"chronic sufferer" is Reverend William Archibald Spooner, whose peculiar speech may be caused by a cerebral dysfunction, but there is much evidence that he invented his famous speech errors (spoonerisms). An explanation for the occurrence of speech errors comes from psychoanalysis, in the so-called Freudian slip. Sigmund Freud assumed that speech errors are the result of an intrapsychic conflict of concurrent intentions. "Virtually all speech errors [are] caused by the intrusion of repressed ideas from the unconscious into one's conscious speech output", Freud explained. In fact, his hypothesis explains only a minority of speech errors. Psycholinguistic classification There are few speech errors that clearly fall into only one category. The majority of speech errors can be interpreted in different ways and thus fall into more than one category. For this reason, percentage figures for the different kinds of speech errors may be of limited accuracy. Moreover, the study of speech errors gave rise to different terminologies and different ways of classifying speech errors. Here is a collection of the main types: Speech errors can affect different kinds of segments or linguistic units: Types Grammatical – For example, children take time to learn irregular verbs, so in English use the -ed form incorrectly. This is explored by Steven Pinker in his book Words and Rules. Mispronunciation Vocabulary – Young children make category approximations, using car for truck for example. This is known as hyponymy. Examples "particuly" (particularly) ← elision "syntaxically" (syntactically) ← vocabulary Scientific relevance Speech production is a highly complex and extremely rapid process so that research into the involved mental mechanisms is very difficult. Investigating the audible output of the speech production system is a way to understand these mental mechanisms. According to Gary S. Dell "the inner workings of a highly complex system are often revealed by the way in which the system breaks down". Therefore, speech errors are of an explanatory value with regard to the nature of language and language production. Performance errors may provide the linguist with empirical evidence for linguistic theories and serve to test hypotheses about language and speech production models. For that reason, the study of speech errors is significant for the construction of performance models and gives insight into language mechanisms. Evidence and insights Speech errors provide investigators with insights into the sequential order of language production processes. Speech errors clue investigators in on the interactivity of language production modules. The