Final answer:
The child is using substitution, a common phonological process, by replacing certain sounds with others while trying to pronounce 'Can I go?'
Step-by-step explanation:
A child who says, "Tan I dough?" for "Can I go?" is likely demonstrating the phonological process known as substitution. Substitution refers to the replacement of one speech sound with another. In this case, the child is substituting the sound /k/ in 'can' with the sound /t/ in 'tan', and the sound /g/ in 'go' with the sound /d/ in 'dough'.
In this process, the child substitutes one sound for another, which is a common occurrence in speech development. The child is substituting the 't' sound for the 'c' sound and the 'd' sound for the 'g' sound.