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Article  Spotlight  -­  Evolutionary  Predisposition  to  Fear  Snakes  but  Not  Spiders

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Evolutionary Predisposition to Fear Snakes but Not Spiders
Screaming  (or  hearing  someone  else  scream)  atthe  sight  of  a  spider  on  the  wall  is  an  experiencethat  is  likely  familiar  to  everyone,  whereas—atleast  for  people  living  in  urban  settings—seeing  asnake  is  quite  rare.  However,  in  lab  experiments,people  are  faster  to  detect  pictures  of  snakes
and  spiders  among  other  images  and  more
quickly  form  fear  associations  to  pictures  of  bothsnakes  and  spiders  than  to  pictures  of  guns  andknives,  despite  the  fact  that  the  latter  are  moredangerous  in  modern  environments.  Theseresults  have  led  researchers  to  suggest  that  quick  visual  detection  of  stimuli  that  could
be  harmful  is  not  learned,  but  is  rather  an  evolved  predisposition.  Consistent  with  thistheory,  non-­human  primates  reared  in  captivity  (and  therefore  never  exposed  tosnakes)  are  also  quicker  to  detect  pictures  of  snakes  than  other  pictures,  suggesting  ashared  inherited  mechanism  for  rapid  detection  of  fear-­relevant  stimuli.  However,evidence  for  a  spider  detection  advantage  in  non-­human  primates  is  mixed.  
In  a  recent  paper  published  in  the  Journal  of  Comparative  Psychology,  Kawai  andKoda  (2016)  revisited  the  possible  evolutionary  origins  of  fear-­relevant  animals  bycomparing  detection  times  for  pictures  of  snakes  and  spiders  among  pictures  of  a  non-­threatening  animal.  Three  adult  female  Japanese  monkeys  (Macaca  fuscata)
performed  a  visual  search  task  in  which  they  had  to  touch  a  target  picture  (e.g.,  snake)presented  among  distractor  pictures  (e.g.,  koalas)  in  a  nine-­picture  array.  All  threemonkeys  responded  faster  to  snakes  among  koalas  than  koalas  among  snakes.
However,  they  responded  equally  fast  to  spiders  among  koalas  and  koalas  amongspiders.  In  other  words,  there  was  a  visual  detection  advantage  for  snakes,  but  notspiders,  in  the  context  of  a  non-­threatening  animal.    
These  results  suggest  that  spiders  are  not  an  evolutionarily  relevant  threat  stimuli  innon-­human  primates.  Indeed,  only  0.1%  of  all  spider  species  are  poisonous,  andseveral  taxa  of  non-­human  primates  actually  eat  spiders.  In  contrast,  primatologists  inthe  field  frequently  encounter  venomous  snakes.  Although  it  is  possible  that  there  maybe  an  evolved  visual  sensitivity  to  spiders  in  humans  that  is  more  evolutionarily  recent
than  sensitivity  to  snakes,  several  other  lines  of  evidence  suggest  a  more  qualitative
difference  between  human  snake  and  spider  detection.  For  example,  unlike  the  robust
snake  detection  advantage,  the  detection  advantage  for  spiders  depends  on  searchcontext  (e.g.,  distractor  image  content)  and  can  be  modulated  by  whether  participants
explicitly  express  a  fear  of  spiders.  Thus,  the  visual  sensitivity  to  spiders  seen  inhumans  may  reflect  an  acquired,  learned  fear  that  affects  attention  via  top-­down
influences  rather  than  an  evolutionary  bottom-­up  perceptual  predisposition.
Share:  Kawai,  N.,  &  Koda,  H.  (2016).  Japanese  monkeys  (Macaca  fuscata)  quickly  detect
snakes  but  not  spiders:  Evolutionary  origins  of  fear-­relevant  animals.  Journal  ofComparative  Psychology,  130(3),  299-­303.  http://dx.doi.org/10.1037/com0000032  Editor:  Josep  Call,  PhDImpact  Factor:  2.494;;  27  of  129  in  Psychology  -­  Multidisciplinary
The  Journal  of  Comparative  Psychology®  publishes  original  empirical  andtheoretical  research  from  a  comparative  perspective  on  the  behavior,  cognition,perception,  and  social  relationships  of  diverse  species.  For  more  information,see:  http://on.apa.org/1FpPCCT.  
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