Handbook of Psychology

Assessment 303

appraisal, and behavior. Perception involve the interpretation
of nociceptive input and identi“es the type of pain (i.e., sharp,
burning, and punishing). Appraisal involves the meaning that
is attributed to the pain and in”uences subsequent behaviors.
A person may choose to ignore the pain and continue work-
ing, walking, socializing, and engaging in previous levels of
activity or may choose to leave work, refrain from all activity,
and assume the sick role (Linton & Buer, 1995). In turn, this
interpersonal role is shaped by responses from signi“cant
others that may promote either the healthy response or the
sick role.

AN INTEGRATED, MULTIDIMENSIONAL MODEL

Based on what we have just described, we suggest an inte-
grative, multidimensional model of pain. Between the stimu-
lus of tissue injury and the subjective experience of pain is a
series of complex electrical and chemical events. Four dis-
tinct physiological processes have been identi“ed in pain:
transduction, transmission, modulation, and perception.
Transduction, or receptor, activation is the process where
one form of energy (chemical, mechanical, or thermal) is
converted into another, in this case, the electrochemical nerve
impulse in the primary afferents. Noxious stimuli lead to
electrical activity in the appropriate sensory nerve endings.
Transmission refers to the process by which coded
information is relayed to those structures of the CNS whose
activity produces the sensation of pain. The “rst stage of
transmission is the conduction of impulses in primary affer-
ents to the spinal cord. At the spinal cord, activity in the
primary afferents activates spinal neurons that relay the noci-
ceptive message to the brain. This message elicits a variety of
responses ranging from withdrawal re”exes to the subjective
perceptual events. In addition, the responses of CNS neurons
to noxious stimuli are variable because they are subject to in-
hibitory in”uences elicited by peripheral stimulation or orig-
inating within the brain itself.
Modulationrefers to the neural activity leading to control
of the nociceptive transmission pathway. The activity of this
modulatory system is one reason why people with apparently
severe injuries may deny signi“cant levels of pain.
Although we are far from understanding all the complexi-
ties of the human brain, we know that there are speci“c path-
ways in the CNS that control pain transmission, and there is
evidence that these pathways can be activated by the psycho-
logical factors described earlier.
The “nal process involved with pain is perception.Some-
how, the neural activity of the nociceptive transmission neu-
rons induces a subjective experience. How this comes about
is obscure, and it is not even clear in which brain structures

the activity occurs that produces the perceptual event. The

question remains, •How do objectively observable neural

events produce subjective experience?Ž Since pain is funda-

mentally a subjective experience, there are inherent limita-

tions to understanding it.

There are several reasons for the variability in people•s re-

sponses to nociceptive stimuli. There may be an injury to the

nociceptive transmission system or to the activity of the mod-

ulatory system that lower pain intensity. There may be abnor-

mal neural activity that may produce hypersensitivity that

can result from self-sustaining processes set in motion by an

injury but that may persist beyond the time it takes for the

original injury to heal. This self-sustaining process may even

create a situation where pain is experienced without the nox-

ious stimulus produced by an active tissue damaging process

(e.g., neuropathic pain). Finally, the psychological processes

and factors described above may affect normal pain intensity

creating unpredictable responses.

From an integrative biopsychosocial perspective, pain is

viewed as a subjective perception that results from the trans-

duction, transmission, and modulation of sensory input

“ltered through a person•s genetic composition, and prior

learning history, and modulated further by their current phys-

iological state, idiosyncratic appraisals, expectations, present

mood state, and sociocultural environment.

ASSESSMENT

To understand and appropriately treat a patient whose

primary symptom is pain begins with a comprehensive his-

tory and physical examination. Patients are usually asked to

describe the characteristics (e.g., stabbing, burning), loca-

tion, and severity of their pain. Physical examination proce-

dures and sophisticated laboratory and imaging techniques

are readily available for use in detecting organic pathology.

Although the assessment of pain may at “rst seem to be quite

an easy task, this assessment is complicated by the unique

psychological, social, and behavioral characteristics of

the person. Thus, in addition to this standard medical ap-

proach, an adequate pain assessment also requires evaluation

of the myriad psychosocial and behavioral factors that in”u-

ence the subjective report.

Quantifying the Pain Severity

The response to the apparently simple question of •How

much does it hurt?Ž is more complex than it may at “rst ap-

pear. Pain resides within an individual and there is currently

no pain thermometer that provides an objective quanti“cation

of the amount or severity of pain experienced by a person.