentation of a stimulus.
For example, in my code a stimulus (grat1) is presented from the 150th to 200th frame (around 833 msec in a 60Hz refresh rate). I want to be able to get the time a mouse button is pressed counting from the first frame this stimulus was presented (150th frame).
For this I think I would need to reset the mouse from the beginning of the stimulus presentation and let the time count continuously until a button is pressed.
The idea of the coding is to know, for example, how long it took for a person to respond to a grating stimulus presented in the left side of the screen.

Is that more clear? Does that make sense?

@jan.freyberg Thanks for your suggestion! But putting the mouse.clickReset() outside the loop would only get the reaction time from the beginning of the trial, and I would like to get the reaction time from each stimuli presentation or from a specific stimulus.

Cheers!

5

In your case you can simply add a conditional to test for something that will only happen once (i.e. exactly on frame 150).

e.g.

if frameN == 150:
    mouse.clickReset()

In your case, your conditionals are tested serially so this doesn’t interfere with the other conditional statements, such as if 150<=frameN<200:.

6

Yeah! It works perfectly!
:grin:
Thank you!