Oh man, how do I do this again?
As in "emotional range of a teaspoon," to quote Hermione Granger....
Oh dang. I don't know how to write. Not like this, anyway. Perhaps a fictional approach:
Model 062390, Class A was not always Model 062390, Class A. Sometimes it was just Otto. Or, more appropriately, sometimes Otto was just Model 062390, Class A. Every once in a while his eyeballs would roll upward and he'd discover that good old Class A metal plating encasing his head, or he'd look down and it would be wrapped around his chest. And then there was the wretched insert. Sensors fed from the plating, a la acupuncture, into his spinal column where they gracefully wound upward to the insert. The insert would then interpret the input from the sensors accordingly.
Now don't misunderstand, the insert did not control Otto's brain, by any means. But it sure could raise a racket. Otto wasn't personally inclined to take its advice, but that inclination, practically speaking, meant very little when he wasn't able to tell if the voice he was hearing was it or Daddy. It was very adept at impersonating Daddy. Otto would have dearly liked to somehow reached into his own skull and yanked the thing out. But things don't work that way, obviously.
One of many tricks the insert had up its sleeve was convincing Otto that he was not, in fact, Otto but rather Model 062390, Type A. It could do this very efficiently by snaking a mechanical tendril into his chest and restricting the movement of his heart.
Otto knew the heart wasn't everything, by any means. That was one thing Daddy always reminded him of, and he knew (but didn't always feel) it to be true. But to feel the heart thump in his chest was very reassuring, and when that didn't happen (or at least happened in a stunted fashion) he, well, felt less like Otto and more like
Model 062390, Type A.