Record responses in a time window following a target, but only accept the first as a hit

Coding
1

I’m having trouble with keyboard response for hits and false alarm.

Description of exp: In my exp, subjects need to respond whenever they see target word, and not when they see non target word. Targets/non targets are presented once per second, but I want to give subjects a couple of second chance to respond. However because the target is presented at random, another target will be presented in this time window sometime. If/when this happens, the time window should (of course) start again for this new target.

Description of problem: The problem I am having is I only wish to accept 1 response as a hit in the response window, and any others should be discarded or considered false alarms. I find that I can’t seem to make this work. I keep running into problem. Either I accept all key responses within this window, which leads to all being accepted as hits, or I only allow to accept one response, which prevents storing additional keys (false alarms or further hits if a new target falls into the same window).

Code:

target = visual.TextStim(win=win, name=‘text’, text=u’HATE’, font=u’Arial’, pos=(0, 0), height=0.1, wrapWidth=None, ori=0, color=u’white’, colorSpace=‘rgb’, opacity=1, depth=-2.0);

non_target = visual.TextStim(win=win, name=‘text’, text=u’HAIE’, font=u’Arial’, pos=(0, 0), height=0.1, >wrapWidth=None, ori=0, color=u’white’, colorSpace=‘rgb’, opacity=1, depth=-2.0);
trial_Clock = core.Clock()

time = 0
frameN = 0
continueRoutine = True
while continueRoutine:
time = trial_Clock.getTime()

if time < 60:
    win.flip()
    frameN = frameN + 1
    if frameN == 1:
        target_rng = random.randint(1,11)
    if frameN >= 42+18:
        frameN = 0       
    if frameN in range(42,42+19,18):
        if target_rng in range(1,3): #target
            target.draw()
        elif target_rng in range(3,11):
            non_target.draw()

if time >= 60.0 and trial_Clock >=60:
    continueRoutine = False
    win.flip()

Using the below, I try and make it so only one key response is accepted as a hit within the time window, and any other are taken as false alarm. No matter what I can’t seem to get it working

   theseKeys = event.getKeys(keyList=['enter'])
   if len(theseKeys) > 0: #this or just the last key
      if time in range (target_time[-1], (target_time[-1] + 3.5)):
           target_hit + 1
           false_alarm + (len(theseKeys) - 1)
           event.clearEvents(eventType='keyboard')

I concerned that this may not work due to how I have coded the presentation timing of stimuli (because they are presented based on framerate, which resets every 60 frames i.e. once per second)

2

Hi Hugo,

was the code in which you checked the keypresses within the trial loop? Then I think it could be problematic that you implemented the condition:

if len(theseKeys) > 0:

This becomes True anytime the ‘enter’-key is pressed. If you use this condition in the loop, the length can’t exceed 1, because you clear all events afterwards.

Maybe you need to restructure so that you check the time window first and then use if + else if to check for first, second, third… keypresses.

Don’t know if this helps and maybe I am wrong (no expert here) :slight_smile:

Cheers,
Carola