5 greatest hits of neurocognitive methods for developmental research

Doing good research requires getting good data from the babies who come to visit us in the lab. Babies are wiggly and often have their own plans, so sometimes we need to get creative. Flexibility and highly specialised knowledge are the keys to getting the information we need. Happy baby = good data = happy researcher!

I recently went on a summer training course in Holland called “Neurocognitive Methods in Infant and Toddler Research.” Professionals and students came from all around the world to learn about the different ways we can get developmental data from little humans. Instead of sending YOU on a 5-day course, we decided to summarise the important bits here (with pictures)!


METHOD #1: Electroencephalogram (aka EEG)

The first method we learned is called ‘electroencephalography’ or ‘EEG’ for short. We’ve written a post about this method a while ago – you can check it out here to learn more.


EEG looks something like this, though this picture is a bit dated. Our brain’s cells, called neurons, fire in coordinated clumps that these sensors can measure. Measuring the clumps of firing neurons while baby watches movies, listens to sounds, or even interacts with others can tell us more about how baby is processing information from the outside world. Prof Emily Jones from the CBCD explained that you can measure 3 main things with EEG:

  1. Speed of processing, aka: when the baby begins to interpret the stimulus?

  2. Connectivity, aka: how are baby’s different brain regions working together during a task?

  3. Oscillations, aka: what are baby’s brain waves doing when they are working hard?

The brain signals we see from an EEG look something like this. Each line shows the brain wave data of one sensor. We can’t interpret much from data that looks like this. We can only draw conclusions from lots of data over lots of infants.


The EEG sensors look something like this. Each circle represents a sensor that is collecting data as demonstrated by a line on the chart with all the “blips.” There’s a lot to keep track of when you’re using this technique — you have to make sure all the sensors are picking up good data from baby’s head instead of random noise. It can be tricky! But with patience, careful attention, and lots of averaging over lots of participants, we can see how baby’s brain processes all kinds of things!


METHOD #2: Behavioural Techniques

Next, we learned about behavioural techniques from Prof Celeste Kidd of University of California, Berkeley. ‘Behavioural techniques’ is a fancy way of saying that we’re not looking at the brain at all but instead carefully observing baby’s behaviour during certain tasks.


One of my favourite techniques is called the ‘Violations of Expectation’ paradigm. Basically, we can assume that if a baby sees something they think is impossible, they should show a reaction of surprise. By looking for ‘surprise’, we can investigate what baby thinks is possible and impossible!


A lot of times, a baby shows surprise by increasing the amount that they look at a certain event. In this lecture, Prof Kidd reminded us to be careful when we make this assumption. At some ages and in response to some stimuli, babies actually show ‘familiarity effects.’ This means that they look more at things they prefer, such as mum compared to a stranger. Researchers who use behavioural methods like ‘surprise’ and ‘familiarity’ studies should always be careful about how they interpret the behaviours they observe.


METHOD #3: Eye-tracking

Now for eye-tracking with Jacco van Elst (see this past blog post about eye-tracking). Hypothetically, this one is really easy – all our kiddos need to do is sit in front of a TV screen and watch some cartoons. Sounds easy enough, right?


Well, the trick is that our TV screen measures the movement of baby’s eyes. In order for our screen to ‘see’ baby’s eyes, we need it at just the right height, distance, and angle. And, of course, baby squirms! Sometimes we need to adjust the TV screen as the experiment goes on in order to make sure we get the best quality data possible.


Well, the trick is that our TV screen measures the movement of baby’s eyes. In order for our screen to ‘see’ baby’s eyes, we need it at just the right height, distance, and angle. And, of course, baby squirms! Sometimes we need to adjust the TV screen as the experiment goes on in order to make sure we get the best quality data possible.


How exactly does the eye-tracker ‘see’ baby’s eyes? It depends on the eye-tracker. But the idea is that it measures the location of the whites of the eyes compared with the dark pupils. Then, when baby looks from left to right, the computer uses complicated algorithms to measure the distance between the start and end points. Crazy, right!? This gives us complicated (but cool!) data about how baby’s eyes scan whatever we put on the TV screen.


METHOD #4: Functional Near Infrared Spectroscopy (aka fNIRS)

This technique should be familiar to a lot of you as we have a lot of blog posts on it! You can reference Prof Sarah Lloyd-Fox’s work in The Gambia, Dr Carina de Klerk and Dr Chiara Bulgarelli’s descriptions of their preferred method, and Dr Evelyne Mercure’s research on language development. In this workshop, we learned from the magnificent Dr Carlijn van den Boomen. She described fNIRS in some warm, yummy terms with the example of a cup of tea.


fNIRS caps look something like this. It looks similar to EEG, right? The difference is that while EEG sensors measure the electricity generated by the brain over the scalp, fNIRS sensors shine tiny lights onto the scalp. Well, that’s not exactly true: half of the sensors shine tiny lights while the other half receive tiny bits of light. fNIRS lights are weak — they do not get hot or cause baby any discomfort. Imagine you have a clear cup filled with weak tea. If you shine a flashlight through it, some light will be absorbed by the tea and some will pass right through it, right? Now imagine you have another clear cup full of tea, but this cup is properly dark. If you shine a flashlight through this cup, less light will make it out on the other side, right? This analogy may seem overly simplified, but this is exactly how fNIRS works. Blood in active regions of the brain is called ‘oxygenated,’ meaning it contains more oxygen and is lighter in colour. Blood in ‘quiet’ regions of the brain is called ‘deoxygenated’ and is darker in colour. So, more light can pass through the oxygenated blood which is found in regions of the brain that are working hard. All that fNIRS does is send light into the brain and measures what light comes out. Based on these properties of blood flow, we can use fNIRS data to see what regions of the brain are active during certain tasks.


METHOD #5: Magnetic Resonance Imaging (aka MRI)

Last up on the course was Prof Manon Benders, an MRI specialist at UMC Utrecht. MRI is a less common technique for measuring infant development because they’re best used for long tasks with a still, calm participant — does this sound like any infants you know?! Still, some people do use it for developmental research: check out this blog post on adolescent research. MRI can be used in some cases, however, particularly when there is good medical justification for doing the scans.


MRI machines look like gigantic marshmallows. In order to get data from an MRI, the participant needs to lay still while their heads go into the gigantic marshmallow. The machine is essentially a big, loud magnet. Researchers often give baby two sets of earplugs to protect them from the noise! Then they get swaddled up and kept warm with many pillows and blankets. Once baby is warm, comfy, and soundly asleep, they don’t mind being in the big marshmallow at all! Surrounded by a team of specialists, they are entirely safe and tucked in for their scanning session.

MRIs give us beautiful pictures of the developing brain. Check out the differences between these brains at 1 week, 3 months, and 1 year! All of the white stuff shows neurons that are developing for specific purposes (e.g., language, vision, motor movements, and so much more). While these scans tend to be reserved for medical purposes because they are challenging to do, they can still give us a great idea about how the brain is wiring, changing, and specialising with time.


If you’ve made it this far, thanks for reading! You now know the basics of the most popular methods we use for infant and toddler research. We hope you keep learning about all the ways you can watch baby’s magnificent growth!


Author: Victoria Mousley


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