Determine whether facial expression is asymmetrical which might indicate that is it processed in one particular hemisphere of the brain.

Abstract

This study aimed to determine whether facial expression is asymmetrical which might indicate that is it processed in one particular hemisphere of the brain. An experiment was conducted in which the participants (338 undergraduate psychology students at UWS) were given a task to complete on facial expression and emotions. They were asked to watch 12 slides on a video projection consisting of two faces each, and were asked to note down which face they thought expressed emotions more intensely. The faces were made up of left half of a face and it’s reflection (LL composite) and right half of a face and its composite (RR composite). The data was then collected and recorded and the results showed that the left composite expressed emotions more intensely as studies by Sackeim and Gur predicted. This result implying facial expression is dominantly processed in one hemisphere (right hemisphere) of the brain.

Facial expression is defined as the ‘results from one or more motions or positions of the of the . They are closely associated with our ’ (Wikipedia, 2006). Kosslyn and Rosenberg define emotion as ‘a positive or negative reaction to a perceived or remembered object, event, or circumstance, accompanied by a subjective feeling (2004, p.390). These two terms relate closely to the research study. There has been an endless amount of research conducted on facial expression on different sides of the face.

Over the years, interest has been shown towards the different aspects of functional asymmetries in the human brain. It has been suggested that emotional processes are controlled asymmetrically by the right and left brain hemispheres. Research done into emotion based on neurological factors has also used facial expressions of emotion to help the understanding of asymmetrical dominance in emotional processes. The interest in some of the research done into facial expressions is partly due to the fact that the right and left facial muscles are stimulated differently by the two hemispheres (Kosslyn and Rosenberg, 2004).

Results from previous research done in this area have not been consistent. In studies done by Ekman, Hager and Fricsen (1981), it was found that the left side of the face tends to show more expression than the right side of the face, indicating that the right hemisphere of the brain is more dominant. Others have shown the opposite, that is the right side of the face has more intense expressions than the left side (Sirota and Schwartz, 1982). There are even findings of a differentiation between positive and negative emotions (Davidson, 1993).

A lot of physio psychologists have ...

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A lot of physio psychologists have shown interest in the role of the right hemisphere in terms of recognition, and more recently, the production of facial expression. Many different researchers are studying the face to find out “how we know how we feel”.

On the basis of these theories, this study aims to determine whether or not facial expressions are asymmetrical. In other words: are they expressed differently on one side of the face, which might indicate that it is processed in a particular hemisphere which might indicate that one hemisphere of the brain is more expressive than the other. The stimuli are presented on video projection and the participants record how many times they thought RR composite was most emotionally expressive.

The independent variable was the face slides and the dependant variable was the face the participants thought expressed more emotions. It was hypothesised that the right side of the face expressed more emotions of happiness than the left side. This study is somewhat important as hemispheric asymmetry in the control of emotional expression has implications for the role of emotional expression in communication (Sackeim and Gur, 1978).

Method

Participants

Three hundred and thirty eight undergraduate psychology students of the University of Western Sydney participated in this in-class experiment as part of their course requirement. The age and sex of the participants was not mentioned. Students were required to partake in this experiment as they had to write a lab report on the findings from their research and study.

Materials

A serious of 12 video projection slides was shown to the participants. Each slide containing two faces, which were made up of left half of a face with its reflection (LL composite), and right half of a face and its reflection (RR composite). A scoring sheet was provided for the participants to state which face, either top or bottom, expressed emotions more intensely.

Procedure

Participants were asked to sit in a comfortable viewing positing of the projection screen and were told they were participating in an experiment on facial expression. They were then told to look at the projection slides which are going to be presented shortly and write on the scoresheet which face they thought expressed emotions more intensely. They were informed that this is a forced choice, and that they cannot answer “I don’t know” or “neither”, they must decide which face they think expresses emotions more intensely. The stimuli were then presented on video projection. The LL and RR composites of the original face were presented one above the other (either top or bottom). Six faces in the slides were female, and six were male but the difference was not analysed in this study. All photos had the emotional expression of happiness, different to that of Sackeim and Gur’s study where both happiness and surprise were presented.

The gender of the person in the photo was not presented in any particular order and all the photographed subjects were right handed. The screen positions of the composites was not presented in any particular order across the trials and the faces were vertical rather than horizontal to avoid any possible problems with the gaze direction of the participants. The participants responded to each stimuli in the time allowed which was 15 seconds for each slide. The participants then wrote on the scoring sheet, which face they thought expressed emotions more intensely. Responses were scored and examined according to how many times the participants chose the RR composite as being most emotionally expressive.

Results

As predicted by Sackeim and Gur (1978), Left side composites were judged to be more emotionally intense than right side composites (M = 6.793, S = 1.494). An independent samples t-test indicated t (337) = 9.76; p < 0.001. The results are significant because the p value was less than 0.05. Therefore the results proved that the left side composites were thought to be more emotionally intense than the right side composites. The t-observed (to = 9.76) is more than t-critical (tc = 1.96), therefore participants did select significantly more RR faces than expected by chance.

Discussion

The results of the study supported the hypothesis that the left side composites of the faces showed emotion more intensely. It goes to support past research done by theorists such as Sackeim, Gur, Ekman and Friscen.

Consequently, the present results favor the right hemisphere hypothesis. This hypothesis predicted larger facial muscle activity on the left side of the face.

There are possible problems which show limitations to this study. Facial actions are not limited to spontaneous emotional expressions. Besides the posed expressions, there could be false expressions which are put on to convince others that an emotions not actually felt is being experienced (Hager and Ekam, 1983). Sackeim and Gur have used observer’s judgments to assess facial asymmetry. A problem with this is that ‘judgments are based on facial cues that express emotion, but they may not be. The face provides many cues which are irrelevant to the expression of emotion, but which observers sometimes confuse with emotional cues’ (Ekman and Hager, 1983), an example of this would be wrinkles, which are usually asymmetrical on the face and might cause the observers to think the face is showing more emotion.

With these limitations in mind, it can be said that the left side does show more intense facial expression, as the mean number of participants which chose LL composites are higher than those of RR. This implicates that the right brain hemisphere could be more dominant in controlling facial expressions.

References

Hager, J.C, Ekman, P. (1983). The Inner and Outer Meanings of Facial Expressions. Social Psychophysiology: A Sourcebook. Chapter 10. Website:

Ekman, P. Hager, J.C and Fricsen, W.V (1981). The symmetry of emotional and deliberate facial actions. Psychophysiology, 18. 101-106

Kosslyn, S.M, and Rosenberg, R.S (2004). Psychology the brain the person the world, Second Edition, U.S.A, Pearson Education

Sackeim, H. A. & Gur, R. C. (1978). Lateral asymmetry in intensity of emotional expression. Neuropsychologia, 16, 473-481.

Sirota, A.d and Schwartz, G.E (1982) Facial muscle patterning and laterization during clation and depression imagery. Journal of abnormal psychology. 91, 25-34.

Wikipedia: A Free Online Encyclopaedia. Website: http://en.wikipedia.org/wiki/Facial%5Fexpression