There have been several advances in pain assessment strategies that allow for the
measurement of graded pain levels that lie between pain threshold and pain toler-
ance and, also, provide measurement of dimensions of pain experience, namely
pain intensity and pain unpleasantness. An initial approach was the independent
development of separate lists of words describing levels of pain intensity (e.g.,
“faint,”“mild,”“moderate,”“strong,”and“extremely intense”) and pain unpleas-
antness (e.g.,“slightly unpleasant,”“annoying,”“distressing,”“slightly intolera-
ble,”and“intolerable”). Subjects then rated the relative magnitudes of pain intensity
(or pain unpleasantness) connoted by each of the words using a cross-modality
matching rating procedure, a method that provides ratio scale measures (Gracely
et al. 1978 ). So, each of the weightings for the words from each of the two lists
indicated the relative pain intensity (or pain unpleasantness) described by each
word. Subjects then selected a word from the pain intensity list to describe the pain
intensity level associated with each presentation of noxious electrical shock
delivered to the skin (seven stimulus intensity levels between threshold and toler-
ance). Each chosen word was then replaced by the previously determined word
weighting values. The resultant pain ratings were then plotted as functions of each
of the experimental pain stimulus levels. Figure6.1 provides a composite repre-
sentation of results from studies where subjects rated the pain intensity of experi-
mental pain stimuli using the quantified pain intensity verbal descriptors. The
highly correlated resultant stimulus–response functions demonstrated that subjects
could reliably rate the graded levels of experimental pain using the quantified
sensory intensity words (Heft et al. 1980 , 1984). A parallel experiment using the
pain unpleasantness words provided similar evidence that subjects could reliably
rate the pain unpleasantness of graded experimental pain. Pain patients can also use
Fig. 6.1 Verbal descriptor rating of experimental pain. The group-mean pain intensity verbal
descriptor ratings for each of the seven experimental pain stimuli plotted as functions of the
stimulus magnitudes (representation from multiple studies employing multiple stimulus types).
Each pointrepresents the mean from multiple trials
6 The Challenge of Measuring Pain in Humans 107