Kenneth M. Prkachin

The consistency of facial expressions of pain: a comparison across modalities

&NA; A number of facial actions have been found to be associated with pain. However, the consistency with which these actions occur during pain of different types has not been examined. This paper focuses on the consistency of facial expressions during pain induced by several modalities of nociceptive stimulation. Forty‐one subjects were exposed to pain induced by electric shock, cold, pressure and ischemia. Facial actions during painful and pain‐free periods were measured with the Facial Action Coding System. Four actions showed evidence of a consistent association with pain, increasing in likelihood, intensity or duration across all modalities: brow lowering, tightening and closing of the eye lids and nose wrinkling/upper lip raising. Factor analyses suggested that the facial actions reflected a general factor with a reasonably consistent pattern across modalities which could be combined into a sensitive single measure of pain expression. The findings suggest that the 4 actions identified carry the bulk of facial information about pain. They also provide evidence for the existence of a universal facial expression of pain. Implications of the findings for the measurement of pain expression are discussed.

The painful face - Pain expression recognition using active appearance models

Pain is typically assessed by patient self-report. Self-reported pain, however, is difficult to interpret and may be impaired or in some circumstances (i.e., young children and the severely ill) not even possible. To circumvent these problems behavioral scientists have identified reliable and valid facial indicators of pain. Hitherto, these methods have required manual measurement by highly skilled human observers. In this paper we explore an approach for automatically recognizing acute pain without the need for human observers. Specifically, our study was restricted to automatically detecting pain in adult patients with rotator cuff injuries. The system employed video input of the patients as they moved their affected and unaffected shoulder. Two types of ground truth were considered. Sequence-level ground truth consisted of Likert-type ratings by skilled observers. Frame-level ground truth was calculated from presence/absence and intensity of facial actions previously associated with pain. Active appearance models (AAM) were used to decouple shape and appearance in the digitized face images. Support vector machines (SVM) were compared for several representations from the AAM and of ground truth of varying granularity. We explored two questions pertinent to the construction, design and development of automatic pain detection systems. First, at what level (i.e., sequence- or frame-level) should datasets be labeled in order to obtain satisfactory automatic pain detection performance? Second, how important is it, at both levels of labeling, that we non-rigidly register the face?

The structure, reliability and validity of pain expression: evidence from patients with shoulder pain.

Abstract The present study examined psychometric properties of facial expressions of pain. A diverse sample of 129 people suffering from shoulder pain underwent a battery of active and passive range‐of‐motion tests to their affected and unaffected limbs. The same tests were repeated on a second occasion. Participants rated the maximum pain induced by each test on three self‐report scales. Facial actions were measured with the Facial Action Coding System. Several facial actions discriminated painful from non‐painful movements; however, brow‐lowering, orbit tightening, levator contraction and eye closing appeared to constitute a distinct, unitary action. An index of pain expression based on these actions demonstrated test–retest reliability and concurrent validity with self‐reports of pain. The findings support the concept of a core pain expression with desirable psychometric properties. They are also consistent with the suggestion of individual differences in pain expressiveness. Reasons for varying reports of relations between pain expression and self‐reports in previous studies are discussed.

Painful data: The UNBC-McMaster shoulder pain expression archive database

A major factor hindering the deployment of a fully functional automatic facial expression detection system is the lack of representative data. A solution to this is to narrow the context of the target application, so enough data is available to build robust models so high performance can be gained. Automatic pain detection from a patients face represents one such application. To facilitate this work, researchers at McMaster University and University of Northern British Columbia captured video of participants faces (who were suffering from shoulder pain) while they were performing a series of active and passive range-of-motion tests to their affected and unaffected limbs on two separate occasions. Each frame of this data was AU coded by certified FACS coders, and self-report and observer measures at the sequence level were taken as well. This database is called the UNBC-McMaster Shoulder Pain Expression Archive Database. To promote and facilitate research into pain and augment current datasets, we have publicly made available a portion of this database which includes: 1) 200 video sequences containing spontaneous facial expressions, 2) 48,398 FACS coded frames, 3) associated pain frame-by-frame scores and sequence-level self-report and observer measures, and 4) 66-point AAM landmarks. This paper documents this data distribution in addition to describing baseline results of our AAM/SVM system. This data will be available for distribution in March 2011.

Expressing pain: The communication and interpretation of facial pain signals

This article reviews recent theory and research on the origins, nature, and meaning of facial expressions of pain. A general model of pain expression, distinguishing experiential, encoding, and decoding processes involved in pain episodes, is proposed. Variables which are known to or may affect these processes are reviewed. Relationships between elements of the model and clinical phenomena of interest to health-care workers are discussed. The implications of findings in this area for health-care workers are examined. Areas in need of research are identified.

The Shoulder Pain and Disability Index demonstrates factor, construct and longitudinal validity

BackgroundThe Shoulder Pain and Disability Index (SPADI) is a self-report measure developed to evaluate patients with shoulder pathology. While some validation has been conducted, broader analyses are indicated. This study determined aspects of cross-sectional and longitudinal validity of the SPADI.MethodsCommunity volunteers (n = 129) who self-identified as having shoulder pain were enrolled. Patients were examined by a physical therapist using a standardized assessment process to insure that their pain was musculoskeletal in nature. This included examination of pain reported during active and passive shoulder motion as reported on a visual analogue pain scale. Patients completed the SPADI, the Coping Strategies Questionnaire (CSQ) and the Sickness Impact Profile (SIP) at a baseline assessment and again 3 and 6 months later. Factor analysis with varimax rotation was used to assess subscale structure. Expectations regarding convergent and divergent subscales of CSQ and SIP were determined a priori and analysed using Pearson correlations. Constructed hypotheses that patients with a specific diagnosis or on pain medication would demonstrate higher SPADI scores were tested. Correlations between the observed changes recorded across different instruments were used to assess longitudinal validity.ResultsThe internal consistencies of the SPADI subscales were high (α > 0.92). Factor analysis with varimax rotation indicated that the majority of items fell into 2 factors that represent pain and disability. Two difficult functional items tended to align with pain items. Higher pain and disability was correlated to passive or negative coping strategies, i.e., praying/hoping, catastrophizing on the CSQ. The correlations between subscales of the SPADI and SIP were low with divergent subscales and low to moderate with convergent subscales. Correlations, r > 0.60, were observed between the SPADI and pain reported on a VAS pain scale during active and passive movement. The two constructed validity hypotheses (on diagnosis and use of pain medications) were both supported (p < 0.01). The SPADI demonstrated significant changes over time, but these were poorly correlated to the SIP or CSQ suggesting that these scales measure different parameters.ConclusionThe SPADI is a valid measure to assess pain and disability in community-based patients reporting shoulder pain due to musculoskeletal pathology.

Reducing racial disparities in pain treatment: the role of empathy and perspective-taking.

&NA; Epidemiological evidence indicates that African Americans receive lower quality pain treatment than European Americans. However, the factors causing these disparities remain unidentified, and solutions to this problem remain elusive. Across three laboratory experiments, we examined the hypotheses that empathy is not only causing pain treatment disparities but that empathy‐inducing interventions can reduce these disparities. Undergraduates (Experiments 1 and 2) and nursing professionals (Experiment 3) watched videos of real Black and White patients’ genuine facial expressions of pain, provided pain treatment decisions, and reported their feelings of empathy for each patient. The efficacy of an empathy‐inducing, perspective‐taking intervention at reducing pain treatment disparities was also examined (Experiments 2 and 3). When instructed to attempt to provide patients with the best care, participants exhibited significant pro‐White pain treatment biases. However, participants engaged in an empathy‐inducing, perspective‐taking intervention that instructed them to imagine how patients’ pain affected patients’ lives exhibited upwards of a 55% reduction in pain treatment bias in comparison to controls. Furthermore, Pro‐White empathy biases were highly predictive of pro‐White pain treatment biases. The magnitude of the empathy bias experienced predicted the magnitude of the treatment bias exhibited. These findings suggest that empathy plays a crucial role in racial pain treatment disparities in that it appears not only to be one likely cause of pain treatment disparities but also is an important means for reducing racial disparities in pain treatment. An empathy‐inducing, perspective‐taking intervention reduced racial bias in pain treatment within experimental settings. Empathy may not only cause but can also reduce pain treatment biases.

The painful face: pain expression recognition using active appearance models

Pain is typically assessed by patient self-report. Self-reported pain, however, is difficult to interpret and may be impaired or not even possible, as in young children or the severely ill. Behavioral scientists have identified reliable and valid facial indicators of pain. Until now they required manual measurement by highly skilled observers. We developed an approach that automatically recognizes acute pain. Adult patients with rotator cuff injury were video-recorded while a physiotherapist manipulated their affected and unaffected shoulder. Skilled observers rated pain expression from the video on a 5-point Likert-type scale. From these ratings, sequences were categorized as no-pain (rating of 0), pain (rating of 3, 4, or 5), and indeterminate (rating of 1 or 2). We explored machine learning approaches for pain-no pain classification. Active Appearance Models (AAM) were used to decouple shape and appearance parameters from the digitized face images. Support vector machines (SVM) were used with several representations from the AAM. Using a leave-one-out procedure, we achieved an equal error rate of 19% (hit rate = 81%) using canonical appearance and shape features. These findings suggest the feasibility of automatic pain detection from video.

Optimism and Unrealistic Optimism have an Interacting Impact on Health-Promoting Behavior and Knowledge Changes

A general predisposition toward hopefulness (optimism) and a negation of relative risk of later health problems (unrealistic optimism) have both been thought to predict health-promoting behavior, albeit in differing directions. In Study 1 (n = 72), unrealistic optimism and optimism interacted to predict changes in exercise behavior across 6 weeks; those high on both dimensions showed the largest decrease in their reports of exercise. In Study 2 (n = 60), those high on both dimensions showed the smallest increase in their coronary heart disease (CHD) prevention knowledge after attending a CH1D prevention lecture. The results support the discriminant validity of the two optimism personality constructs while also implicating their joint importance as determinants of health-promoting behaviors.

Pain expression in patients with shoulder pathology: validity, properties and relationship to sickness impact

&NA; This study dealt with the validity and correlates of facial expressions of pain. Twenty‐four patients seeking treatment for gleno‐humeral joint pain and 12 controls underwent a standardized physiotherapy assessment protocol involving active and passive arm movements, and experimental pain induced by pressure. Subjects rated pain intensity on each trial using categorical, sensory and affective scales. Independent of testing, they completed a questionnaire measure of sickness impact. Facial behavior was measured by an abbreviated version of the Facial Action Coding System. Facial actions that related to pain indices included eyebrow lowering, narrowing and closing of the eyes, lip pulling, nose wrinkling and mouth opening. Facial actions during clinical tests showed consistent relationships with sensory and affective pain scales. Greater physical disability was associated with more intense pain actions on active, but not passive, tests. The results support the validity and generality of facial measures of pain, show that they yield graded sensitive information and suggest that they encode information about the psychosocial context of pain problems. Theoretical implications of these findings are discussed.