A key idea behind the R-W model is that a CS signals or predicts the US.
One might also say that before conditioning the subject is “surprised” by the US, but after conditioning the subject is no longer surprised, because the CS predicts the coming of the US.
(Note that the model can be described mathematically and that words like “predict”, “surprise”, and “expect” are only used to help explain the model.)
Here the workings of the model are illustrated with brief accounts of acquisition, extinction, and blocking.
The model also predicts a number of other phenomena, see main article on the model.