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Facial expressive behaviour of a chronic low back pain population

University of British Columbia

Assessment of the subjective experience of pain represents an ongoing concern in clinical, experimental and natural settings (Melzack, 1983). Previous laboratory studies (Craig & Patrick, 1985; Patrick, Craig & Prkachin, in press) using induced pain have suggested that facial expressive behaviour may provide a useful source of information additional to that offered by self-report in assessing the pain experience. There are, however, problems associated with the use of such behaviour, these being related to the issue of the voluntary and involuntary control that individuals have over their facial behaviour. The present study attempted to extend the findings of the earlier analogue research using a clinical sample of chronic low back pain patients. Self-report of pain was also investigated as were several variables of clinical interest, i.e., duration of complaint and disability status. An attempt was made to overcome the tendency of people to attenuate their facial expressiveness in the presence of others scrutinizing the behaviour. Finally, the ability to control facial expression of pain was also investigated by requesting subjects to mask their facial expression during a painful movement and by requesting them to pose an expression of painful distress. Subjects (60 male and 60 female patients at the Shaughnessy Hospital Back Pain Clinic) underwent a standardized physiotherapy protocol of four movements designed to induce low back or hip joint pain. Half of the subjects of each sex were given a set of instructions designed to enhance their overall global expressiveness. All subjects rated their acute discomfort as well as their more chronic discomfort as experienced on a "typical" basis. Subjects' facial expressions were videotaped during the standardized protocol and subsequently scored by two independent sets of coders using the Facial Action Coding System (Ekman & Friesen, 1978b) and using a global expressiveness rating system. It was hypothesized that if the Instructional Set manipulation was successful then those subjects receiving the instructions would be rated as more globally expressive than those who did not receive instruction. It was also hypothesized that greater facial activity would be present in the posed expression of painful distress than in the genuine and masked displays. A positive, albeit modest, relationship was found to exist between facial activity and self-report. This desynchrony between behaviour and self-report is common in the literature (Fordyce et al. 1984). The manipulation to enhance the global expressiveness of the subjects was unsuccessful. Males and females differed marginally, however, in terms of judges' ratings of global expressiveness with females being rated as more expressive. This difference was also discussed in light of the absence of a sex difference on the FACS variables. Subjects were somewhat successful in deliberately attenuating their facial activity during a painful movement. It was concluded that future research should focus on further investigation of the existence of configurations of facial actions expressive of pain, any one or more of which might be-displayed, rather than pursuing the existence of a prototypical pain expression. It was suggested that a prototypic expression might be more characteristic of a posed display and further research could investigate this possibility.

Text

2010-08-06

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http://hdl.handle.net/2429/27113

Psychology

University of British Columbia

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