Running Head: Asymmetry and emotional expression
Hemispheric asymmetry and emotional expression: Which side of the brain is happier?
Word Count: 1,458
Abstract An experiment was conducted among university students to determine whether a particular side of the human face (and its corresponding lateral brain hemisphere) depicted a certain emotion more intensely than the other. The 396 University students were instructed to view a video containing 12 slides with 2 human faces depicted on each. The faces were placed over each other so that the participant could clearly see any distinctions between expression. The images were of composite faces, a left side face and its reflection as well as a right side face and its reflection. Otherwise known as LL and RR composites, respectively. The participants then decided which one of the two faces expressed the emotion of happiness more intensely. Results were then recorded. The results indicated the majority of participants considered the RR composite exhibited the emotion of happiness more intensely. Although this may be the case when considering the emotion of happiness, further research is needed to determine how and why positive and negative emotions are separated within the hemispheres of the brain.
To accurately perceive emotion on another human being is a useful social tool for the perceiver. It allows better interaction as well as the ability to identify other people’s emotional states (Oosterof And Todorov, 2009). Observations and various experimental evidence has revealed that the human face is not always symmetrical, especially when displaying emotion (Borod, Yecker, Santschi and Schmidt, 1998). Thus, it is important to note that along with these facial asymmetries, there exist brain asymmetries which indicate particular types of emotion are more prevalent and intense on certain sides of the face (Alves, Aznar-Casanova and Fukusima, 2008). Cross-cultural data has indicated that happiness is an emotion which can be recognised universally, regardless of sex, age or sociological background (Sakeim and Gur, 1978).
Some studies have shown that expression of emotion is more intense in the right hemisphere of the brain, showing more on the left side of the face. This is true for almost all negative emotions which include fear and anger (Borod et. al., 1998). The interesting side of these studies show that positive emotions such as happiness are more prevalent in the left hemisphere of the brain, thus showing more intensely on the right side of the face (Sakeim and Gur, 1978). According to Davidson and Fox (1982) symmetrical activity located over the frontal cortex has been implicated in the expressions of human emotions. Explanations of this research have thus suggested that left frontal activity is associated with positive affect and more intense expressions of emotion.
In such studies where asymmetries of the face are focal, to more easily clarify hemispherical activity, the face is split into two. This split is right through the middle of the face which is then paired with its mirror image, creating a composite face (Sakeim and Gur, 1978). These composites, known as left-left (LL) composites and right-right (RR) composites have been shown to produce the most accurate and reliable judgement of emotion as the emotion depicted is more concentrated on the face as it is doubled within the composite (Sakeim and Gur, 1978).
The present study aimed to investigate whether or not participants would recognise a particular emotion on a depicted composite face. The design for the experiment was based on a study by Sakeim and Gur (1978) which tried to recognise positive and negative emotions, such as anger, surprise as well as happiness on composite faces. The study...
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positive and negative facial expressions ',Laterality: Asymmetries of Body, Brain and Cognition,14:3,256 — 272
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