Abstract
Facial expressions of pain are important in assessing individuals with dementia and severe communicative limitations. Though frontal views of the face are assumed to allow for the most valid and reliable observational assessments, the impact of viewing angle is unknown. We video-recorded older adults with and without dementia using cameras capturing different observational angles (e.g., front vs. profile view) both during a physiotherapy examination designed to identify painful areas and during a baseline period. Facial responses were coded using the fine-grained Facial Action Coding System, as well as a systematic clinical observation method. Coding was conducted separately for panoramic (incorporating left, right, and front views), and a profile view of the face. Untrained observers also judged the videos in a laboratory setting. Trained coder reliability was satisfactory for both the profile and panoramic view. Untrained observer judgments from a profile view were substantially more accurate compared to the front view and accounted for more variance in differentiating non-painful from painful situations. The findings add specificity to the communications models of pain (clarifying factors influencing observers’ ability to decode pain messages). Perhaps more importantly, the findings have implications for the development of computer vision algorithms and vision technologies designed to monitor and interpret facial expressions in a pain context. That is, the performance of such automated systems is heavily influenced by how reliably these human annotations could be provided and, hence, evaluation of human observers’ reliability, from multiple angles of observation, has implications for machine learning development efforts.
Highlights
Nonverbal expressions of pain are important in all forms of pain assessment because, compared to self-report, they are less likely to be influenced by situational demand characteristics and cognitive executive mediation (e.g., Craig et al 2001; Hadjistavropoulos et al 2011)
In “Study 2”, we investigated untrained observers’ ability to differentiate baseline video segments from discomforting examination segments as well as observer judgmental accuracy for pain intensity using the panoramic versus the profile view of the face
In “Study 1”, well-validated and rigorous behavioral observation techniques were both sensitive to the presence of pain, whether the visual image was from a direct frontal angle, and presumably optimal from the point of view of availability of the full array of information available in a behavioral expression, or viewed laterally
Summary
Nonverbal expressions of pain (e.g., in response to acute and phasic pain exacerbations due to movement) are important in all forms of pain assessment because, compared to self-report, they are less likely to be influenced by situational demand characteristics and cognitive executive mediation (e.g., Craig et al 2001; Hadjistavropoulos et al 2011). The evaluation of such expressions is vital in situations where the patient has limited ability to communicate verbally due to severe cognitive impairment related to dementia (e.g., Hadjistavropoulos et al 2014; Herr et al 2011). In a clinical context, staff members often observe patients from profile views (e.g., in cases where patients are lying in a hospital bed or sitting on a chair in a common area) but the impact of different angles of observation on pain assessment is not known
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