Story, first published: Astounding Science Fiction, March 1954

In "Immigrant" ..., Earthlings voluntarily travel to an alien world for their admittance into the brotherhood. One out of a thousand Earthlings are selected by the Kimonians, an alien humanoid race with parapsychic powers, to go to their planet. The planet Kimon is a "galactic El Dorado, a never-never land, the country at the rainbow's foot". All Earthlings dream of going there and none ever wants to come back. An agent, selected to find out the secret of Kimon's attraction, is hired as a "pet" or playmate for the children of a Kimonian family.
Other Earthlings on Kimon are kept happy by such delights as large bank accounts and "live-it" television (the agent actually "visits" the Battle of Hastings). In exchange, the Earthlings are developing psi powers. The agent swallows his pride and accepts his inferiority, realizing that the Kimonians have allowed humans to emigrate to take the next step in human evolution.

Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.61-62