THE  SCOPE  OF  PSYCHOLOGICAL  TESTS  I93
an  actual  trial.  The  psychologist  who  presumes  to  apply
tests  to  kinds  of  work  which  he  understands  only  superficially ­
  to  groups  of  men  whose  work  is  alike  only  in
superficial  details,  and  in  cases  where  the  reliability  of  the
results  rests  not  upon  an  impersonal  record  of  actual  work
but  upon  a  concoction  of  personal  opinions,  is  indeed
taking  a  very  grave  risk  of  bringing  his  medium  into  disrepute ­
  among  those  whose  business  it  is  to  be  familiar
■with  the  complexities  and  intricacies  of  employment  work.
No  doubt  all  of  these  faults  have  occurred  in  the  experiments ­
  described  here;  but  they  are  recognized  as  weaknesses ­
  and  the  results  discounted  accordingly.
The  virtue  of  the  psychological  method  consists  in
a pplying  to  the  abilities  of  people  certain  scientifically
accurate  tests,  tests  whose  value  has  first  been  determined ­
  by  means  of  experiments  which  meet  the  conditions
described.  The  superiority  of  such  measures  over  the
ordinary  haphazard  measures  of  common  sense  is  obvious. ­
  However,  this  very  virtue  is  also  the  weakness  of
the  psychological  method  or,  in  fact,  of  any  scientific
method.  Tests  and  measures  are  only  significant  when
applied  to  cases  which  conform  to  standard  conditions.
The  diagnostic  tests  applied  by  the  physician,  for  instance,
e nable  him  to  determine  the  nature  of  an  illness  like
measles  which,  because  of  its  invariable  symptoms,  we
may  call  standard.  However,  as  soon  as  an  extraordinary
dlness  occurs,  his  tests  become  useless.  They  do  not
enable  him  to  diagnose  the  nature  of  the  disease,  and  it
becomes  necessary  to  call  in  specialists  who,  in  many  cases,
are  also  unable  to  determine  the  exact  nature  of  the
trouble.  The  more  complicated  and  exceptional  the  disease,
the  less  applicable  are  the  ordinary  laws  and  measures
°f  the  physician.  Exactly  the  same  condition  prevails  in