How motion capture is providing greater insights into infant behaviour – Dr. Kim Duffy

While motion capture technology was first used within the life sciences industry for gait analysis in the early seventies, biomechanics research is still the technology’s most common application today.

But the power and capabilities of motion capture means its use is not just limited to human movement research. In fact, the technology is now making strides in cognitive development research, particularly infant development research.

But why is this research so important?

The first two and a half years — and beyond — are a crucial time for both the physical and cognitive development of humans. During the first three years, we achieve important milestones and lay the foundations to our later growth and development.

For example, the human brain undergoes significant changes prenatally and continues after birth into adulthood. By studying the developmental trajectory from birth, researchers are able to understand the physiological mechanisms underlying the observed behaviour, for example, which physiological process or brain region allows us to interact with others or to walk or plan our daily activities.

This knowledge can then be applied across different situations. For example, researchers can expose babies to a particular stimuli or create certain environments that can strengthen the development of certain abilities. One area that is particularly important is the identification of atypical developmental trajectories.

Researchers can assess if a child’s developmental pattern diverges from the typical developmental curve and understand what could be preventing certain milestones from being reached. The earlier they can identify the onset of atypical behaviour, the earlier the child can have access to specialised treatment — helping to improve the developmental outcome later in life.

It’s therefore important to be able to study development at different levels, including neural, physiological and behavioural.


The limitations of lab-based studies

 Traditionally, a lot of studies in developmental research are lab-based, which typically require participants to sit in front of a computer screen watching videos, pictures or listening to sounds.

For example, eye-tracking studies have revealed how infants become more attentive to certain facial characteristics and how they process upright and inverted faces or human and non-human faces differently.

But there are currently limitations to lab-based research. For example, infants and toddlers in particular may not comply with the requirements of lab-based testing, where they are asked to stay completely still in front of a computer screen watching stimuli that are not particularly engaging after a while.

Conventional lab-based instrumentation often put restraints upon participants. For example, functional magnetic resonance imaging is not suitable for this population as they require the participant to lay completely still in a very noisy and narrow scanner, and hence can only be monitored while sleeping or under sedation.

In addition, some computer-based and lab-based functions are not always a good model of everyday life situations and can therefore lack ecological validity.

It’s therefore important that new research settings and experimental setups are available for researchers to properly study developmental population.


The importance of a natural setting

 Conducting this same research in a more natural setting can make the studies more ecologically valid. For example, an environment which infants could also encounter in preschool, in nursery or in school.

Naturalistic settings give the baby or the toddler the opportunity to move more freely with less restrictions, which means that toddlers in particular become more compliant and more willing to take part in the study.

In addition, experimental tasks can be more engaging, involving for example toys that are more interesting than passively looking at pictures on a computer screen.

More importantly, naturalistic settings give researchers the possibility to design more ecologically-valid tasks that are more similar to what we do in our everyday life. This means any tasks are a better model of real-world demands — helping to study behaviour more sensibly in more realistic scenarios.

But in order to successfully conduct this research in a natural setting, having the right technology in place is key — in particular, motion capture.


The role of motion capture

As highlighted, lab-based research typically uses eye-tracking technology to show how infants react to certain facial characteristics. But this prevents researchers from conducting studies that show a richness of behaviour that infants would also display in real life.

With wireless techniques like motion capture, researchers can now very deeply track movements alongside brain activation, while kids act more like they would at home or at school.

Motion capture can also be used to track with extremely high precision even the smallest movements that might not be clearly visible to the human eye. For example, researchers are able to use the technology to understand what strategies people use to achieve a certain target by measuring their kinematics.

The BabyLab and ToddlerLab at the Centre for Brain and Cognitive Development at Birkbeck, University of London has recently used motion capture to investigate the development of executive functions across toddlerhood, from three to five years old, in particular, action planning.

While it is known that action planning abilities evolve from three to five years old, it wasn’t clear what drove this improvement. During this particular study, children were asked to build a house with Duplo blocks while the movements of their hands were tracked using optical motion capture.

Results showed that older children have better inhibitory skills and less movement with the non-reaching hand, suggesting a greater ability to focus on executing the current tasks and less susceptibility to distraction.


Further innovation

While motion capture technology has already changed developmental research over the last few years, it’s likely we’ll see the technology become more common for these types of studies.

When studying infants’ cognitive development for example, it’s important to study the “body” as a whole and track changes at different levels, including physiological, behavioural and neural.

Our body is not separate from our brain; the body gives the brain access to the environment through movements and allows us to interact with the outside world and with other people. The brain regulates all of the functions that enable us to walk around and process the world.

The body and the brain are strongly interlinked to each other, so multimodal monitoring of infants and toddlers is key to research that aims to combine motion tracking with other monitors of brain activity, physiological changes, and behaviour.

It’s also likely motion capture technology will help across other areas of infant development, especially executive functions. For example, providing insight into how we plan actions or inhibit certain actions and how these abilities improve over time.

Another interesting area of application is social cognition, to understand for example how we collaborate with our peers and whether our actions synchronise.

These examples are only the tip of the iceberg when it comes to the many different ways in which motion capture will be used in future to transform infant development research, and I look forward to seeing what the future holds.