Walk-ins
Have you guys ever heard of walk-ins? Let's say Joe is in his 30s, and somehow, his soul entity decides to go into a baby, and he plays host in that baby's world, if he retains everything he knows so far, that baby will be very very intelligent for most of it's life (until he or she reaches 30).
"WALK-INS" is a native-American and Hindi concept...I researched it but found that some christian perspectives see it as a satanic issue...
Here's info on walk-ins, and it's just about the same as soul switch or exchange...