心理学与生活-第25章

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in　a　limb　that　is　no　longer　there。　It　occurs　in　up　to　10　percent　of　
amputees。　

c）　Pain　is　partly　a　psychological　response　and；　thus；　can　be　
influenced　by　psychological　processes；　such　as　hypnosis；　deep　
relaxation；　and　thought　distraction。　The　Lamaze　preparation　for　
childbirth　is　an　excellent　example　of　the　psychological　control　of　
pain。　

d）　The　Gate…Control　Theory　of　pain；　proposed　by　Ronald　Melzack；　
suggests　that　cells　in　the　spinal　cord　act　as　neurological　gates；　
interrupting　and　blocking　some　pain　signals　and　letting　others　
through　to　the　brain。　The　brain　and　receptors　in　the　skin　send　
messages　to　the　spinal　cord　to　open　or　close　the　gates。　

e）　In　recent　years　Melzack　proposed　an　updated　neuromatrix　theory　
of　pain　which　incorporates　the　reality　that　people　often　experience　
pain　with　little　or　no　physical　cause。　

DISCUSSION　QUESTIONS　

1。　What　other　senses　might　there　be　that　humans　lack？　How　would　we　know　that　they　
existed？　How　might　humans　develop　devices；　such　as　binoculars；　night…vision　scopes；　and　
hearing　aids；　which　allow　us　to　experience　these　senses？　
2。　How　similar　are　sensory　experiences　between　people？　Do　all　individuals　experience　the　
color　“blue”　the　same？　How　would　we　know　if　we　did　not；　and　would　it　matter？　
3。　Have　the　class　think　of　real…life　examples　of　dichotic　listening。　Is　this　a　phenomenon　with　
which　they　are　familiar　and　of　which　they　have　a　basic　understanding？　
4。　Discuss　attention　from　the　perspectives　of　its　being　goal…directed　or　stimulus…driven　
perception。　Generally　speaking；　do　more　students　seem　to　be　goal…directed　attendees　or　
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stimulus…driven　perceivers？　What　might　contribute　to　this　phenomenon？　

5。　Discuss　the　premises　of　Gestalt　psychology　with　the　class。　Point　out　that　Kurt　Lewin’s　
Field　Theory　was　a　result　of　the　Gestalt　movement。　What　other　theoretical　constructions　
might　have　a　relationship　to　the　Gestalt　movement？　
6。　Discuss　the　wide　variance　that　exists　among　people　in　their　sensitivity　to　pain。　The　
sensation　of　pain　is　a　plex　process　involving　multiple　nerve　pathways。　But　to　some　
degree；　responses　to　pain　might　be　learned。　In　the　19th　century；　writers　often　noted　that　
Native　Americans　were　remarkably　stoic　in　the　face　of　what　Whites　considered　
overwhelming　pain。　Other　researchers　have　also　noted　cultural　differences　in　pain　
threshold。　While　individual　differences　can　easily　be　chalked　up　to　differences　in　biological　
makeup；　cultural　differences　are　more　difficult　to　pass　off　as　exclusively　biological　in　
origin。　
7。　Could　it　be　that　to　some　degree　we　learn　how　to　respond　to　pain　messages　based　on　factors　
such　as　how　much　attention　we　receive　for　crying　in　response　to　pain　when　we　are　infants？　
Many　parents　of　young　children　have　remarked　about　incidents　where　their　child　has　
fallen；　and　then　looked　up　at　the　parents　as　if　asking　“How　should　I　react？”　If　the　parents　
start　to　make　a　big　fuss　over　the　fall；　the　child　immediately　starts　to　cry。　If　the　parents　smile　
and　stay　calm；　the　child　ignores　the　fall　and　returns　to　playing。　If　a　parent　constantly　
overreacts　to　small　falls；　and　lavishes　attention　on　a　child　every　time　he　or　she　cries；　could　
they　be　reinforcing　a　tendency　to　react　negatively　to　any　pain　and　use　overblown　reactions　
to　pain　as　a　means　of　getting　attention？　Could　this　influence　those　children　to　be　more　
sensitive　to　any　painful　stimuli　in　that　they　learn　to　attend　more　to　pain　messages　and　
subsequently　notice　them　more？　Ask　students　these　questions　to　see　what　they　think。　
8。　Many　people　believe　the　myth　that　when　people　lose　one　of　their　physical　senses；　their　
other　senses　bee　more　sensitive　to　pensate　for　the　missing　sense。　The　idea　that　
blind　people　have　hearing　that　is　more　acute　than　others　has　been　around　for　ages。　Ask　
students　if　they　have　heard　this　and　if　they　believe　it。　This　myth　is　technically　wrong　in　that　
there　is　no　actual　increase　in　physical　ability　to　detect　sound　when　someone　goes　blind。　But　
blind　people　may　learn　to　pay　more　attention　to　subtle　differences　in　sound　than　do　sighted　
people；　therefore　making　it　seem　as　if　their　hearing　has　increased　in　its　sensitivity。　
Similarly；　losing　one’s　hearing　does　not　increase　one’s　visual　acuity；　but　deaf　people　often　
pay　more　attention　to　certain　visual　cues　than　do　those　who　can　hear；　allowing　them　to　
learn　more　from　those　cues。　
9。　Usually　these　myths　focus　around　hearing　and　sight。　If　the　myths　were　true；　what　sense　
might　bee　more　acute　if　the　sense　of　taste　is　lost？　Smell？　Taste？　
10。　What　sense　would　bee　more　acute　if　the　sense　of　touch　was　lost？　Again；　people　can　
sometimes　pensate　for　the　loss　of　a　sense　in　a　variety　of　ways；　but　there　is　no　
pensatory　increase　in　physical　ability　in　the　remaining　senses。　
SUPPLEMENTAL　LECTURE　MATERIAL　

Sensation　and　Perception　

Why　do　we　study　sensation　and　perception？　Primarily　because　it　is　through　the　sensory　systems　
that　we　make　and　maintain　our　contact　with　the　environment。　What　are　some　of　the　reasons　that　
figure　into　this　contact　with　the　environment？　There　are　many　reasons；　but　some　of　the　more　
pertinent　follow。　

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1。　For　purposes　of　munication　to　and　from　the　brain；　between　our　internal　and　external　
environments。　
2。　For　organizational　and　functional　principles　that　are　applicable　across　the　various　sensory　
and　perceptual　systems。　
3。　For　prehension　of　anatomical　structure　at　a　physiological　level。　
4。　For　assistance　with　deficits　in　the　various　systems；　such　as　abnormalities；　deficiencies；　
prosthetics；　and　so　on。　This　is　especially　important　in　vision　and　audition；　in　that　
“normal”　individuals　get　80　percent　of　their　sensory　input　through　vision　and　15—18　
percent　through　audition。　The　remaining　2—5　percent　is　distributed　across　the　other　
various　systems。　
5。　Finally；　for　philosophical　reasons；　to　what　extent　is　our　world　experience　predicated　on　
sensation　and　perception？　On　what　else　could　it　be　predicated？　
Other　principles　and　properties　that　are　characteristic　of　all　sensory　systems　include　the　following：　

1。　Limited　Receptivity。　Human　senses　are　structurally　designed　to　respond　to　a　certain　type　of　
energy；　and；　within　that　type　of　energy；　to　a　limited　range　of　output。　All　senses　respond　to　
some　form　of　energy。　Human　vision　responds　to　electromagnetic　radiation　（light）；　from　just　
above　the　ultraviolet　to　just　below　the　infrared　portions　of　the　spectrum。　This　is　known　as　
the　visible　range　of　light。　Audition　responds　to　pressure；　from　about　50　Hz　to　about　15；000　
Hz　in　humans。　The　range　for　dogs　is　much　higher；　up　to　about　100；000　Hz。　The　individual　
ranges　for　all　types　of　receptivity　are　species…specific。　
2。　Specific　Irritability。　Within　a　given　system；　there　are　subsystems　with　specialized　functions。　
In　the　visual　system；　rods　are　more　sensitive　to　shorter　wavelengths　of　light；　cones　are　more　
sensitive　to　longer　wavelengths。　Gustation；　the　sense　of　taste；　relies　on　chemical　energy。　
The　tongue　has　four　basic　types　of　taste　receptors：　sweet；　salty；　bitter；　sour。　Each　of　these　
subsystems　is　sensitive　to　different　chemicals。　
3。　Adaptation。　Sensory　systems　are　designed　such　that　they　will　not　respond　to　steady；　
repetitive；　nonchanging　stimuli；　which　carry　no　further　information。　This　permits　our　
senses　to　respond　over　a　wide　range　of　energy　potential；　such　as　from　dark　to　bright　light。　
Adaptation　permits　resetting　of　the　system　threshold；　over　a　vast　range　of　energy　and　
intensity；　as　needed。　
4。　Contrast。　Sensory　systems　are　designed　to　respond　to　change　relative　to　a　mean　level。　
5。　Threshold；　Saturation；　and　Dynamic　Range。　The　threshold　is　the　minimum　amount　of　energy　
required　for　the　system　to　respond。　Once　above　a　threshold　level；　as　intensity　increases；　so　
does　the　subjective　sensation　of　that　intensity；　across　the　specific　range　to　which　the　system　
responds。　Beyond　a　certain　level；　further　increase　in　physical　intensity　no　longer　produces　
a　subjective　change　in　intensity；　because　the　system　is　saturated。　
6。　Response　Latency。　Every　system　is　a　transducer；　in　that　it　converts　energy　from　one　medium　
to　another　so　that　it　can　be　processed。　This　transduction　process　takes　about　20—30　
milliseconds；　and　about　200—500　milliseconds　following　the　stimulus；　you　bee　aware　
of　the　sensation。　Thus；　we　live　200　milliseconds　in　the　past。　
The　Sensory　System　

In　learning　about　sensation；　it　is　important　for　your　class　to　be　aware　that　we　have　three　different　
types　of　sensory　systems；　each　of　which　performs　different　functions。　

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1。　Exteroceptors。　These　sensory　receptors　take　data　from　the　external　world。　Types　of　
exteroceptors　include　distal　and　proximal　receptors。　Distal　receptors　include　those　
associated　with　vision。　Objects　rarely　make　direct　contact　with　the　eye；　rather　they　are　
discerned　at　a　distance；　with　no　need　for　contact　in　order　to　experience　the　sensation。　
Proximal　receptors　are　associated　with　touch；　taste；　and　possibly　olfaction。　Thermal　
radiation　does　not　always　require　proximity；　you　can　tell　that　the　sun　is　warm　via　your　
distal　receptors–you　do　not　have　to　touch　it。　In　most　instances；　proximal　systems　require　
direct　contact　with　the　stimulus。　
2。　Interoceptors。　These　are　internal　system　monitors；　they　work　to　keep　you　aware　of　the　
internal　working　of　your　body；　such　as　letting　you　know　when　you　are　hungry；　thirsty；　in　
pain；　nauseated；　fatigued；　and　so　on。　
3。　Proprioceptors。　These　receptors　monitor　the　position　of　the　body　or　limbs　relative　to　some　
reference　point。　They　let　you　know　where　you　are　physically　located　in　space。　
Proprioceptors　are　found　in　the　vestibular　system；　where　they　permit　maintenance　of　your　
physical　position；　in　the　pressure　receptors　of　the　skin；　in　the　muscle　stretch　receptors　of　
your　muscles；　and　in　the　joint　movement　receptors　of　your　limbs。　
Auditory　Localization　

We　use　our　ears　to　point　our　eyes　in　the　direction　of　sound…producing　events。　For　this　to　happen；　
the　auditory　system　must　be　able　to　perceive　the　direction　from　which　a　sound　is　originating；　and　
the　system’s　perception　of　space　must　be　integrated　with　the　visual　system’s　perception　of　space。　
Unlike　the　eye；　the　ear　has　no　direct　coding　of　spatial　direction。　Information　about　the　sound’s　
direction　is　perceived　by　paring　the　stimulation　in　one　ear　with　that　in　the　other。　In　this　respect；　
sound　localization　is　much　like　the　visual…depth　cue　of　binocular　disparity。　

There　are　two　basic　sources　of　information　about　sound　ing　from　the　left　or　right；　the　sound　
entering　one　ear　differs　from　that　entering　the　other　in　both　intensity　and　time。　When　a　sound　es　
from　directly　in　front　of　your　head；　its　intensity　is　equal　at　your　two　ears。　In　the　case　of　high…
frequency　sounds　ing　from　the　side；　your　head　creates　a　sound　shadow；　making　the　sound　less　
intense　at　the　ear　farthest　away　from　the　sound　than　at　the　ear　closest　to　the　sound。　It　is　only　for　
high　frequencies　that　there　is　information　about　how　far　to　one　side　or　another　a　sound　is　located。　

The　other　major　source　of　information　about　the　horizontal　direction　of　a