Running an EyeLink Study

Prepare the experiment before the caregiver and child enter the Eye-tracker room

• Turn on the light in the eyetracker room and leave the light intensity at the third point from the bottom.

• Turn on the display PC/Barcelona, the screen, the Eye-tracker PC and the speaker.

• Find your deployed experiment/order on the Barcelona computer.

• Launch the experiment by clicking on the eye icon and fill in the name of the experiment with the child ID, so instead of “Test.edf” you should write your participant ID for example “S001.edf”. Usually, we use S for "subject" and P for "pilot".

• Start the GoPro and check that has enough battery.

• Link the GoPro with the ipad using the GoPro Quik App. The Quik app will allow you to view the child from behind the curtains and record the session at the start of the study.

• Set up the iPod/MP3 and headphones with music for the caregiver

• Leave the child pillow ready in case you need it to raise young participants (you can place it in the parents' lap and sit the child on it).

Explain the study to the Parent while in the Playroom

• For example, "In this study we are interested in measuring word comprehension in bilingual children. To study that, we will show to your child pairs of images of two objects or animals on a screen, for example table and stroller (put an example but do not use any of the words we are using in the experiment). Then, a pre-recorded voice will ask the child to look at one of the objects in English or French. We are interested to see if your child can recognise the images. For that, we will be using an eye tracker, which has a camera with infrared light to track eye-movement. To be able to see where your child is looking, we will need to put a sticker on the forehead of your child. You and your child will go to a room and sit in front of a screen together. You can sit with your child on your lap or she/he can also sit alone on a high chair. Please, it is very important that you do not interfere at any time with the task, do not repeat any words or point at the screen. However, if you see your child looking somewhere else, you can bring back its attention to the screen by saying (“Look”). The study will take between 10 and 15 minutes. We can stop at any time if your child is not interested in the task. All the data that we gather today is kept confidential and fully anonymised. We will also be video recording with a camera your child. If you want us to stop the study at any point, simply raise your hand."

• Ask if they have any questions.

• Bring the caregiver and the child to the LWL room

• Bring the caregiver and child to the room where the LWL task is set up and ready to launch. Launch the experiment and start recording the session on the GoPro.

• Place the child in front of the screen and eye-tracker, usually children will be fine sitting on the lap of their caregivers but if not, let them sit on a high chair (you can also use the child pillow to raise very young children). Do all the adjustments needed so they are at the right distance from the Eye-tracker and the screen (you can move the arm to make adjustments). Put on the sticker to the child and use a child-friendly video clip to distract the child. If they have long hair covering the forehead you will need to use a pin to keep it away from the sticker. I usually touch the child’s head in various places so they do not know where I put the sticker.

• Look at the Eye-tracker screen to make sure they are at the right distance, their head appears centred on the Eye-tracker screen and the eye we are tracking is visible. Adjust the resolution of the Eye-tracker with the wheel under it until the eye is sharp. Adjust the CR and Pupil if needed.

• Once everything is ready, go behind the curtain and close it.

Start running the experiment

• Usually, the setup video will stop when you press “S”. Then the calibration instructions will appear on the screen. Press any key to continue. Then press “C” to start the calibration and the spacebar to agree to each point of the calibration. There are 6 calibration points and they need to form a perfect star once the calibration is done. If it is not like that, you can recalibrate by clicking “redo” on the calibration screen. Once you are happy with the calibration press “Enter” and then “O”, the experiment will start. You can also use the Validation function, before pressing "O", press "V" for validaiton, then "Enter" and finally "O" to start the study. If you need to skip the calibration because you are testing the task press “ESC” instead of “C”.

• Usually, you will be able to see the number of trials you are in on the eye-tracker screen.

• If you even need to cancel the task or close it before the end. Press “Control” + “alt” + ESC

• Some of these buttons might vary across experiments.

• During the whole experiment try to stay still to not distract the child with your presence. If needed, you can adjust the arm mount during the task but just if the child completely changes its position since you risk losing the eye and the calibration settings.

After the experiment

• On the eye-tracker computer, select “Camera Setup” if you need to run another participant. If not, select “Shutdown Host” and you will be able to switch off the Eyetracker computer.

• Write down all the details of the participant plus notes from the experiment. If you have done the calibration more than once, any issues...

• Extract the video from the GoPro and copy it in the Infant Database.