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Looking Time Keyword

<LookingTime [modifiers] N,text>
<lt [modifiers] N,

    Parameter and switch to turn on the Looking Time features of DMDX, loads counter N with the time key text was pressed during each trial.   modifiers are optional modifiers to the way the key presses are summed of which there is only one, LONGESTLOOKINGTIME currently.  If N is -1 then the RT for that trial is set instead of a counter.   This is a special extension of the <Zillion> input mode that sums the time a key was pressed while the clock was on, multiple counters and keys can be bound per trial.  If LONGESTLOOKINGTIME is used the time will be the longest single time the key was pressed.   The name text can either be +buttonname or -buttonname, (see Input).  Prior to version either would do as both names were used to determine if a key is pressed, however now if the released version of the button name is used (-buttonname) then the counter or RT will be assigned the looking away time, ie how long the key wasn't pressed for.   Counters do not have to be initialized with <SetCounter> before hand (they couldn't be on the parameter line in any event) and can be stored in the data file with <EmitCounter>.
    A little care is needed if
<Emit> is to be used as <Emit> emits the counter's value as the item is parsed, before any RTs are gathered so a <Call> is necessitated.   The following example monitors two looking times, one with the 1 key and the other with the 2 key, it also sets the RT to the first looking time:

<ep> f70 <id keyboard> <zil> t20000
<lt -1,+1> <lt 1,+1> <lt 2,+2> <eop>

0 "This is the Looking Time Test Item file" <bu 999>;
10 <emit 1><emit 2><return>;
~999 <medialife 999>
<dv> "movie.mpg" ;

+1 "+" / * <dv> "movie.mpg" <call -10> c;
+2 "+" / * <dv> "movie.mpg" <call -10> c;

    Also, if <ValidateZillionKey> is used you will have to validate both the button press (+keyname) and it's release (-keyname) for <LookingTime> to work.

    As of version looking times can extend across items with the use of <ContinueClockOn> in the following items.  Key press data from earlier items in the raw dump will be negative relative the most recent clock on and the same key press data will appear in all items in the <cco> series (each being more negative than the last as it recedes in time).  Also use of the <AbortItemExpression> also requires special attention when combined with <lt> and <cco>,  where you must retest the abort item expression before trials with a <cco> in them and branch over the remaining <cco> items as they will all play a few frames of video before aborting themselves as the key press data that caused the original item to abort will still be present when <cco> restores it...

<fd 60>
<safemode 1>

<zil> <id keyboard> <lt longestlookingtime 4, +s> <aie c4 .gt. 2000>

<timeout 20000>
<cr> <nfb>
<bgc 0> <wc 255255255>

+1 <dv> "movie.mpg" *;
~1 <bi 2, c4 .gt. 2000>;
+1 <dv> "movie.mpg" <cco>;
~1 <bi 2, c4 .gt. 2000>;
+1 <dv> "movie.mpg" <cco>;
~2 ;


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