Motivation and emotion/Book/2022/Smiling and emotion

What is smiling?
Smiling can be defined as a pleasant facial expression, where it is formed to makes ones facial expression more pleasant, kind or amused. It is often viewed where the sides of the mouth are curled up and the front teeth are showing, however it is not resisted it this, but a smile most closely resembles these features. smiling is recognised cross culturally as a facial expression recognised for positive emotions such as joy, happiness, amusement and pride, however a small minority of cultures may believe smiling in public maybe inappropriate behaviour, as they believe it is associated with more negative attributions (Krys et al., 2015). smiling is just commonly linked to positive emotions, but there are many different types of smiles that can be used in different context. Some of the types of smiles can be categorized as reward, affiliative and dominance smiles, where reward smiles are intended to be intuitive, affiliative smiles are indented to make the bearer appear unthreatening and dominance smiles are presents when signifying status in social hierarchies and often viewed as lopsided sneers (Plummer, 2017). Overall, smiles are a facial expression used to convey a certain type of emotion, most commonly linked to happy emotion where a "true smile" is displayed, but can convey many other emotions through various social contents and different smile types

Facial muscles
Smiling is the result of multiple facial muscles contracting to form a smile on one’s face. Facial muscles are the muscles at lay on the cranium and can be divided into four main groups which include the muscles of the upper face, the muscles of the midface and the muscles of the lower face and neck, and the masticatory muscles. Each group of muscles consists of smaller individual muscles with the lower face and neck muscles consisting of 4 individual muscles, the midface consisting of 9 individual muscles, the upper face consisting of 4 individual muscles and the masticatory muscles consists of 4 individual muscles (Bentsianov & Blitzer, 2004. Marur et al., 2014). The muscles of the upper face make up all the muscles the lay on the forehead and eye region, while the muscles of the midface make up the muscles that are in the region below the eyes and to the bottom of the mouth and are usually the smallest muscles of the face. The masticatory muscles consist of muscle that are located on the lateral portion of the face and are deep behind the mid face muscles. The muscles of the lower face and neck are in the region below the mouth and stretch into the neck region (Bentsianov & Blitzer, 2004). The muscles of the upper, mid, and lower face are all innovated by the facial nerve, while the muscles of mastication are innovated by the trigeminal nerve via one section called the mandibular nerve (Marieb & Hoehn, 2019). The main blood supply to all these muscles is from the carotid artery which divided into multiple smaller branches with supply all the different regions and muscles (Marur et al., 2014). These muscles are used in the functions of protection to the eyes and oral competence, while also aiding in speech and the breakdown of food for digestion (Bentsianov & Blitzer, 2004).

Muscle contraction
The human body is comprised of three muscle types, smooth, cardiac, and skeletal muscles. The facial muscles fall into the skeletal muscle type as they are connected to bone. Skeletal muscles are made up of four layers. The first and largest is simply the whole muscle belly or skeletal muscle, which is made up of multiple muscle fascicles which are made up of muscles fibres which are made up of muscle fibrils. The first layer is the largest and the last layer is the smallest. Skeletal muscle can contract in three ways, concentric, eccentric, and isometric, where concentric contraction of the muscles shortens the muscle belly, eccentric contraction elongates the muscles belly and isometric contraction is contraction without movement of the muscle belly. Muscles contract firstly when nerves initiated an action potential at the neuromuscular junction creating an action potential. This action potential causes excitation-contraction coupling causing the muscle to contract. The sliding filament theory is the process in which muscles contract after being excited. Its underlying principle is the cross-bridge cycle. This how facial muscles simply contract to make smiling possible.

What muscles are activated when smiling?
The muscles which have functions in forming the facial expression around the mouth can be found in the midface region of facial muscles. These muscles are the zygomaticus minor, zygomaticus major, the Levator anguli ori. When theses muscles contrate in unisons each has a different part in forming the smile. When the zygomaticus minor contract its causes the upper lip to elevate exposing the teeth. When the zygomaticus major contracts it draws the angle of the mouth upwards, while the Levator Anguli oris muscle aids both zygomaticus major and minor in the process of smiling (Bentsianov & Blitzer, 2004). Furthermore, the orbicularis oculi muscle is also involved in smiling (Surakka & Hietanen, 1998). This muscle that is part of the upper facial muscles is a sphincter like muscles that resides around the eye. During smiling this muscle has a part to play in making the smile, it crinkles up the wears eyes to make their face more pleasant. This is what you would call a Duchenne smile where the smile barer smiles not only with their mouth but their eyes also, making the smile easily recognisable as an authentic expression of happiness (Gunnery & Ruben, 2016). Out of the many facial muscle, these are the most important facial muscles in forming a smile on ones face.

What is emotion?


Emotion is defined as “a complex reaction pattern, involving experiential, behavioural, and physiological elements, by which an individual attempts to deal with a personally significant matter or event.” By the American psychological association (APA, 2022). There are many different types of emotions that can be categorized into three categories of individual emotion. These three categories include basic (Fear, anger, disgust, contempt, sadness, joy, interest), self-conscious (shame, guilt, embarrassment, pride, triumph) and cognitively complex emotions (envy, gratitude, disappointment, regret, hope, schadenfreude, empathy, compassion) (Reeve, 2018). While some of these emotions are interrelated and alike, they all have their differences in causes, function, and perception. Emotions are useful in motivation, decision-making, understanding others and helping others understand us, while they also help us survive, thrive, and avoid danger (Cherry & Morin, 2020). Often these emotions are related to a release of certain hormones or neurotransmitters from different parts of the brain that help stimulate mood and emotion. Often imbalances in these neurotransmitters and hormones may lead to psychiatric disorders such as bipolar disorder.

It has been well research that the release of hormones and neurotransmitters can affect emotions. The brain is a complex structure with many different regions controlling specific needs of the human body such that the hypothalamus regulates eating, drinking, and sleeping while also having other functions, and the ventral tegmental area controls release of dopamine and its manufacture in the sub cortical brain. These affects of physiological needs can largely affect mood either positively or negatively. For example, if an individual is deprived of food or water, they might become irritated or angry with is a result of hyposecretion of serotonin from the. while someone that has achieved a long-term goal may feel joy when accomplishing this goal with is associated with the release of dopamine in the brain. However, it is very important that the balance of these neurotransmitters and hormones remain balanced and should not tip into either hyposecretion or hypersecretion. If there is an imbalance or fluctuation, this usually has negative effects in psychiatric disorders.

How come smiling and emotions tied?

 * When thinking of facial expressions that express joy or happiness, the most common answer will be smiling. This can be associated to the common notion that concluded that smiling is most associated with positive emotions (Krys et al., 2015).  Furthermore, it seems that across culture that this is a common trend with facial expression being commonly recognise cross-culturally (Sutherland, et al, 2018). However there seems to be a gender difference in the prevalence of smiling where Females and adolescent girls are more likely to smile, than men and adolescent boys (Lafrance, et al, 2003). Smiling is most associated with positive emotions as when the bearer smiles the brain releases the small amounts of dopamine and serotonin, which are both neurotransmitters that are associated with positive emotions (Stevenson, 2012). For this reason, most people will associate smiling with positive emotions such as happiness and joy. However, can smiling still be present even when an individual is experiencing negative emotion.

How smiling relates to different emotions
Cross, M. P., Acevedo, A. M., Leger, K. A., & Pressman, S. D. (2022)
 * How does smiling relate to sadness, anger, happiness, etc.

Positive psychology

 * what is positive psychology
 * how does this relate to smiling and emotion
 * Gable, S. L., & Haidt, J. (2005).

Therapy

 * what is available
 * how does this help improve emotion
 * Rinck, M, et al (2013)

long term

 * what are the benefits

short term

 * what are the benefits

Conclusion
Smiling and emotions are interlinked as we use the form of smiling as an facial expression which we often link to happiness and joy. Smiling releases dopamine and serotonin, both feel good neurotransmitters that allow us to feel better when we smiling thus the reason why we smile.