如何使用心理工具箱在有限的时间内呈现刺激并仍然记录响应

Question

对于我的实验，我想向参与者提供一个刺激和一些说明。然后，2秒后，我希望刺激消失，但指令保留，直到参与者做出反应。参与者应该能够在刺激呈现后立即做出反应，并在刺激呈现后最多10秒做出反应。响应时间将被记录下来。

在我目前的代码中，参与者只有在2秒后(刺激消失后)才能做出反应。有没有办法让刺激只出现2秒，而指令仍然留在屏幕上，但参与者能够在刺激呈现后立即做出反应？

%Show the instructions and the stimulus   
           Screen('DrawTexture', window, randFaceTexture2);
           DrawFormattedText(window, [instructions1], 'center', 600)

           stimTime = Screen('Flip', window);

           WaitSecs(2);

           %Stimulus disappears but instructions remain 
           DrawFormattedText(window, [instructions1], 'center', 600)
           Screen('Flip', window);

           if GetSecs() <= stimTime + 10
           keyIsDown = 0;
           startTime = GetSecs();
                while 1
                     [keyIsDown, secs, keyCode] = KbCheck;
                     FlushEvents('keyDown');
                     if keyIsDown
                          nKeys = sum(keyCode);
                               if nKeys == 1
                                    if keyCode(yes) || keyCode(no)
                                         reactionTime = 1000*(GetSecs - startTime);
                                         response = KbName(keyCode);
                                         Screen('Flip', window);
                                         break;
                                    elseif keyCode(escKey)
                                         ShowCursor;
                                         fclose(outfile);
                                         Screen('CloseAll');
                                    return 
                                    end 
                                    keyIsDown = 0;
                                    keyCode = 0;
                               end 
                     end 
                end 
           else 
                line3 = 'Sorry you''re out of time';
                DrawFormattedText(window, line3, 'center', 'center');
                Screen('Flip', window);
                keyIsDown = 0;
                rt = 0;
           end

Answer 1

不使用WaitSecs()来控制刺激在屏幕上的时间量，而是在响应检查循环中关闭刺激，当适当的时间量过去时。下面的代码片段显示了对上述代码的相关更改。我省略了您如何轮询响应的细节。顺便说一句，我认为您使用'if GetSecs() <= stimTime + 10‘可能无法实现您想要的结果，在您的代码中，此语句将只计算一次，并且始终为真。

% time in seconds for the stimulus to remain onscreen
timeForStimulus = 2;
% time for the participant to respond, in seconds
timeToRespond = 10;

%Show the instructions and the stimulus
Screen('DrawTexture', window, randFaceTexture2);
DrawFormattedText(window, [instructions1], 'center', 600)

stimTime = Screen('Flip', window);
stimOnScreen = 1;

while GetSecs() <= (stimTime + timeToRespond)
    % turn the stimulus off, if the stim is on and the stim time has elapsed
    if (stimOnScreen == 1) && (GetSecs() > (stimTime + timeForStimulus))
        %Stimulus disappears but instructions remain
        DrawFormattedText(window, [instructions1], 'center', 600)
        Screen('Flip', window);
        stimOnScreen = 0;
    end

    % poll for keyboard response, etc.

end