Biomechanics of Emotions

Imagine you're in a line waiting for your turn to go through the grocery store checkout and you suddenly see someone who is very upset. Their voice is raised, you can tell by the hand gestures that they are really angry and they storm out of the doors of the store. In this scenario, did you imagine that this person walked in a specific way as they stormed off the store?

What I'm trying to getting at is this -- our emotions are interconnected with our movements, and that walking (gait) can perhaps be an implicit indicator of emotional state. In movies, television, animation, theatre etc. the movements of a person has always been used to imply their emotions. You never see actors that hop and skip across the stage in a happy upbeat tone when reciting Hamlet's famous "To be or not to be" soliloquy where the main character contemplates suicide.

So, then that bring us to the question, what are the changes in walking associated with emotions? (It's important to be cognisant here of the difference in causality and correlation. I'm investigating the correlation or association behind emotions and walking, not necessarily the causality).

This was the main question that I aimed to answer in my MSc work. You can read the actual paper here. But in general, the emotions of sadness and excitement showed the largest deviations from the neutral emotion in the way we walk. Excitement tends to be associated with an increase the speed and pace of our walk, subjects spent less time on the ground and with less foot contact time when excited. Sadness on the other hand had opposite effects, walking was slower and subjects not only spent more time on the ground while sad but they also spent more time with both of their feet planted while in the sadness condition. Although posture was not assessed, it is shown by other researchers that posture can also affected by emotion [1] . We're more hunched over, with drooping necks and less overall movement while sad but the opposite is true when we're happy.

So what is the point of this research?

Gait, is the pattern of how we walk. Physical and neurological diseases impact the way we walk and the assessment of our walking is a large determinant of disease progression, independence/autonomy and overall health. If emotions have the capacity to change the way we walk then it implicates our gait analysis everytime we measure it. How can we be sure that a decrease in walking pace today was caused by some disease or medical intervention but not a change in emotional state? Essentially emotions may act as confounds to current clinical gait analysis and thus identifying how emotions change walking can help us better identify and be specific about how to better measure gait and the effects of medical intervention and rehabilitation.

Understanding the mechanisms and nuances of emotion and gait also can help us understand how movement is processed in the brain. Neurological diseases can impact emotion and emotional moods, does that mean their gait is also implicated? Patients with clinical depression show marked changes in their gait but they're similar to the change in gait seen in participants who were sad. How are these two related and how far can we draw the conlusions between everyday "sadness" and clinical depression?