Textbook Notes (362,755)
Canada (158,052)
Psychology (1,086)
PSYC 221 (49)

PSYC 221 Ch13 Reasoning & Decision Making.pdf

9 Pages
Unlock Document

Queen's University
PSYC 221
Kevin G Munhall

PSYC  221  –  Reasoning  &  Decision  Making   Chapter  13   Reasoning  &  Decision  Making     Decision:  making  a  choice  between  alternatives.     Reasoning:  the  process  of  drawing  conclusions.  This  means  taking  information  and  converting  it   into  a  conclusion  that  goes  beyond  the  information.  Most  decisions  are  the  product  of  reasoning.     Deductive  reasoning:  uses  syllogisms.       Inductive  reasoning:  arriving  at  conclusions  that  are  probably  true  based  on  evidence.       Notice  that  deductive  reasoning  provides  definite  conclusions  whereas  inductive  reasoning   provides  probable  conclusions.       Deductive  Reasoning:  Syllogisms  and  Logic     Syllogism:  a  sequence  of  statements  that  offers  at  least  two  premises  plus  a  conclusion.       Here  is  an  example  of  a  syllogism  from  the  text:   Premise  1:     It  takes  a  C  average  to  graduate  from  Queen’s  University.   Premise  2:     Josie  is  graduating  from  Queen’s  University.   Conclusion:     Josie  must  have  at  least  a  C  average.     Categorical  syllogisms:  premises  and  conclusion  describe  the  relation  between  two  categories  by   using  statements  that  begin  with  all,  no,  or  some.       Here  is  an  example  of  a  categorical  syllogism:   Premise  1:     All  birds  are  animals.   Premise  2:     All  animals  eat  food.   Conclusion:   Therefore,  all  birds  eat  food.     What  determines  whether  there  is  “good  reasoning”  behind  a  syllogism?  The  answer  is:  validity   and  truth.       Validity  (of  syllogisms):  a  syllogism  is  valid  when  its  conclusion  follows  logically  from  its  two   premises.  Validity  of  the  syllogism  depends  on  the  form,  not  the  truth.  Here  is  an  example:     Premise  1:     All  birds  are  animals.   Premise  2:     All  animals  have  four  legs.   Conclusion:     All  birds  have  four  legs.     This  syllogism  is  clearly  wrong,  but  it  is  still  valid.  Why?  Because  the  conclusion  makes  sense   based  on  the  relationships  presented  in  the  premises.  This  demonstrates  how  validity  is   independent  of  truth  when  it  comes  to  syllogisms,  but  that  both  are  needed  to  make  a  correct   conclusion.   1   PSYC  221  –  Reasoning  &  Decision  Making   When  it  comes  to  syllogisms,  remember:     Validity  :  Form   as   Truth  :  Content     Just  as  a  syllogism  can  be  valid  but  not  true,  so  can  it  be  true  but  not  valid.  Here  is  an  example:   Premise  1:     All  students  are  tired.   Premise  2:   Some  tired  people  are  irritable.   Conclusion:     Some  of  the  students  are  irritable.       Just  because  some  tired  people  are  irritable,  that  does  not  mean  that  students  are  irritable  just   because  they  are  tired.  So,  while  each  of  these  statements  has  truth,  the  syllogism  as  a  whole  lacks   validity.       Conditional  syllogisms:  premises  have  the  form    if  ____  ...  then  ____.  This  type  of  syllogism  is  more   common  in  everyday  decision-­‐making.       Just  for  shorthand  reference,  categorical  syllogisms  use  A,  B,  and  C  (for  the  premises  and  the   conclusion)  and  conditional  syllogisms  use  p  (“if”)  and  q  (“then”).       The  if  premise  is  called  the  antecedent  and  the  then  premise  is  called  the  consequent.     Here  is  the  first  premise  of  a  syllogism:  if  I  study,  then  I’ll  get  a  good  grade.     • p  is  studying.  This  is  the  antecedent.   • q  is  getting  a  good  grade.  This  is  the  consequent.       Let’s  explore  (see  table)  syllogisms  that  use:   Premise  1:     If  I  study,  then  I’ll  get  a  good  grade.       Syllogism   Premise  1  &  2   Conclusion   Valid?   Affirming  the   If  I  study,  then  I’ll  get  a  good  grade.   Therefore,  I’ll  get  a  good  grade.   Yes   antecedent   I  studied.     Denying  the   If  I  study,  then  I’ll  get  a  good  grade.   Therefore,  I  didn’t  study.   Yes   consequent   I  didn’t  get  a  good  grade.     Affirming  the   If  I  study,  then  I’ll  get  a  good  grade.   Therefore,  I  studied.   No   consequent   I  got  a  good  grade.     Denying  the   If  I  study,  then  I’ll  get  a  good  grade.   Therefore,  I  didn’t  get  a  good   No   antecedent   I  didn’t  study.   grade.     I  have  bolded  the  first  column  because  they  are  bolded  as  definitions  in  the  book.  Know  these.     The  text  gives  a  really  good  tip.  If  you  can’t  figure  out  if  the  syllogism  is  valid  or  not,  replace  p  and   q  with  robin  and  bird.  Here  is  the  third  syllogism  in  the  chart  replaced  with  robin  and  bird:   Premise  1:     If  it’s  a  robin,  then  it’s  a  bird.     Premise  2:     It’s  a  bird.   Conclusion:     Therefore  it’s  a  robin.   2   PSYC  221  –  Reasoning  &  Decision  Making   The  Wason  four-­‐card  problem  is  an  example  of  a   conditional  syllogism:     If  vowel,  then  even  number.     The  cards  you  would  check  are  E  and  7.     • Checking  E  affirms  the  antecedent  –  if  vowel  (which  it  is)  then  it  will  have  an  even  number   (consequent).     • Checking  7  denies  the  consequent  –  since  7  denies  the  consequent  (it  is  an  odd  number)  the   antecedent  should  not  be  true.       Falsification  principle:  to  test  a  rule,  it  is  necessarily  to  look  for  situations  that  would  falsify  the   rule.       Look  at  the  previous  example.  If  there  was  a  vowel  on  the  back  of  7  the  rule  would  be  falsified.   However  in  the  task  only  4%  of  people  got  it  correct,  while  the  majority  said  that  the  experimenter   should  flip  4.  If  there  is  a  vowel  on  the  back  of  4  the  rule  is  supported  but  still  may  not  be  true.  If   there  is  a  vowel  on  the  back  of  4  this  provides  no  relevant  information,  as  the  rule  says  nothing   about  consonants  having  an  even  or  an  odd  number.       Another  version  of  the  Wason  four-­‐card  task  was  administered  using  a  real  world  syllogism:     If  drinking  beer,  then  over  19  years  old.     When  given  this  problem,  73%  of  the  participants   got  it  correct  (need  to  flip  beer  and  16  years)   whereas  none  got  the  abstract  task  correct.  This   shows  that  context  plays  a  huge  role  in  deductive   reasoning.     Pragmatic  reasoning  schema:  a  way  of  thinking  about  cause  and  effect  relationships  that  is   learned  as  part  of  everyday  life.   • This  is  a  reason  as  to  why  people  were  more  successful  at  the  “drinking  beer”  card  task.   Individuals  had  learned  that  alcohol  is  consumed  by  people  of  a  certain  age  and  that  minors   cannot  drink  alcohol.     Permission  schema:  if  a  person  satisfies  condition  A  then  they  can  carry  out  action  B.   • Example:  if  you  are  over  19  you  can  drink  beer.   • This  is  an  example  of  a  pragmatic  reasoning  schema  that  is  learned  with  every  bouncer  I   come  across.     Think  about  the  two  tasks  again.  The  goal  in  the  abstract  condition  is  to  see  if  the  rule  is  true.  The   goal  in  the  real  world  condition  is  to  make  sure  only  people  over  19  are  drinking.  This  activates   the  permission  schema  and  focus  is  drawn  to  a  card  that  pushes  the  boundary  of  the  schema.     3   PSYC  221  –  Reasoning  &  Decision  Making   Not  everyone  agrees  that  the  permission  schema  is  the  reason  that  the  real  world  conditions  are   more  often  solved.  See  next.     Social  exchange  theory:  people  will  behave  in  a  cooperative  way  that  is  mutually  beneficial.       How  does  social  exchange  theory  explain  anything?  It  suggests  that  we  are  evolutionarily  adapted   to  detect  cheating,  because  it  is  costly  to  us.  When  we  are  told  that  “the  rules  are  such”  the  goal  of   finding  a  cheater  (falsifying  the  rule)  becomes  more  salient.       The  social  exchange  theory  explanation  has  been  supported  by  several  Wason  four-­‐card  task   conditions.  Some  have  provided  rules  that  people  are  unfamiliar  with,  and  they  still  get  the  task   correct.  This  shows  that  they  are  not  relying  on  existing  permission  schema  per  se  but  are  aware   of  what  it  takes  to  falsify  the  rule  (by  detecting  a  cheater).     Recall  Donders’  complex  reaction  time  task?  In  this  psychologists  had  to  infer  mental  processes   from  a  behaviour.  The  Wason  card  task  poses  the  same  problem.  The  behaviours  used  to  solve  the   task  are  used  to  make  inferences  about  the  mental  processes  behind  decision-­‐making,  but  it  can   never  be  truly  clear  what  theory  is  true.       Inductive  Reasoning:  Reaching  Conclusions  from  Evidence     In  inductive  reasoning  premises  are  based  on  observations  of  specific  cases,  and  from  that  a   generalized  conclusion  is  formed.  For  example:     Observation:     All  the  crows  I’ve  seen  in  Kingston  are  black.  When  I  go  home  to  McKellar  all  of  the   crows  are  black  there,  too.   Conclusion:     It’s  a  pretty  good  bet  that  all  crows  are  black.     Validity  is  not  used  when  assessing  inductive  reasoning.  Instead  the  focus  is  on  strength  of  the   argument.  A  strong  argument  is  more  likely  to  be  true  whereas  a  weak  argument  is  less  likely  to   be  true.     Factors  that  contribute  to  the  strength  of  an  inductive  argument:   • Representativeness  of  observations:  How  well  does  the  observation  represent  all   members  of  a  category?   • Number  of  observations:  more  observations  =  more  likely  to  be  true.   • Quality  of  the  evidence:  stronger  evidence  results  in  stronger  conclusions.       In  real  life  we  use  inductive  reasoning  every  time  we  assume  what  has  happened  in  the  past  is   likely  to  be  true  again  in  the  future.  For  example,  I  assume  that  since  I  have  gotten  bad  service  at   the  Brass  every  time  that  I  will  get  bad  service  if  I  go  there  again.     Inductive  reasoning  also  allows  us  to  make  heuristics  (rules  of  thumb)  about  the  world.  We  don’t   check  each  chair  we  sit  on  for  the  load  it  can  hold  –  we  assume  that  since  chairs  have  supported  us   in  the  past  they  will  continue  to  do  so.  This  is  inductive  reasoning,  but  it  is  so  automatic  it  has   formed  into  a  heuristic  to  provide  our  brains  with  a  shortcut.     4   PSYC  221  –  Reasoning  &  Decision  Making   Availability  heuristic:  tendency  to  think  that  salient  events  are  more  common.  For  example,   because  news  of  the  event  sticks  to  the  mind  you  may  overestimate  the  number  of  cruise  ship   crashes  that  occur  in  a  year.       Illusory  correlations:  there  appears  to  be  a  correlation  between  two  events,  but  in  reality  there   is  no  correlation  or  the  correlation  is  weaker  than  it  is  assumed  to  be.  An  example  of  an  illusory   correlation  is  a  stereotype  (oversimplified  view  of  a  group  that  is  generally  negative).       Representativeness  heuristic:  the  probability  that  event  A  comes  from  class  B  can  be   determined  by  how  well  A  resembles  the  properties  of  class  B.       While  the  availability  heuristic  is  related  to  how  often  we  expect  events  to  occur  the   representativeness  heuristic  is  related  to  the  idea  that  people  often  make  judgments  based  on  how   much  one  events  resembles  another  event.       Here’s  an  example  of  a  representativeness  heuristic:   A  male,  Robert,  is  selected  at  random  from  the  United  States  population.  Robert  wears  glasses,  speaks   quietly,  and  reads  a  lot.  Is  it  more  likely  that  Robert  is  a  librarian  or  a  farmer?   • Most  people  assume  that  based  on  their  representativeness  heuristic  of  the  typical  traits  of   a  librarian  that  Robert  is  a  librarian.  They  are  failing  to  account  for  the  base  rate  of  the   population,  which  determines  that  you  are  statistically  more  likely  to  randomly  sample  a   farmer  (because  there  are  more)  than  a  librarian.       Base  rate:  relative  proportion  of  different  classes  in  the  population.       Recall  the  experiment  in  class:   • If  there  are  70  lawyers  and  30  engineers,  what  is  the  likelihood  that  person  X  with  these   qualities  is  an  engineer?  The  answer  is  always  30%  but  people  rate  it  more  likely  when   they  have  qualities  representative  of  an  engineer.     • In  the  example  with
More Less

Related notes for PSYC 221

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.