This toolbox allows Matlab users to interface with Gazepoint eyetrackers.
The simplest way to implement this toolbox in your Matlab/Psychtoolbox experiments is to use Example_Script.m as a template.
- Install the Gazepoint applications from this link (https://www.gazept.com/downloads/). Then, download the gazepoint-matlab-toolbox and save the functions found in GP3_Functions in the directory or a sub-directory of your main experiment script.
- At the beginning of your main experiment script, include the following lines of code to set up connections with the GP3 eye-tracker. The ConnectToGP3 function creates a socket connection with the GP3 server in the main Matlab session (session1). This session1 socket is used to send synchronization triggers from the experiment script to the eye-tracking data stream. The ExecuteRecordGP3Data function spawns a new Matlab session (session2) and creates another socket. The session2 TCPIP socket reads the eye-tracking data from its input buffer and stores the data in a text file.
%% Set-up Matlab to GP3 session1 socket session1_client = ConnectToGP3; %% Spawn a second Matlab session2 that records GP3 data to output file outputFileName = 'example_output.txt'; ExecuteRecordGP3Data(session1_client,outputFileName);
- In the stimuli presentation body of your main script, it's important to embed synchronization messages in your eye-tracking data stream. Mark any event of interest by including the SendMsgToGP3 function in your script. For example, you may want to send a message trigger at the start of a new trial, at the onset and/or offset of a stimuli, or after a participant button response.
%% Experiment (stimuli presentation) goes here for trial_num=1:5 % Start of new trial here SendMsgToGP3(session1_client,['trial_start' num2str(trial_num)]); %send msg trigger for start of the trial pause(2); % Present a stimuli here SendMsgToGP3(session1_client,['stimuli' num2str(trial_num)]); %send msg trigger for onset of new stimuli pause(2); end
- After the behavioral experiment completes, tell the session2 socket to stop collecting data.
%% Stop collecting data in session2 socket SendMsgToGP3(session1_client,'STOP_EYETRACKER');
- Finally, close the session1 socket.
- You're now ready to run your experiment script with eye-tracking! Before running the Matlab script, remember to first start up the Gazepoint application.
Configuring the Eye-tracking Data Stream
The ExecuteRecordGP3Data function gives you the option to configure the eye-tracker data stream to your specifications. To do this, pass each of the desired data type keywords as strings when you call ExecuteRecordGP3Data in your script. If no optional variables are passed, the default data stream configuration includes Left Pupil, Right Pupil, and Blink data (the values that I'm most interested in). The comprehensive list of data type keywords can be found in the Gazepoint API (http://www.gazept.com/dl/Gazepoint_API_v2.0.pdf). For instance, if I want the data for Right Pupil Data and Best POG: