INTRODUCTION

Science  finds  that  individuals  differ,  and  differ  widely,
in  any  trait  or  combination  of  traits.  They  thus  differ  in
their  fitness  for  certain  studies  in  school,  games  at  play,
and  jobs  at  work.  Industrial  practice  finds  that  a  large
fraction  of  this  variability  remains  within  a  group  willing
to  do  a  given  sort  of  work  at  a  given  wage  per  hour.
Consequently  if  there  are  ten  applicants  for  a  certain
job  there  will  commonly  be  a  large  advantage  to  the  employer ­
  who  selects  the  most  fit  rather  than  the  least  fit
of  the  ten.  Also  if  an  individual  has  the  choice  among  ten
jobs  of  equal  wage  there  will  commonly  be  a  large  advantage ­
  to  him  if  he  selects  the  job  for  which  he  is  most
fit  rather  than  the  one  for  which  he  is  least  fit.  Other
things  being  equal,  both  the  employer  and  the  employee
gain  in  proportion  as  men  work  at  a  job  for  which  they  are
more  fit  than  any  other  men  are,  and  as  each  man  is  given
the  job  for  which  he  is  better  fitted  than  for  any  other
job.  The  country  as  a  whole,  of  course,  gains  very  greatly
as  such  a  double  fit  is  approximated.
If  sufficient  ability  and  effort  are  expended  it  is  possible
to  measure  the  comparative  fitness  of  any  number  of  men
for  any  one  given  job,  or  the  comparative  fitness  of  any
one  man  for  any  number  of  different  jobs.  These  are  the
tasks  of  scientific  personnel  work,  the  former  being  the
special  work  of  the  employment  manager  and  the  latter
being  the  special  work  of  the  vocational  counsellor.
In  some  cases  a  direct  trial  at  the  job  itself  is  still  the
best  way  to  measure  fitness;  but  usually  the  scientific
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