Sending Port Markers to Eyetracker Software with Inquisit

(I) Sending static markers (static = markers do not change values)

1) Create <port> elements

In order to send markers to eyetracker software (e.g. Tobii) to indicate the on- and/ or offset of stimuli, port elements for the markers have to be declared:

<port stimOnsetMarker> /*this marker sends value "1" to signal onset of stimulus
/port = eyetracker
/items = (1)
</port>

<port stimOffsetMarker>/*this marker sends value "0" to signal offset of stimulus
/port = eyetracker
/items = (0)
</port>

2) Include markers into relevant <trial> elements

The port elements then have to be included into the relevant trials.

<trial collectData>
/stimulustimes = [0 = stim, stimOnsetMarker; 1000 = eraseStim, stimOffsetMarker]
...
</trial>

(II) Sending dynamic markers (dynamic = markers can change value during runtime)

You can also dynamically set the value of your port markers.

Example:

You record participants' eye movements while they are looking at 2 different kinds of drinks; a soda can vs. a beer can. You test several different kinds of soda can images and several different kinds of beer can images and you counterbalance the screen positions of soda cans and beer cans.

You wish your marker to include information about stimulus positions and specific images presented.

1) Create <port> elements

<port dynamMarker> 
/port = eyetracker
/items = (0) /*this value will change during runtime
</port>

And add a value for the value that should be send as your marker:

<values>
/marker = 0
</values>

2) Create a numeric code that incorporates all the relevant info

For example (many different ways are possible - this is just one way), you could dynamically create markers of the following kind:" 015027"

0 = indicates start of left stimulus
1 = soda (Note: 2 would signal beer was the left stimulus)
5 = Next digits until 0 code the item number of left image
0 = indicates start of right stimulus
2 = beer
7 = Next digits until end code item number of right image

3) Create and include markers into relevant <trial> elements

<trial SodaBeer> /*trial to present soda can left and beer can right 
/ontrialbegin = [
	values.marker = "";				/*reset marker value
	values.marker = concat(values.marker, "01");	/*add '01' for soda is left 
	values.marker = concat(values.marker, picture.sodaLeft.currentitemnumber); /* add current itemnumber for left image
	values.marker = concat(values.marker, "02");	/*add '02' for beer is right 
	values.marker = concat(values.marker, picture.beerRight.currentitemnumber);	/* add current itemnumber for right image
	port.dynamMarker.setitem(values.marker, 1);	/*set the item for the marker you want to send 
]
/stimulustimes = [0 = sodaLeft, beerRight, dynamMarker] /*sends 015027 at stimulusonset
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</trial>