KbWait ignoring keypresses

1

Hi All,


I am presenting stimuli and asking people to give a keyboard response. The problem I am having is that KbWait(-1,2) is ignoring key presses: it will consistently ignore the first press but then will consistently notice the second key press I make (i.e., I need to press a key twice to get KbWait to recognize it). Oddly, this does not happen for the numeric keys (1!, 2@, etc.), it only happens for the alpha-numeric ones. Any ideas on how to fix this would be greatly appreciated. Code to reproduce the problem is below:


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[window, windowRect] = Screen('OpenWindow', 0,[],[]);

Screen('TextFont',window, 'Times New Roman');

Screen('TextSize', window, 18);

HideCursor(window);

centeredspotRect = CenterRect([0 0 0 0], windowRect);

Priority(1);

Screen('Preference', 'SkipSyncTests',1);

Screen('Preference','VisualDebugLevel',0);

Screen('Preference', 'SuppressAllWarnings', 1);

%KbName('UnifyKeyNames');

ykey = KbName('Y');

nkey = KbName('N');

key1 = '1!';

key2 = '2@';

key3 = '3#';

key4 = '4$';

key5 = '5%';

key6 = '6^';

key7 = '7&';

RestrictKeysForKbCheck([ykey nkey key1 key2 key3 key4 key5 key6 key7]);

DisableKeysForKbCheck(13);

black = BlackIndex(0);



Screen('DrawText', window, '+', centeredspotRect(1)-.01*centeredspotRect(1), centeredspotRect(2)-.24*centeredspotRect(2), black);

Screen('flip',window)

WaitSecs(1)


Screen('DrawText', window, 'Please Get Ready.', centeredspotRect(1)-.09*centeredspotRect(1), centeredspotRect(2)-.24*centeredspotRect(2), black);

Screen('flip',window)

WaitSecs(1)


Screen('DrawText', window, 'Cats', centeredspotRect(1)-.18*centeredspotRect(1), centeredspotRect(2)-.24*centeredspotRect(2), black);

Screen('DrawText', window, 'Dogs', centeredspotRect(1)-.18*centeredspotRect(1), centeredspotRect(2)-.10*centeredspotRect(2), black);

Screen('DrawText', window, 'Demons', centeredspotRect(1)-.18*centeredspotRect(1), centeredspotRect(2)+.04*centeredspotRect(2), black);

Screen('DrawText', window, 'Yes(Y) or No(N)?', centeredspotRect(1)-.04*centeredspotRect(1), centeredspotRect(2)+.18*centeredspotRect(2), black);

RestrictKeysForKbCheck([ykey nkey]);

[~,FlipTime] = Screen('flip',window);

KbWait(-1,2)

[~,First_Answer] = KbWait(-1,2);

First_Answer = find(First_Answer);

First_Answer_Fluency = GetSecs - FlipTime;

sca

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Thank you in advance for your help.

-Michael