The Inquisit SR Research Plugin

The Inquisit SR Research Plugin enables integration of Inquisit scripts with gaze point and pupil data from SR Research's EyeLink eye trackers. The plugin enables gaze-contingent tasks along with sending rich metadata to the eye tracker to indicate visual events, trial variables, participant responses, and custom event markers.

Registering the Plugin

The Inquisit SR Research Plugin includes a 30-day free trial that begins when Inquisit is installed. After the trial period ends, a license is required to use the plugin. Once you purchase a license, you can register it by selecting the "SR Research Registration..." command from Inquisit's Help menu. The registration window will appear with instructions for completing the registration. If you wish to move the license to a new computer, you can login to your account on millisecond.com and submit a transfer request.

Programming the Plugin

To record and utilize gaze point data from an SR Research eye tracker, you must first declare the eyetracker element in your script and and set the plugin to "srresearch":

<eyetracker>
/ plugin = "srresearch"
</eyetracker>

Once the eyetracker is defined in the script, whenever the script is run Inquisit loads the plugin and attempts to locate the SR Research eye tracker on the network. Once connected, the plugin runs the calibration procedure and then interacts with the eye tracker according to the commands in the Inquisit script. Recording of gaze point data for a given trial can be enabled using the datastreams or inputdevice commands on the trial element. For dynamic procedures that change based on gaze point data, you can programmatically access gaze point data from the properties of the eyetracker element.

Using gaze data as response input

The plugin enables you to define trials in which gaze is treated as a response similar to a mouse click. For example, in a parafoveal priming paradigm, participants could be instructed to focus on a fixation point stimulus. When the eye tracker reports a fixation on the stimulus, it is logged as a response, and the prime stimulus is presented. As shown in the example below, this is accomplished by setting the inputdevice attribute to "eyetracker" and defining the fixation stimulus as a "validresponse".

<trial fixation>
/ stimulustimes = [1=fixation]
/ inputdevice = eyetracker
/ validresponse = (fixation)
/ branch = [trial.presentstimuli;]
</trial>

Supplementing manual response tasks with gaze point data

Eye tracker data can also be used with task that require other modes of responding such as mouse or keyboard. For example, imagine you wish to collect gaze point data to uncover how gaze affects memory performance on the Corsi Block Tapping Test. As show in the example below, this can be accomplished using the datastreams attribute, which causes the eyetracker to record gaze point data for the duration of the trial.

<trial showseq>
/ stimulusframes = [1=board,1,2,3,4,5,6,7,8,9]
/ validresponse = (noresponse)
/ trialduration = parameters.tapinterval
/ posttrialpause = parameters.posttapinterval
/ branch = [if(values.tapcount < values.seqlength) trial.showseq else trial.recallseq]
/ recorddata = false
/ datastreams = eyetracker
/ screencapture = true
</trial>

Sending stimulus data to the eye tracker

Inquisit automatically sends meta data about all visually presented stimuli to the eye tracker without requiring any special programming. For all visual stimuli, Inquisit notifies the eye tracker of the stimulus onset time and defines their screen regions as areas of interest. For picture stimuli, Inquisit also sends the file name so the images can be loaded by Data Viewer into their corresponding screen positions, and gaze points can be plotted over them. If you wish to replay entire sequences of stimuli in Data Viewer, all stimuli shoudl be defined as pictures.

If the screencapture attribute is set to true on the current trial, the screen as it appears at the end of the stimulus presentation sequence is captured to an image file. The name of the file is sent to the eye tracker and "back dated" to the start of the trial. This enables gaze points to be plotted over the entire screen (including presented text and shapes) within Data Viewer. Note that since the screen capture is just a static snapshot of the end result of all stimuli presented by the trial, it does not include temporal information to support the playback of a trial within Data Viewer. If playback is required, screen capture should be disabled, and the Inquisit script should present all visual stimuli (text, shapes, etc.) as images using the picture element.

The Eye Tracker Element

Sample Scripts

Sample scripts for the SR Research Plugin can be downloaded from the Millisecond Test Library.