 What seems to be the core idea behind the specialist segregation?
He was a captain of guards in Estates-General Correctional Institution—better known to its inmates as the Jug—and if he hadn't been able to detect the scent of trouble brewing a cell-block away, he would never have survived to reach his captaincy. And, what was more important, why she couldn't adjust herself to it, now that she was in. The direction of evolution is toward specialization and Man is no exception, but with the difference that his is the one species that creates its own environment in which to specialize. From the born mechanic and the man with the gift of gab, society evolved to the point of smaller contact and less communication between the specializations, until now they could understand each other on only the most basic physical necessities—and not even always then. The ultimate should be the complete segregation of each specialization—social and genetic measures to make them breed true, because the unspecialized man is an uncivilized man, or at any rate he does not advance civilization. And letting the specializations mix would produce genetic undesirables: clerk-laborer or Professional-GI misfits, for example, being only half specialized, would be good at no specialization. And the basis of this specialization society was: "The aptitude groups are the true races of mankind." It was a perfectly good civil-service position—better than post-office clerk, not as good as Congressman, but a job you could be proud to hold. He was civil-service born and bred, and naturally he was proud and content to do a good, clean civil-service job. When you're in it, you don't much care what it is called; it is a place for punishment. Block O in Estates-General Correctional Institution was the disciplinary block, and because of the green straitjackets its inhabitants wore, it was called the Greensleeves. The two guards turned to see what was coming in as the three new candidates for the Greensleeves slumped to a stop at the head of the stairs. The outside guard pulled the switch that turned on the tanglefoot electronic fields that swamped the floor of the block corridor and of each individual cell. While the fields were on, you could ignore the prisoners—they simply could not move fast enough, against the electronic drag of the field, to do any harm. They had spent so much time in prisons that it was sometimes hard even for them to remember what they really were, outside. The inside guard finished putting the new prisoners away and turned off the tangler field once more.
 To make humanity work at it's prime, with everyone working at maximum capacity.
 To create a class system and with it a hierarchy.  To make humanity work at it's prime, with everyone working at maximum capacity.  To provide a means where people are at their happiest, working where they "should."  People are uncappable of carrying out more than one job, and the specialist segregation allows them to focus on just one.