Millisecond Forums

The dragging feature in the ToL script works as follows:

Once you've selected one of the balls in <trial choice>, it executes a /branch to <trial move>. <trial move> is what chiefly implements the dragging feature. It accepts mouse movement and a left-click as response.

<trial move>
...
/ validresponse = (mousemove,lbuttondown)
/ branch = [if(trial.move.response=="mousemove")trial.move else trial.check]
</trial>

As long as the mouse is moved, <trial move> is repeated over and over again. If a left-click occurs, <trial check> is invoked, which (1) establishes whether the chosen action is valid (i.e., is there a free spot on the selected peg or not?) and if so (2) places the ball in the correct position.

Hope this helps.

Thank you for your help, but I think I am still a bit lost. Do you know of a less complicated task in the library that uses a dragging feature? It would be good if they had some more tutorials that were a bit more advanced perhaps.

No, there isn't a less complicated example in the library. If you can point out what exactly you're having trouble with, I'll gladly try to explain.

Here's a bare-bones, self-contained example illustrating the basic mechanics. It's just a few lines of code and, as you'll see, not hard to understand:

<values>
/ itemnumber = 1
/ x = 50%
/ y = 50%
</values>

<expressions>
/ xpct = 100pct*(trial.movemearound.responsex/display.width)
/ ypct = 100pct*(trial.movemearound.responsey/display.height)
</expressions>


<block myblock>
/ trials = [1=pickmeup]
</block>

<trial pickmeup>
/ ontrialbegin = [values.itemnumber=1]
/ inputdevice = mouse
/ stimulusframes = [1=blank, mystimulus]
/ validresponse = (mystimulus)
/ branch = [trial.movemearound]
</trial>

<trial movemearound>
/ ontrialbegin = [values.itemnumber=2]
/ ontrialend = [values.x = expressions.xpct; values.y = expressions.ypct]
/ inputdevice = mouse
/ stimulusframes = [1=blank, mystimulus]
/ validresponse = (mousemove, lbuttondown)
/ numframes = 1
/ branch = [if (trial.movemearound.response!="lbuttondown") trial.movemearound else trial.pickmeup]
</trial>

<text mystimulus>
/ items = ("Click me to pick me up.", "Click the left mouse button to put me down.")
/ select = values.itemnumber
/ size = (20%, 20%)
/ hposition = values.x
/ vposition = values.y
/ txbgcolor = red
/ erase = false
</text>

<shape blank>
/ shape = rectangle
/ size = (100%, 100%)
/ erase = false
</shape>

Thank you so much - I should be able to work from this to start making my task!

Charlotte

Could I just ask a few minor things?
1) why do you need the blank stimulus?
2) in trial.movearound. why do you put the '!' after trial.move.response.?
3) what are the expressions doing?


Thanks!!

C

> 1) why do you need the blank stimulus?

Otherwise you'd be seeing a trace of the stimulus' previous movements (it is set to /erase=false; if it were set to /erase=true, it'd be flickering). Try it for yourself.

> 2) in trial.movearound. why do you put the '!' after trial.move.response.?

"!=" is a negation. See the "Operators" topic in the documentation for details.

if (trial.movemearound.response!="lbuttondown") trial.movemearound else trial.pickmeup

means "if the response in trial movearound is *not* a click on the left mouse button, run trial moveraround again. Otherwise run trial pickmeup."

> 3) what are the expressions doing?

They convert the mouse x and y coordinates to screen percentages for convenience.

That's great thank you.
Now I have created my own file with a target and distractor picture. The participant should be able to choose either one and drag to a location. As the script is below - this only works when the choice of picture was the target. For some reason when you pick the distractor this also branches on to the trial.correctmove. Any ideas?

<values>
/ a = 50%
/ b = 40%
/ c = 50%
/ d = 60%
</values>

<expressions>
/ apct = 100pct*(trial.correctmove.responsex/display.width)
/ bpct = 100pct*(trial.correctmove.responsey/display.height)
/ cpct = 100pct*(trial.incorrectmove.responsex/display.width)
/ dpct = 100pct*(trial.incorrectmove.responsey/display.height)
</expressions>

<shape blank>
/ shape = rectangle
/ size = (100%, 100%)
/ erase = false
</shape>

<picture target>
/items = ("target1.tif")
/size = (100,100)
/hposition = values.a
/vposition = values.b
/erase = false
</picture>

<picture distract>
/items = ("distract1.tif")
/size = (100, 100)
/hposition = values.c
/vposition = values.d
/erase = false
</picture>

<text move>
/ items = ("Move target to correct location")
/position = (50, 50)
/ txbgcolor = red
/ erase = false
</text>

<trial choice>
/inputdevice = mouse
/stimulusframes = [1=blank, target, distract, move]
/validresponse = (target, distract)
/branch = [if(trial.choice.response!=target) trial.correctmove]
/branch = [if(trial.choice.response!=distract) trial.incorrectmove]
</trial>

<trial correctmove>
/inputdevice = mouse
/stimulusframes = [1=blank, target]
/validresponse = (mousemove, lbuttondown)
/numframes = 1
/ontrialend = [values.a = expressions.apct; values.b = expressions.bpct]
/ branch = [if (trial.correctmove.response!="lbuttondown") trial.correctmove]
</trial>

<trial incorrectmove>
/inputdevice = mouse
/stimulusframes = [1=blank, distract]
/validresponse = (mousemove, lbuttondown)
/numframes = 1
/ontrialend = [values.c = expressions.cpct; values.d = expressions.dpct]
/ branch = [if (trial.incorrectmove.response!="lbuttondown") trial.incorrectmove]
</trial>

<block one>
/trials = [1=choice]
</block>

I'm pretty sure <trial choice> should actually read

<trial choice>
/inputdevice = mouse
/stimulusframes = [1=blank, target, distract, move]
/validresponse = (target, distract)
/branch = [if(trial.choice.response=="target") trial.correctmove]
/branch = [if(trial.choice.response=="distract") trial.incorrectmove]
</trial>