Institute for Language Sciences Labs


Running a Baby EEG experiment

Last updated on 19 October 2021 by Ty Mees

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WARNING; Still a work in progress!

This protocol is written for researchers, research assistants and students who are planning to run EEG experiments with infants in the ILS Babylab. A PDF version is also available, which also includes a comprehensive step-by-step guide to analysing your EEG data. In addition, a less-detailed checklist version can be found here.

Should you have any questions or suggestions, please contact the lab taff.


A preliminary remark on how to treat electrodes with care

Before you start your first testing day, make sure you have read and understood this section carefully. Should you have any questions, please do not hesitate to ask!

Electrodes are very fragile and an entire electrode bundle may become completely useless once only one of the electrodes dies. The lifespan of electrodes can be shortened drastically when handled without care. Therefore, it is important to keep a few things in mind when working with electrodes.

  • NEVER let the electrodes touch metal. Always remove all of your jewellery before preparing the cap and cleaning the electrodes. Also, make sure your participant isn’t wearing any metal hairclips.
  • When preparing the cap, let the bundles hang around your neck to prevent the ends from touching the floor.
  • When cleaning the electrodes, make sure that the water is lukewarm. The gel will dissolve more easily when the water isn’t too cold, but too hot water will cause the electrodes to break faster.
  • Never let the electrodes lay in the water for too long; when you put them into the water, clean and (gently) dry them immediately.
  • NEVER let the other end of the bundle (which connects to the amplifier) touch water.
  • NEVER let the electrodes sit under running water.
  • Always clean the electrodes as soon as possible, before the gel gets the chance to dry.
  • Be sure that no gel is left behind on the electrodes.
  • Always clean the electrodes gently, using a soft brush. Don’t push or rub too hard.


The standard testing procedure

This section offers you a detailed description of how to run an EEG experiment with infants. In the lab, we make use of BioSemi equipment, and all experiments should be written in Presentation. Before you can start testing, make sure you have:

  • Approval of the ethics committee
  • Designed and piloted your experiment. NOTE: Make sure that all triggers are sent at the precisely right time from Presentation to Actiview!
  • Scheduled your participants
  • Reserved the EEG lab. There are two EEG labs at Janskerkhof 13: room K.13 and room K.02.

Note that a brief checklist of the entire procedure can be found here.



The Babylab waiting area

At the beginning of your testing day, make sure you open up the waiting area (room K.01) and turn on the light. Check if there is still water in the watering can, the kettle and the Nespresso machine, and if the plant needs watering. Also make sure that the room looks clean and tidy.
General instructions for correct use of the waiting area can be found here. NOTE: this document is password protected, please contact Desiree Capel for the login details.

The lab(s)

The ILS Labs has two dedicated EEG labs; the Baby-EEG lab in K.02 and the regular EEG Lab in K.13. Both labs can be used for EEG experiments with infants.

It’s recommended you use the same lab for the entire duration of your experiment, as the change in scenery might influence your results.

image 3.4
The control room in K.02 contains the following equipment:

  • Two computers (one for presenting the stimuli, circled in red in image 3 .4, and one for recording, circled in green in image 3 .4). You can find labelled stickers indicating which is which on the computers and screens.
  • An audio-interface labeled ‘Cabin Audio’
  • Headphones for listening to the parent in the test room (circled in yellow in image 3 .4).
  • A microphone for talking to the parent in the test room (circled in blue in image 3 .4).
  • A kitchen block, containing electrode bundles, electrode gel, caps and other EEG materials, and material for cleaning all equipment.

The test room (cabin) in K.02 (image 3 .6) contains the following equipment:

  • A high chair for children (might be in K.13 instead)
  • A chair for adults
  • A table
  • One monitor for the presentation of visual stimuli
  • Three speakers for the presentation of auditory stimuli (either stereo left/right or mono-center)
  • A webcam (circled in red in image 3 .6)
  • A pair of headphones for masking the parent (circled in green in image 3 .6)
  • A closet containing the BioSemi amplifier, a measuring tape and EEG caps (circled in blue in image 3 .6)


  • Turn on both computers. Make sure they start up in the right mode:
    • Recording PC: Linux;
    • Presentation PC: Windows if using Presentation, Linux if running Zep.
  • Turn on the speakers in the cabin by turning on one of the plug boxes on the right side of the table in the cabin. You can choose between stereo audio from the side speakers and/or mono audio from the center speaker.
  • On the Recording PC: start the program OBS Studio. Check the position of the webcam.
  • If the child needs to watch a DVD at some part during the experiment: insert it into the Presentation PC. Open the DVD in VLC Media Player and drag it to the correct screen in the test room.

image 3.6

image 3.1

The control room in K.13 contains the following equipment:

  • Two computers. You can find labelled stickers indicating which is which on the computers and screens.
  • Two screens for the left computer (numbered ‘1’ and ‘2’ in image 3 .1)
  • Two screens for the right computer (numbered ‘3’ and ‘4’ in image 3 .1)
  • One webcam monitor (numbered ‘5’ in image 3 .1)
  • One Tangent amplifier (circled in green in image 3 .1)
  • One audio switch box (circled in blue in image 3 .1; enlarged in image 3 .3)
  • One video switch box (circled in red in image 3 .1; enlarged in image 3 .3)
  • Two remote controls (image 3 .2)

The test room in K.13 (image 3 .5) contains the following equipment:

  • A high chair for children (might be in K.02 instead)
  • A chair for adults
  • A table, covered with soft material to mute the sound of toys that are smashed onto the table
  • One monitor for the presentation of visual stimuli
  • Two speakers for the presentation of auditory stimuli
  • A webcam (circled in blue in image 3 .5)
  • A plastic cabinet (circled in green in image 3 .5), containing the BioSemi amplifier, head caps, electrode stickers, cotton pads and alcohol
  • A kitchen block, containing material for cleaning all equipment, electrode bundles (circled in red in image 3 .5), electrode gel and spare materials.
  • An air humidifier (circled in yellow in image 3 .5, enlarged in image 3 .10)
  • A decibel meter (next to the orange arrow in image 3 .5, enlarged in image 3 .8)

image 3.5


  • Turn on the main power switch on the right of the desk in the control room.
  • Turn on both computers.
  • On the recording PC: start the program OBS Studio and check if the webcam is working.
  • Turn on the Tangent amplifier by pressing the power button on the left hand side.
  • Set the audio switch box to ‘T’ (Tangent amplifier; circled in green in image 3 .3).
  • Set the video switch box to the correct screen by clicking either one of the two buttons circled in purple in image 3 .3. The left button is to select screen number 1 (in image 3 .1), the right button is to select screen number 3 (image 3 .1). The green light, circled in yellow in image 3 .3, indicates which screen is selected. The selected screen will be on the screen in the test room, and will be visible for the participant.
    • If the child needs to watch a DVD during the experiment, insert the DVD into the computer on the left hand side. Select screen number 1 using the video switch. TODO: Left side? It’s upside down 😮
    • If the experiment contains visual stimuli in Presentation, select screen number 3. If the child needs to watch a DVD with sound, also select screen number 3 and insert the DVD into the computer on the right hand side. TODO: same stuff

image 3.3

General preparation

From the kitchen block in the control room (K.02) or the plastic cabinet next to the table (K.13), get out the following items:

  • Electrode stickers (‘1’ in image 3 .7)
  • Cotton pads (‘2’)
  • Alcohol (‘3’)
  • Electrode gel (‘4’)
  • A syringe (‘5’)

Place all items on top of the cabinet/table in the test room.

image 3.7
Next, consider whether you want the child to sit in the baby chair, or whether you want it to be on the parent’s lap, for instance if it’s too young to sit down independently. Place the chairs according to your decision. Make sure that the child is seated right in front of the screen, in the middle of the two speakers. When testing in K.02, turn on the two speakers and the display(s) that you’re going to use by pushing the on/off-buttons. Keep the other displays turned off. When testing in K.13, check if the table is covered with the towel.

Once everything is prepared, start the experiment on the Presentation computer and check the sound level. There is a decibel meter on the shelf in the test room in K.13. Hold the tip of the decibel meter (circled in yellow in image 3 .8) at the place where the child’s ear will be during the experiment, and turn on the device using the switch circled in red in image 3 .8. You will see a number starting around 110 on the screen of the device, which will drop slowly until it keeps on circling around a certain number. This is the current sound level. The desirable sound level is approximately 65 decibel. If it is too high or too low, change the sound level in your experiment. For more information on how to use the decibel meter, please see here.

image 3.8

Changing the sound level in Presentation

If, after checking the sound level with the decibel meter, you find that the sound level is too high or too low, there are two ways to change the volume when using Presentation. Depending on your settings in Presentation, you could do it in either one the following manners.

One way to change the sound level, is to change the volume of the Presentation computer in the lower right corner of your screen (as you usually change the volume). This will work, as long as you haven’t installed a fixed sound level in your Presentation experiment. If you notice that the volume automatically jumps back to the original sound level after restarting the experiment, you need to adjust the volume in Presentation itself.

To do this, open up your experiment and go to the tab ‘Settings’ (circled in green in image 3 .9). On the left hand side, go to ‘Audio’. You will see the audio settings appear. Underneath ‘Volume’, you will probably see that the checkbox in front of ‘Set Device and Application Volume Device Volume’ is checked (circled in blue in image 3 .9). Adjust the sound level by typing in a higher or lower number between 0.0 and 1.0 in the square circled in red and click ‘Apply now’. Restart the experiment and check the sound level again. You should now see that the volume has changed.

image 3.9

Air circulation

When testing in K.13, you’ll find an air humidifier next to the kitchen block (image 3 .10). This device secures a pleasant air humidity inside the test room, to make sure that participants don’t blink their eyes too much.
Before you start testing, remove the entire grey part from the white part by lifting it up. Fill up the white box with water until the water level reaches ‘max’ (you can check the water level by looking at the indicator circled in red in image 3 .10). Put the grey part back on again, plug the humidifier in and press ‘power’ (circled in green).

image 3.10

The cabin in K.02 is connected to the buildings air circulation system, no setup is needed. The control room can be ventilated by using the fan in the window. The controls for the fan are located on the left wall next to the window, and consist of a on/off switch and a speed control. (Note: you might also need to pull the cord on the fan itself if someone used that by mistake).


Receiving the participant and preparing the cap

After you have prepared the control and test room, it is time to receive the parent and the baby in the waiting area. In the waiting area, shortly explain what is going to happen and let them sign the informed consent form. Take them to the EEG lab. Once they are seated, you can start the preparation of the cap.

Apply gel on the baby’s wrist

Before doing anything at all, apply a little bit of gel on the baby’s wrist using the syringe. Tell the parent that you’re doing this to make sure there won’t be an allergic reaction to the gel. You can show them that the syringe won’t hurt the child, by tapping the tip of the syringe onto your own palm. Tell the parent that the chances of getting an allergic reaction are extremely small, due to the fact that the gel is basically only a combination of water and salt.

Explain the procedure

While giving the baby’s skin a chance to react to the gel, explain the procedure to the parent. Mention the following things:

  • What the experiment is about
  • A brief explanation of the EEG procedure
  • The duration of the actual experiment
  • What the child is and isn’t allowed to do (e.g. play with the toys)
  • Tell the parent not to speak during the experiment
  • Also tell the parent to try to prevent the baby from pulling the cap or the electrodes as good as they can.
  • Ask the parent to switch their phone to airplane mode, otherwise its signals will interfere with the EEG.
  • Let them know that they are being watched through the webcam, and whether there will be a video recording of the experiment.
  • If they want to stop the experiment, for whatever reason, they can wave to the camera.
  • If the baby becomes too restless, you can stop at any time.
  • They can wash their baby’s head at the end of the experiment.

After the explanation, check the baby’s wrist once more. If the skin hasn’t reacted to the gel, proceed with the preparation. If there seems to be an allergic reaction, quit the experiment.

Applying the mastoid electrodes

Before placing the cap on the child’s head, you have to apply the ‘mastoid electrodes’. These electrodes are also indicated by the names ‘EXG1’ and ‘EXG2’ (or EX1 and EX2; see image 3 .12). These are two separate electrodes, and are not part of a larger bundle.

The mastoid electrodes have to be placed behind the ears of the infant, on the ‘mastoid’. This is the most bony area behind the ear, where presumably no (or few) signals from the brain are received. In an EEG experiment, all electrodes on the left hand side are usually indicated by an odd number, and all electrodes on the right hand side are usually indicated by an even number. This means that EXG1 has to be placed behind the left ear, and EXG2 has to be placed behind the right ear of the child.

image 3.12

image 3.13

image 3.14

When applying the mastoid electrodes:

  • First, put a little bit of alcohol onto a cotton pad (numbered ‘2’ and ‘3’ in image 3 .7).
  • Degrease the area behind the child’s ears by rubbing it gently with the cotton pad with alcohol.
  • Take one of the electrode stickers (numbered ‘1’ in image 3 .7).
  • Stick it onto the electrode (as in image 3 .13).
  • Remove the white protection layer (as in image 3 .14).
  • Add a little drop of gel in the circle in the middle (as in image 3 .15). Do not forget to do this! It will hurt the child if you forget to add gel. However, also make sure you don’t add too much gel.
  • Try to feel with your fingers where the mastoid is located and stick the electrode onto the mastoid (image 3 .16).
  • Insert the other end of the electrode into the BioSemi amplifier (circled in blue in image 3 .20
  • Watch out that the child doesn’t pull off the electrode right away!

image 3.15

image 3.16

NOTE: You can also prepare the cap first, and try to squeeze the mastoid electrodes underneath the cap afterwards to make sure the child cannot pull them off right away. A disadvantage of this method is that it’s harder to find the right location of the mastoids when the cap is already on the head. The importance of the mastoid electrodes also depends on whether you will use the linked left and right mastoid as reference for offline processing. Average reference may work fine. If you use the average as a reference, you don’t necessarily need the electrodes on the left and right mastoid (for more information about referencing your data, read this section).

Preparing the cap

After you have adjusted the mastoid electrodes, take out a cap in a size that fits the baby’s head circumference. There are several cap sizes available, that can be distinguished by colour.
The available cap sizes can be viewed here.

Which size you need, can primarily be based on the age of the infant. If you have an indication of the average head circumference of the age group you’re testing, you won’t have to measure every infant’s head beforehand. There are plenty of online guides which predict the infant’s head size, for instance this one, which also allows you to make a prediction based on gender. It is still recommended to measure the head though, because not every child is the same. To measure the head of the child you can use the yellow measuring tape from one of the plastic cabinets (K.13) or from the kitchen cabinet (K.02).

After you’ve decided which cap to use, try to put on the cap in one go. Do it fast and try to avoid having to adjust the position of the cap too much, because it might upset the baby. Make sure that Cz is right on top of the head, in the exact middle between the ears and between the tip of the nose and the back of the head. The Fp-electrodes should be in the front; the O-electrodes should be at the back of the head. Take the ears through the little holes (only if it is possible) and fasten the cap with the Velcro.
Next, fill up the syringe with gel and put a little bit of gel into each electrode (image 3 .17). Make sure the gel touches the scalp, so that a good connection can be made, but be gentle with the baby’s head.

image 3.17

image 3.18
Take one of the 32-electrode bundles (indicated with only a letter and no numbers at the beginning of the strap). Insert all electrodes into the corresponding holes in the cap, indicated by letters, numbers and colours (image 3 .18). Start with the electrodes closest to the BioSemi amplifier, and end with the ones furthest away to avoid the electrodes from getting tangled. When looking at the electrode bundle, you will see that one side has a red edge (indicated with an arrow in image 3 .19). By beginning with this side, you will start with the electrodes on the left hand side (odd numbers). By beginning with the other side of the bundle, you will start with the electrodes on the right hand side of the cap (even numbers).

After you’ve inserted all electrodes into the cap, insert the other edge of the bundle into ‘A1’ on the BioSemi amplifier (circled in green in image 3 .20). Press until the plastic white ‘wings’ on either side come up. Turn on the amplifier by pressing the button circled in red in image 3 .20. A blue light, as circled in yellow in image 3 .20, should start to burn continuously. If the light flickers, this means that the electrodes CMS and DRL aren’t attached properly and may
need more gel. Keep on adding more gel and pressing the cap to the head until the light stops flickering.

NOTE: Good signal from CMS and DRL is very important. If these two are not well connected, your signal will be messy and not usable!

image 3.20

When testing an infant, there are two ways to prepare the cap: directly on the infant’s head (as described above), or by preparing it before the participant arrives. Both methods have several advantages and disadvantages. Preparing directly on the participant’s head allows for using a better cap size, because you can choose the cap size after you’ve seen the baby’s head, but will require a lot of patience and cooperation from the infant as you adjust the electrodes one by one on its head. Preparing before the appointment is a faster, but also more sensitive option as you won’t know the baby’s head size or amount of hair before the appointment. This may result in having to prepare directly on the infant’s head after all, if there are too many errors to start the experiment. Also, note that after a certain age, the signal will become too noisy when preparing the cap before the appointment, due to the development of a thicker skin. Read this section to see which method works best for which age group.

If you decide to prepare the cap before the participant arrives, you can use a small ball (e.g. from Action) on a non-metal object (such as a porcelain teapot) as a substitute for the infant’s head. Place the cap inside out on the ball (as in image 3 .21). Insert gel into all holes using the syringe (as in image 3 .22). Fill the holes all the way to the edge, to make sure a decent connection can be made.

Next, turn the cap inside out again (image 3 .23). Take out the 32-electrode bundle and insert all electrodes in the corresponding holes (image 3 .24). Start with the side that will be closest to the BioSemi amplifier.

image 3.21

image 3.22

image 3.23

image 3.24
Turn the cap inside out again, and add a little more gel to all electrodes in the same way as in image 3 .22. Leave the cap like this until the participant has arrived.

After you have received the parent and the baby, follow the first part of the procedure as described above (apply the gel on the wrist, explain the procedure, apply the mastoid electrodes). After you’re finished, adjust the prepared cap onto the baby’s head in one go. Do it as fast and precise as possible to try to prevent the baby from getting upset. Also, make sure that the position of the cap is immediately right, as adjusting it may cause a connection between electrodes because of the gel. Make sure that Cz is right on top of the head, in the exact middle. The Fp-electrodes should be in the front; the O-electrodes should be at the back of the head. Take the ears through the little holes and fasten the cap with the Velcro. Stick the other end of the electrode bundle into the BioSemi amplifier (circled in green in image 3 .20). Turn on the amplifier and check if the blue light isn’t flickering (circled in yellow in image 3 .20).

Checking the signal


After all the electrodes are adjusted properly, it is time to check the signal. The first check is the blue light on the BioSemi amplifier (circled in yellow in image 3 .20). If this light is flickering, it indicates that the electrodes CMS and DRL are badly connected. These electrodes do not give you data, but form a feedback loop which acts as a reference and reduces the noise. Without a good CMS/DRL connection, your EEG measurements will be useless. Therefore, always make sure the blue light on the BioSemi is stable.


After making sure that the CMS and DRL are working properly, it is time to start ActiView. Open up ActiView on the EEG1 (K.13)/Recording (K.02) computer. Before you start recording, make sure you have loaded the correct configuration file. A pop-up will open automatically in which you can select the correct configuration file. Go to ‘Desktop’, click ‘Configuration file’ and select ‘Infant_32channels.cfg’.

On your monopolar display, press ‘start’ (circled in yellow in image 3 .25). You will find that for each selected electrode, the signal is displayed on the screen (circled in red). Set the reference to Cz, by selecting ‘Free choice’ under ‘Reference’ (circled in green in image 3 .25) and selecting Cz in the list underneath. Check the signal for each electrode. The flatter the signal, the better. If you notice that one or more signals are very noisy, try adding more gel to that particular electrode, but not too much as you don’t want two electrodes to be connected through the gel. If you find that all signals are extremely noisy, add more gel to CMS and DRL or press the cap a little firmer onto the head with your hands. If the overall signal is better when you don’t select Cz as your reference, consider adding more gel to Cz. If you’ve tried to add gel to an electrode for a maximum of three times without seeing a significant improvement, remove the electrode from your display. You can do this by selecting ‘Free Choice’ under ‘Channels’ (circled in orange in image 3 .25, enlarged in image 3 .26), and deselect the particular electrode by pressing CTRL and selecting the channel from the list underneath. The data for this channel will still be saved, even though it is removed from the display.

image 3.25

image 3.26
While checking the signal, also look at the impedance by clicking ‘Electrode offset’ in the toolbar. Set the displayed range to 50 mV (circled in yellow in image 3 .27). You should see that the bars turn to blue. All bars should be within the range of +25 mV and -25 mV. The closer to zero, the better the signal. If one of the bars is above +25 mV or below -25 mV (for instance the bars circled in red in image 3 .27), consider adding more gel to the corresponding electrode. If you see that one of the bars is very unstable, also consider adding more gel to that particular electrode or remove it from the display.

NOTE: it may be difficult to get all electrodes with good signal when testing infants. Researchers are usually only interested in some electrodes rather than all. For instance, MMN is mostly visible at frontal-central electrodes. Hence, if the electrodes at the parietal and occipital locations are noisy, it is not worth it to spend a lot of time adjusting these electrodes, as children very easily get annoyed by people working on their head. Researchers need to be aware of the trade-off between a very good signal and crying babies. In addition, if you use left and right mastoids as reference, a few noisy electrodes can be tolerated, but if you want to use average reference in offline processing, decent signal from all electrodes is needed, otherwise your reference will not be accurate.

image 3.27



Start recording (Recording computer)

After you have checked the signal and everything is looking as good as possible, it is time to start testing. Close the door between the test room and the control room. NOTE: The cabin door in K.02 doesn’t close easily, so you might need to apply a bit more force than usual.

Press ‘Start File’ in the bottom right corner of ActiView (circled in blue in image 3 .25). A dialog pops up in which you have to type the participant number (image 3 .28). Type your participant number in the box under both ‘Enter Local Subject Identification’ and ‘Enter Local Recording Identification’. Press ‘OK’. After this, you will be able to select a folder in which you want to save the recording, type the same participant number again as the file name. Click “OK”.

NOTE: After you’ve pressed OK, you are not recording yet! Click ‘Pause Save’ at the right bottom corner of the screen when you want to start your recording. The buttons should look like the ones in image 3 .29, otherwise you are not recording!

Start experiment (Presentation computer)

Once you’ve made sure that you are actually recording, start your experiment in Presentation on the EEG2/Presentation computer. Click ‘run’, type in the participant number and press ‘enter’. Keep on pressing ‘enter’ until the sound starts playing.

Return to the ActiView screen and check whether the triggers are sent. You can see this in the window circled in red in image 3 .30. A colour or number should appear (depending on your settings) every time a stimulus is played. You can adjust the settings by selecting something else in the window circled in green in image 3 .30. This will not affect your data, but will only change your current view. If you do not see any triggers appear, stop the experiment and call lab support. Without triggers being sent, no offline processing can be performed, so you are recording for nothing!
You can always stop the experiment in Presentation halfway by pressing the Esc button. This will stop the entire block you were running. If a block has ended, press ‘enter’ a few times again to proceed on to the next block. It won’t be possible to pause a block and continue later. However, you can restart a block by starting the experiment again and skip the previous blocks (press ‘enter’ and ‘esc’ right after each other when starting a new block). Keep in mind that the log files from your experiment will overwrite themselves when restarting the experiment. If you want to keep those, make sure to copy them before you restart your experiment.

image 3.30
Once the recording has finished, press “pause save” at the right bottom of the screen, and then press “stop” at the up left of the screen.



After you completed the testing phase, remove the cap from the infant’s head and take off the mastoid electrodes. Guide the parent and child to the washing room and show them the towels and shampoo, or give them a Zwitsal paper cloth if they don’t want to wash the hairs immediately (this is usually enough cleaning for the youngest children without many hairs). Before you say goodbye to the parent and child, take them back to the waiting area and give them a gift (usually a book that’s appropriate for the child’s age) and reimburse travel expenses (if applicable). For more information about this, read the waiting area protocol. Also, give the parent the opportunity to ask any questions they may have.

Afterwards, fill the two plastic washtubs with lukewarm water (image 3 .31). Remove the electrodes from the cap and gently place them into the water. Do not let the electrodes sit under running water! Use the softest toothbrush to gently clean the electrodes. Pat dry them with a piece of paper towel. Hang the bundle back to it’s place and put the end with the electrodes back in the bag to prevent them getting (sun)light; image 3 .32 image 3 .32).
Place the cap in the other washtub. Use the other brush to remove the gel from the holes in the cap. Hang the cap up to dry on one of the hooks above the sink.
Fill the syringe a few times with lukewarm water and press it empty to remove the gel in the tip.

image 3.31 image 3.32



After a few appointments, you may get an error message in ActiView stating that your battery is low. There is always an extra battery in the control room, which should be connected to the charger.
The battery of the BioSemi amplifier is the large block underneath the block in which you plug in the electrode bundles (image 3 .). First, remove the cable circled in red in image 3 . by pulling it out. Then remove the cable circled in green, by (gently) pushing and turning it. Disconnect the battery from the amplifier by clicking all four black locks sideways and up. Take the battery to the control room.

image 3.33

In the control room, you’ll find a spare battery and the charger (image 3 .). Connect the empty battery to the charger by connecting the blue parts (circled in green in image 3 .) and plug the charger into the socket. Take the spare battery back to the amplifier and connect it to the amplifier by adjusting the two cables and the four black locks again.

image 3.34

Testing infants may be quite challenging and approaches can differ widely as infants grow older. Therefore, it is always necessary to search for the correct approach when starting an experiment with a new age group. So far, we have personally experienced what it’s like to test 4-, 12- and 20-month-old infants. In this chapter, we’d like to share our experience and provide certain guidelines on how to deal with these age groups. Note that no matter the age group, a bubble blower will make all children happy. Use this as your first choice munition in any bad situation.

How to test 4-month-olds

At 4 months, infants have just gained control over their heads and cannot sit down properly yet. Therefore, they have to sit on their parent’s lap during the experiment instead of in a high chair. A problem with this, however, is that infants tend to lean against their parent’s stomach, which may cause a lot of noise in the signal. Ask the parent explicitly to prevent this as much as possible. Because their motor skills haven’t quite developed yet, you won’t have to worry about them wanting to run away from the table. Instead, there’s a big chance that the child will cry during the experiment. If it does, try distracting the child, for instance with a bubble blower. If this doesn’t work, check with the parent whether it may need something. The child may be hungry or may need a diaper change, which are problems that can easily be solved after which you can continue the experiment. If the child is tired, however, it will be more difficult to continue the experiment and you may want to consider aborting it.

As far as the preparation of the cap is concerned, our experience is that the preparation before the appointment works best for 4-month-olds. Preparation directly on the infant’s head can take quite a long time, and 4-month-olds tend to get restless pretty quickly. Also, the signal of the pre-prepared cap is quite similar as to the one that’s prepared immediately onto the infant’s head. Preparing the cap before the appointment therefore saves a lot of time and frustration for the child. You can apply the mastoid electrodes first, and then put the prepared cap onto the head in one go. Make sure you immediately get the position right, as readjusting it may cause bridges between two electrodes.

Best cap size: blue/pink

How to test 12-month-olds

At 12 months, infants have gained a lot more motor skills already and some may have even started walking a little bit. This can be pretty cute, but the consequence of this is that they also want to move around and explore during your experiment, whereas you really want them to sit still. Make sure there is enough distraction for them as you put the cap onto their heads. You could for instance play Dora the Explorer on the screen, or have toys on the table for them to play with. If the infants aren’t allowed to play during the experiment, however, be careful when providing them with toys, as they may get upset when you take the toys away from them before the experiment starts. Instead, choose to play something fun on the screen.

For this age group, it also works best to prepare the cap in advance, to make sure they don’t have to sit still for a long time as you prepare the cap onto their heads. Be careful though with children who already have a lot of hair, as it may be more difficult to get a clean signal this way.

Best cap size: blue

How to test 20-month-olds

At 20 months, infants can already walk and they have started talking a little bit. You will notice that these children also have become much more aware of what is happening to them, and differences in character will be clearly visible. The word ‘no’ is especially well-known, and they won’t think twice about using it whenever they can. At this age, it is far more important to talk to them directly as opposed to the younger infants. Whereas you could still put the cap onto their heads without saying anything when they were just 12 months old, they now demand an explanation and a certain degree of autonomy from you. Below, you will find an overview of the tricks we used while testing 20-month-olds:

  • Make the EEG caps look more child friendly, for instance by giving all the stuffed animals in the room an EEG cap as well.
  • Decorate two caps of the correct size with child friendly figures, for instance flowers and stars, and let them choose which cap they want to put on their head. Make them believe they have a choice in the matter.
  • As soon as the child walks into the room, point your attention directly to the child and explain to the child that all their stuffed animal friends wear beautiful caps, and they want to play a game with the child, but then the child gets to wear a cap too. Explain to them that they can choose which cap they want. Always be enthusiastic and point out all the nice things about wearing a cap.
  • If the child is very shy or actively refuses to make a decision, take more time for this part and try to involve the parent. For instance, ask the parent if they also want to wear a cap, or put one on your own head as well to show the child it isn’t harmful. Another thing you can do is let the child choose if either you or the parent should put the cap onto the child’s head. Make sure you instruct the parent on how the cap should be placed.
  • Once you have tricked the child into wearing the cap, first clean their skin behind the ears with alcohol before you proceed to put the cap onto their head. As soon as you have put the cap on, start a video with children’s songs to distract the child immediately. Our experience is that they will totally forget that they have something on their head as soon as they hear the songs.
  • While the infant is listening to the children’s songs, you can put a little bit of gel onto the child’s wrist, explain to the parent what you are going to do and afterwards check the child’s wrist again for any allergic reactions. If there aren’t any, you can start the preparation of the cap by inserting the gel into the holes.

Note that preparing the cap before the appointment does not work for this age group, as their scalp has become thicker and they have gained a lot more hair. Therefore, more distraction is needed to keep them from getting upset while undergoing the preparation.

Best cap size: green/blue for girls, green for boys