Last updated: Sun, Jul 28, 2024
Because pain is a private experience (often labeled "subjective") there are limitations in how pain can be measured. This statement applies to pain intensity, but equally to other important aspects of pain, and to the "co-morbidities" that play such an important role in pain suffering. This inability to measure also limits what can be understood scientifically about pain. This section describes these limitations and how various types of researchers have tried to compensate for this weakness in our understanding.
Now that you know all that there is to know about scientific method and pain research in general, I'd like you to switch to scientific techniques related specifically to the study of pain. This section is a brief catalog of the methods that are available to researchers as they explore the nature of pain. Looking through the catalog should give you an idea of what is known and knowable about pain, and about the limitations and challenges that pain researchers face. Notice what is and isn't asked about.
In their chapter on self-report measures in the Pain Assessment Handbook, researchers Mark P. Jensen and Paul Karoly define pain intensity: Pain intensity may be defined as how much a person hurts.
1 I think that I may know what they mean by this, but I'm not at all sure that I do. The part of me that knows what this means, I suspect, is the part of me that knows that some pains are worse than others. The part of me that doesn't know what this means wonders how I distinguish the intensity of pain from other aspects of it. And if I think about it, I wonder whether a pain that lasts longer but is otherwise the same is more intense? Certainly it hurts more. If I think more carefully, I recall the importance of clarity and operational definitions in science (Scientific Understanding).
I imagine that the two authors know that this isn't much in the way of a definition. If you measure pain intensity level by asking people the VAS question ("What's your pain level from 0 to 10?", see Pain Intensity), then your definition of pain intensity is something like this: Pain intensity level is the number that people give us when we ask the VAS question.
This means, among other things, that pain intensity is whatever the person answering the question thinks it is. Pain intensity as reported in the results of experiments is almost always an average of VAS scores.
Nevertheless, pain intensity level, whether measured with the common VAS or by other self-report measures, is fairly consistent in those contexts in which this can be measured, whether or not anyone knows exactly what it means.
Jensen and Karoly contrast pain intensity to pain affect: Pain affect is the degree of emotional arousal or the changes in action readiness caused by the sensory experience of pain.
This definition is a good complement to their definition of intensity, in that it seems to designate something different from intensity. If there is a practical way to measure emotional arousal or action readiness, this is a plausible operational definition of pain affect. On the other hand, I am less clear as to what "the sensory experience of pain" is. Is it different from "the experience of pain" or just "pain?" The authors add that
Pain affect is, thus, a mental state triggered by an implicit or explicit appraisal of threat.
2 Here the authors seemingly have left the realm of definition and entered the realm of explanation by tying the concept of pain affect to theories about pain that are certainly challengeable.
I make these points, once again, not to disparage the work of these or other pain researchers, but to make a different point based on the nature of these definitions. These definitions suggest to me that the ideas of pain intensity and pain affect still have much of mystery about them. Just as mass and energy were not settled concepts in the past, pain intensity and pain affect aren't, and shouldn't be, settled concepts today. Researchers, doctors, and patients are caught between the need to have concepts to think and talk with and the need to be clear about what is known and what is speculative, what is settled and what is supposed.
Since pain is a "subjective" experience it isn't directly observable. Self-report isn't an ideal way of measuring for scientific or medical purposes, but it may be the best way available. And in a sense the subjective impact of pain is the most important thing about it to the patient. This section describes measures of pain, self-report and otherwise, that are used in research and medical practice. None of these measures is very good, and this taints the science of pain.
Within this section...
Pain Intensity (Last updated: Sun, Jul 28, 2024)
Pain Thresholds (This page is incomplete.)
Reported Pain in General (This page is incomplete.)
Assessing Pain Quality (Last updated: Fri, Jun 30, 2017)
Facial Expressions (Last updated: Fri, Jun 30, 2017)
Physiological Correlates of Pain (Last updated: Fri, Jun 30, 2017)
Neuroimaging and Pain Measurement (Last updated: Tue, Jan 14, 2025)
Biochemical Assays (Last updated: Mon, Jan 13, 2025)
Pain Behaviors (Last updated: Sun, Jul 28, 2024)
Psychosocial Measures (Last updated: Sat, Aug 24, 2024)
Functional Testing (Last updated: Fri, Feb 7, 2025)
Pain Measurement Illusions (Last updated: Sun, Jul 28, 2024)
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Pain Research (Last updated: Fri, Feb 21, 2025)