The expectation is that the student will come up with different types of errors. Semantic substitutions are pretty straightforward, as they are motivated by meaning-relations. Consequently, one need not even know the form of the participating signs in order to predict that e.g. dog could be substituted for cat. Obviously, for constructing a phonological substitution, the phonological form of the substituted and the substituting sign must be known. One would likely be substituted for the other if they differ in only one phonological parameter. In addition, the student should construct an error illustrating the anticipation, perseveration, or exchange of a phonological parameter. For illustration, we use examples from DGS.

1. develop could be replaced by bicycle. This is a case of phonological substitution, as the two signs are phonologically similar, that is, they share phonological parameters. The location and movement are the same in both signs, but the handshape and the orientation are different. This is not a semantic substitution since the concepts are not semantically related to each other.

2. In an utterance, dog could be replaced by cat; this would be a semantic substitution, as the signs come from the same semantic field, but are not phonologically similar.

3. In DGS, the possessive pronoun poss ₁ is articulated with a flat hand making contact with the chest, while the sign brother is articulated with two -hands contacting each other. In the noun phrase [poss ₁ brother] ‘my brother’, the handshapes could be exchanged.