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Week 7.pdf

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Department
Psychology
Course
PSYCH 2TT3
Professor
Reuven Dukas
Semester
Fall

Description
PNB  2XC3   Week  7   Oct.  22,  2013   EXERCISE   • How  would  extensive  use  of  GPS  affect  spatial  memory   &  hippocampus  size?   o We  must  separate  changes  due  to  evolution   &  learning.   o Hard  to  predict  evolutionary  change  in  humans  b/c  humans  (in  developed  countries)  don’t  attempt  to   maximize  fitness.   o Reducing  specific  learning   &  memory  demands  on  the  brain  would  reduce  the  neuronal  tissue  devoted  to   them  (b/c  the  brain  is  plastic).   o Most  humans  would  probably  have  a  diminished  spatial  memory   &  associated  hippocampus  regions .   • How  does  24h  access  to  unlim ited  Internet  info  affect  human  cognition?   o Prevents  development  of  critical  thinking   o Some  may  learn  &  memorize  less  b/c  info  is  readily  available .   o Others  may  learn  &  remember  more  b/c  large  amounts  of  relevant  info  are  re adily  accessible  &  required   for  expertise.   • Is  Google  making  us  stupid?   o Learning  &  memory  are  adaptations  to  situations  where  innate  behaviour  is  insufficient .   o Animal  species  have  specific  learning   &  memory  abilities,  which  are  adaptations  for  their  ecological  needs.     Associative  Learning   • The  formation  of  a  new  neuronal  representation  linking  either  a  stimulus  &  a  state  (classical  conditioning)  or  an   action  &  its  consequence  (instrumental  conditioning).   • Classical:  Food  is  delivered  independent  of  the  rat’s  behaviour .   • Instrumental:  The  rat’s  behaviour  causes  food  to  be  delivered .     Non-­‐associative  Learning   • Sensitization:  an  ↑  in  response  to  stimuli  (becoming  more  sensitive)   o i.e.  car  accident  (scared  to  drive  again)   o A  fearful  event  would  produce  fear  response  to  other   stimuli   • Habituation:  a  ↓  in  response  to  stimuli  (becoming  less  sensitive)   o i.e.  loud  noises  in  city  (eventually  ignore)   • Are  sensitization  &  habituation  really  non -­‐associative  learning?  Many  times  they  involve  associations  w/  context  &   one’s  memory.     à  If  tone  &  puff  are  more  separate  in  time,  what  would  happen?   Harder  for  the  brain  to  make  the  association  b/w   stimuli.       à  Extinction:  Association  already  made.  Experimenter  doesn ’t  deliver  air  puff  w/  tone.  Reduce  response  rate  to  tone .     Critical  Tests  for  Associative  Learning   • Not  all  changes  in  behaviour  result  from  associative  learning  (i.e.  limping  after  leg  injury ,  running  speed  in  high   school  vs.  now,  fatigue,  habituation,  sensitization… )   • We  must  verify  w/  proper  tests  that  associative  learning  rather  than  other  changes  have  occurred.     The  Best  Controls   • Same  proportions  of  CS  w/  US  &  CS  w/  no  US   • Same  number  of  disassociated  CS  &  US  presentations     Conclusion   • Associative  learning  occurs  only  when  presentat ion  of  the  CS  is  associated  w/  ↑  probability  of  the  US.   • But  learning  also  depends  on  the  nature  of  the  CS -­‐US  pairs.   • WHY?   o Animals  have  innate  predispositions  for  assoc iating  certain  stimuli  (CS)  w/  certain  states  (US).   o They  consider  their  prior  knowledge  &  current  experience  to  infer  what  relationships  are  likely  to  occur .   o Posterior  knowledge  =  some  function  of  prior  knowledge  &  new  evidence     A  ‘Proof’   • Suppose  we  test  a  random  sample  of  100  people  for  HIV .   • 5  people  are  expected  to  have  HIV   • of  the  other  95,  1%  or  ~10  people  will  also  test  +   • Out  of  the  15  +  tests,  only  5  (33 %)  +  tests  come  from  people  w/  HIV     ‘Proof’  2   • Suppose  we  test  a  sample  of  1000  high  risk  people  for  HIV   • 200  people  are  expected  to  have  HIV   • Of  the  other  800,  1%  or  ~8   people  will  also  test  +   • Out  of  the  208  +  tests,  200  (96 %)  +  tests  come  from  people  w/  HIV     Bayesian  Inference   • The  prior  probability  of  novel  food  being  the  cause  of  illness  is  much  higher  than  that  of  noise,  so  animals  are   innately  tuned  to  the  possible  association  b/w  taste  &  food-­‐poisoning.   • There  is  strong  evidence  that  the  animal  brain  employs  Bayesian -­‐like  computations  (i.e.  male  fruit  flies  choosing   whom  to  court,  learning  by  human  infants,  visual  perception  in  humans) .   • Many  problems  of  modern  life  can’t  be  solved  by  intuition .  Bayesian  computations  can  help  us  solve  complicated   problems  (i.e.  finding  a  lost  ship  in  the  ocean,  deciphering  a  secret  code,  personalized  teaching ).     Important  Conclusion   • Animals,  including  humans,  encounter   variation  in  space  &  time,  &  uncertainty.   • Animals  have  evolved  means  for  making  decisions  co
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