The book is from 1942, so is dated in thought and is linguistically frilly.
What she was getting at here, I think, is that when we think of a baby learning to speak, and it is learning the word "mama." Probably most of the time it will come to speak the word "mama" were times that before were purely emotional. That is mother has a certain emotional valence as an object and at specific times will have even more emotional significance to the baby. Langer is exploring how language takes over for those feelings and will sit on top of those f...
To finish it: "To project feelings into outer objects is the first way of symbolizing, and thus of conceiving those feelings. This activity belongs to about the earliest period of childhood that memory can recover. The conception of 'self,' which is usually thought to mark the beginning of actual memory, may possibly depend on this process of symbolically epitomizing our feelings."
"A mind to which the stern character of an armchair is more immediately apparent than its use or its position in the room, is over-sensitive to expressive forms. It grasps analogies that a riper experience would reject as absurd. It fuses sensa that practical thinking must keep apart. Yet it is just this crazy play of associations, this uncritical fusion of impressions, that exercises the powers of symbolic transformation."
Susanne Langer, Philosophy in a New Key
Do you wish to know more about human beings? Then postulate less.