Emotions and Gait
The human brain responds to both internal and external stimuli, known as 'psychophysics' and the field of experimental psychology has studied such matters for a long time, going back to ancient philosophers alluding that human behaviours were influenced by our five senses. However, the complexities of our human body and the way we behave go far beyond the biological and biomechanical understanding in terms of establishing links between emotions and gait. The aim of this chapter is to give an essence of the connection in the areas of emotions and gait.
As our mind can take control of the way we think and the way we process emotions, these impact our behavioural responses. Our body systems have many other sophisticated sensory and motor mechanisms in addition to our senses of smell, vision, touch, hearing and taste, which also influence human behaviour and gait. For instance, the sense of motion or kinaesthetic sense (controlled by receptors in the muscles, tendons and joints), the sense of balance (commanded by receptors in the vestibular organs in the inner ear) and many other sensory receptors found in the circulatory and digestive systems. Additionally, the brain stem has regulatory centres to monitor basic body functions such heart rate, blood pressure and breathing. The brain stem plays an important part in regulating respiratory and cardiac functions and is highly sensitive to changes in blood chemistry and body temperature.1
On the one hand, when we perceive any internal biological and/or biomechanical stimuli, it is down to the individual's state of mind at the time to process the way the information is received by the brain. Subsequently, the way it is interpreted determines the choices that one can make at both cognitive and emotional levels prior to expressing a motor response. On the other hand, science could congruently argue that there is a strong correlation between the structural and physiological brain changes and the physical body affecting gait. For example, the pattern of gait observed in an elderly person who may be afraid of having a fall as a result of the natural ageing process, or the gait pattern observed by someone suffering from a neurological disorder.
Mental processes including emotions and thoughts can independently take control of the way individuals respond emotionally and physically to stimuli. The ability to attribute to humans a mental state, emotions and behaviours pertinent to each individual is what has been referred to as the theory of the mind.2 This theory also relates to the understanding that each individual has a set of original systems of beliefs, emotions, desires, intentions and knowledge. This view enables an understanding of everyday human behaviours, social interactions and the limitations involved in placing an objective judgement and/or making predictions about emotional responses and behaviours, which are not directly communicated from mind to mind. Our inability to communicate directly from mind to mind can introduce bias in the way we make assumptions and interpretations about others.
Basic Concepts of the Relationship between Emotions and Gait (Perception–Processing–Expression)
'Emotion' is a term commonly used and therefore it could become rather confusing when it comes to the distinction between conscious and unconscious processes.
Emotion is defined as 'A strong feeling deriving from one's circumstances, mood, or relationships with others'.3
Gait is defined as, 'manner of walking or running; bearing'.4
Emotional states are interrelated with the human gait, for example, at the time the brain registers highly challenging situations, such as danger, a set of physiological responses are put in motion involving both brain and body processes. Both unconscious and conscious responses activate a series of automatic physiological actions involving endocrine, autonomic and musculoskeletal functions. Whilst we are unaware of some mental processes, we are aware of others, and both of these impact the way we perceive, process, interpret and elicit an emotional and physical response. Feelings such as anger, elation, sadness, happiness and fear also involve our conscious perception of somatic (bodily) sensations. For example, an unpleasant bodily sensation such as 'pain' could trigger negative thinking; this could then trigger a range of emotions such as fear and anger, which in turn influences behaviours and body movement.1
Human motion reflects human behaviour and informs human activity recognition, human motion tracking and detection, along with movement analysis of the human body.5 The current understanding of human motion linking emotions and gait would benefit from further work in contributing to a more in-depth understanding. Humans can consciously or unconsciously influence the way body language and gestures are expressed. For example, someone could be observed smiling and appear very relaxed having just committed a heinous crime. In this sense, there is no congruence between this individual's emotional or mental state and the gait observed. This lack of correlation demonstrates the potential bias involved when it comes to understanding and analysing the complex relationship between emotions and gait.
The human body has a highly sophisticated and adaptive system to perform automatic body movements directly controlled by the nervous system. This refers to body movements outside our conscious control. Body movements and postural adjustments are the outcome of how our brain processes information and establishes the intricate connections between cognition (thought processing), personality, emotions and motor behaviours.6 Like a computer, our brain is constantly processing and automatically making appropriate adjustments to our behaviours and motor responses. Simultaneously, our brain is constantly processing our ability to think and reason2 and act or respond, or not.