This part of the monograph presents an assessment of the impact that language processing makes upon language change. The procedure will be the same as in the previous part. As before, the order of the individual sections is from phonological to higher levels. To begin with, the most basic issue will be addressed. If the germ of language change lies in the psycholinguistic principles underlying speaking and listening--if, in other words, the key to diachrony is to be found within synchrony --we should expect the patterns of language change to mirror the patterns in speakers' and listeners' spontaneous behaviour. By 'patterns' is meant not only the classificatory system that is considered appropriate to the description of the data but also the more specific characteristics that can be observed. The term 'behaviour' also requires explication. Since our interest is in the dynamics of change and since change involves the deviation from a norm, it is instructive to study deviant processing events, i.e. those outputs which do not conform to the current norm. From the production perspective, these deviations are referred to as slips of the tongue, from the perception perspective, as slips of the ear. These psycholinguistic data therefore provide the starting-point for the majority of the analyses to follow.
It has often been asserted but never convincingly demonstrated that language change originates in the inadvertent speech errors perpetrated by individual speakers. This view dates back to the last century and was voiced by Paul ( 1880), Meringer and Mayer ( 1895), von der Gabelentz ( 1891), and Eckhardt ( 1938) among others. The basic rationale is this. At any moment in time, a language possesses a system of norms (or rules) by which concrete utterances can be judged to be correct or incorrect, i.e. in conformity or non-conformity with the rules. A later stage in the evolution of a language is characterized by a different set of norms, to the effect that what used to be incorrect may have become part of the norm (or vice versa). According to this hypothesis, the change from stage 1 to stage 2 is brought about by a violation of norms at stage 1. In fact, as Cherubim ( 1980) argued, every correct utterance is a confirmation of the current set of norms while an incorrect utterance presents a challenge to these norms. Let us look at these violations in greater detail.
The major distinction drawn in the classification of slips of the tongue is that between contextually and non-contextually determined errors. In the former case