The correspondence in point-to-point correspondence is not necessarily between letters. If you see the word write and say “write,” for example, there are probably only two components involved. The visual wr controls the vocal “r” sound and the visual ite controls the vocal “ite” sound. The fact that there is no point-to-point correspondence between each written letter and each speech sound is a primary reason that it is difficult to read words like write and right.
A relationship between a discriminative stimulus and the response it controls with the following features:
The discriminative stimulus must have two or more components
The response must have two or more components
The first part of the stimulus must control the first part of the response, the second part of the stimulus must control the second part of the response, etc.
Formal or dynamic characteristics of the stimulus
Formal or dynamic characteristics of the response