Ivan Pavlov did experiments in psychology. He was part of a group called "Behaviorists" who believe that behavior is just about stimulus and response. He did work with dogs where he "taught" them to salivate by getting them to associate the ringing of a bell to getting fed. He rang the bell before feeding them so often that they began to salivate just at the bell. He'd taught their bodies to react in a particular way.
The children in this "nursery" are being trained the same way. The government is training them to like or dislike certain conditions, not based on what they truly want or need or enjoy, but based on how the government wants them to react.
There's also a really nasty implication here because the infants are being trained like dogs, implying that have no more value than a dog. Of course, humans are devalued across the board, the one more case of devaluing human life is not particularly surprising.