Stop Signal Task

Hello,

I'm using the Stop Signal Task from the PsyToolkit experiments library. However, I'd like to adjust the code so I could use the tracking procedure for dynamic adjustment of the stop signal delay (Logan et al., 1997); I want to set the initial SSD to be 250 mls, and to adjust it after every "no go" trial - increase it by 50 mls if participants succeed inhibiting their response and decrease it by 50 mls if they fail to do so. After dozens of failed attempts (following a reading of the syntax guide, looking at examples and watching the fascinating videos) I would really appreciate an advice. This is my code at the moment:

# stop signal task

options
bitmapdir stimuli # the folder that contains the stimuli bitmaps
set &d 0 # dummy variable
set &iti 750 # inter trial interval (ITI)
set &nogodelay 250

bitmaps
frame
leftarrow
rightarrow
leftarrownogo
rightarrownogo
fixpoint1
fixpoint2
fixpoint3
wrongkey
shouldnothavepressed1
shouldnothavepressed2
shouldhavepressed1
shouldhavepressed2
instruction1
instruction2

fonts
arial 20

part nice_fixpoint
show bitmap fixpoint1
delay 75
show bitmap fixpoint2
delay 75
show bitmap fixpoint3
delay 75
clear -1 -2 -3
show bitmap fixpoint2
delay 75
clear -1
show bitmap fixpoint1
delay 200
clear -1

table gotable
"go left" leftarrow 1
"go right" rightarrow 2

table nogotable
"nogo left" leftarrow 1 leftarrownogo
"nogo right" rightarrow 2 rightarrownogo

task go
table gotable
set $trialcorrect 1
keys b n
show bitmap frame #1
delay 500
part nice_fixpoint # show nice fixpoint
show bitmap @2 # show the arrow (the go signal)
readkey @3 1000 # max response time 1000 ms
clear -1
### feedback
if STATUS == TIMEOUT
show bitmap shouldhavepressed1
delay 250
clear -1
show bitmap shouldhavepressed2
delay 250
clear -1
show bitmap shouldhavepressed1
delay 250
clear -1
show bitmap shouldhavepressed2
delay 250
clear -1
show bitmap shouldhavepressed1
delay 250
clear -1
error
set $trialcorrect 0
fi
if STATUS != TIMEOUT && STATUS != CORRECT
show bitmap wrongkey
delay 2000
clear -1
error
set $trialcorrect 0
fi
delay &iti
save @1 &d RT STATUS &d &d $trialcorrect

task nogo
table nogotable
set $trialcorrect 1
keys b n
show bitmap frame
delay 500
part nice_fixpoint
set $resttime expression 1000 - &nogodelay
show bitmap @2 # the arrow
readkey @3 &nogodelay # 'wait' until nogo delay is over
set $rt1 RT
set $status1 STATUS
## there are two possibilities:
## 1: Person has not yet responded
## 2: Person has responded, i.e., before stop signal, so that would be correct
if $status1 == TIMEOUT ### only if button NOT pressed show NOGO stimulus
clear -1
show bitmap @4 # the stop signal
readkey @3 $resttime # the remaining time up to 1000 ms
clear -1
fi
### now stimulus/response stuff done, check whether mistake was made
if $status1 == CORRECT
clear -1
set &nogodelay increase 50
fi
if $status1 != TIMEOUT && $status1 != CORRECT
show bitmap wrongkey
delay 2000
clear -1
set $trialcorrect 0
fi
if $status1 == TIMEOUT && STATUS == TIMEOUT
clear -1
set &nogodelay increase 50
fi
if $status1 == TIMEOUT && STATUS != TIMEOUT
show bitmap shouldnothavepressed1
delay 250
clear -1
show bitmap shouldnothavepressed2
delay 250
clear -1
show bitmap shouldnothavepressed1
delay 250
clear -1
show bitmap shouldnothavepressed2
delay 250
clear -1
show bitmap shouldnothavepressed1
delay 250
clear -1
set $trialcorrect 0
set &nogodelay decrease 50
fi
delay &iti
save @1 &nogodelay $rt1 $status1 RT STATUS $trialcorrect

block baseline
message instruction1
tasklist
go 20 allcorrect 50
end
feedback
text 0 0 "Average response time in milliseconds"
set &MyRT mean c4 ; postfix "ms" ; select c5 == 1
text 0 50 &MyRT ; postfix "ms"
end

block stopgo
message instruction2
tasklist
go 30
nogo 10
end



As can be seen in the attached image of the results, the tracking doesn't work.