In the paper ‘Speaking and Misspeaking’ Dell gives evidence to the thesis that ‘slips of the tongue’ are not random. He observes that slips obey some rules which he analyses from a linguistic point of view.
Freudian approach aside, slips are ‘mistakes’ of the information process involved in the language production in the attempt of creating new sentences. Since the construction of a sentence implies different levels of representations-such as the semantic, the syntactic and the phonological one- these ‘mistakes’ in the language production, in their turn, must deal with the same linguistic levels.
This is even confirmed by the fact that the most slippable units correspond to the building blocks of the different linguistic levels.
The fact that most of the time, when one word erroneously replaces another, the target and substituting word are of the same syntactic category gives us evidence that slips obey a syntactic category rule. For example, in the case of the phrase exchange ‘I wanted to read my grandmother to the letter’ compared to the target sentence ‘I wanted to read the letter to my gandmother’ both ‘my grandmother’ and ‘the letter’ are noun phrases. It has even been hypothesized that there is a syntactic frame whose empty slots labeled for syntactic category indicate the potential structure of the sentence. The empty slots are then filled according to semantic principles.
Even if the syntactic category rule is the most important we can also notice semantic relations when we observe that in the case of noncontextual word substitutions the word replacing and the target word are connected due to meaning. For example in the sentence ‘I wanted to read the envelope to my grandmother’ replacing the target utterance ‘I wanted to read the letter to my grandmother’ ‘the letter’ and ‘the envelope’ are semantically related.
Moreover, also phonologically related word substitution errors have been noticed, for example in the case of the substitution of ‘start’ with ‘stop’ both beginning with /st/. Apparenty, though, since the sound sequence that make up words are, for the most part, stored in memory, constructing a phonological representation of a word would seem more an act of retrieval than an act of building. However, as we’ve already said, what causes the slips is the act of building new sentences in the attempt to satisfy our need of creativity. Therefore, if there are phonologically related word substitution errors the phonological representation must be an act of building a new sentence with phonemes in the same way as the syntactic representation is an act of building a new sentence with words.
In conclusion, all these patterns and rules respected by the slips show how the slips of tongue are not random but follow some criteria.