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(Zubieta et al., 2003). Others, who carry a mutated gene that disrupts pain circuit neuro-
transmission, may not experience pain (Cox et al., 2006). Such discoveries point the way
toward future pain medications that can mimic these genetic effects.
Pain is not merely a physical phenomenon of injured nerves sending impulses to a
definable brain or spinal cord area — like pulling on a rope to ring a bell. The brain can also
create pain, as it does in phantom limb sensations. When it lacks the normal sensory input
from a missing limb, the brain may misinterpret and amplify spontaneous but irrelevant
central nervous system activity. As the dreamer sees with eyes closed, so 7 in 10 people
who have undergone limb amputation feel pain or movement in their nonexistent limbs
(Melzack, 1992, 2005). Some may even try to lift a cup with a phantom hand, or step off a
bed onto a phantom leg. Even those born without a limb sometimes perceive sensations
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
from the absent arm or leg; the brain comes prepared to anticipate “that it will be getting
information from a body that has limbs” (Melzack, 1998).
Phantoms may haunt other senses, too. People with hearing loss often experience
Reinhold Matay/AP Photo the sound of silence. Tinnitus, the phantom sound of ringing in the ears, is not produced
repeat (the dependent variable). Copyright © Bedford, Freeman & Worth Publishers.
by vibrating air molecules but is accompanied by auditory brain activity (Sedley et al.,
2015). People who lose vision to glaucoma, cataracts, diabetes, or macular degeneration

Distracted from the pain After a may experience phantom sights — nonthreatening hallucinations (Painter et al., 2018).
Others who have nerve damage in the tasting and smelling systems have experienced
tackle in the first half of a competitive phantom tastes or smells, such as ice water that seems sickeningly sweet or fresh air that
game, Mohammed Ali Khan (here
playing for BK Häcken in white) said reeks of rotten food (Goode, 1999). The point to remember: We feel, see, hear, taste, and
he “had a bit of pain” but thought it smell with our brain.
was “just a bruise.” With his attention
focused on the game, he played on. In
the second half, he was surprised to Psychological Influences
learn that his leg was broken.
One powerful influence on our perception of pain is the attention we focus on it. Athletes,
focused on winning, may perceive pain differently and play through it. Injured soldiers,
caught up in battle, may feel little or no pain until they reach safety.
We also seem to edit our memories of pain, which often differ from the pain we actu-
ally experienced. In experiments, and after painful medical procedures or childbirth, people
®
AP Science Practice overlook a pain’s duration. Instead, their memory snapshots record two factors: their pain’s
peak moment (which can lead them to recall variable pain, with peaks, as worse [Chajut
Research et al., 2014; Stone et al., 2005]) and how much pain they felt at the end. In one experiment,
In the cold-water experiment people immersed one hand in painfully cold water for 60 seconds, and then the other hand
discussed here, researchers in the same painfully cold water for 60 seconds followed by a slightly less painful 30 seconds
manipulated the pain experienced
(the independent variable), then more (Kahneman et al., 1993). Which experience would you expect they recalled as most
measured participants’ preference painful?
for which trial they would rather
Curiously, when asked which trial they would prefer to repeat, most preferred the
Can you identify the independent 90-second trial, with more net pain — but less pain at the end. Physicians have used this
variable and dependent variable principle with patients undergoing sedation-free colon exams — lengthening the discom-
in the chocolate experiment? fort by a minute but lessening its intensity at the end (Kahneman, 1999). Imagine undergo-
You can review these important
concepts in Unit 0. ing a painful procedure and having the doctor ask if you’d rather go home now or bear a few
more minutes of milder discomfort. There’s a case to be made for prolonging a tapered hurt.
The end of an experience can color our memory of pleasures, too. In one simple exper-
iment, some people, on receiving a fifth and last piece of chocolate, were told it was their
“next” one. Others, told it was their “last” piece, liked it better and rated the whole experi-
CULTURAL ment as more enjoyable (O’Brien & Ellsworth, 2012). Endings matter.
AWARENESS
Our cultural beliefs and traditions
influence our experience of pain. Had Social-Cultural Influences
you ever thought about social-cultural Pain is a product of our attention, our expectations, and also our culture (Gatchel et al.,
influences on pain? What are some
ways your culture might play a role in 2007; Reimann et al., 2010). Not surprisingly, then, our perception of pain varies with our
your experience of pain? social situation and our cultural traditions. We tend to perceive more pain when others

146 Unit 1 Biological Bases of Behavior

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