because he selected the blend, which satisfied the linguistic demands of these rules the best. Illegal non-words are for example instantaneously rejected. In conclusion, the rules which tell language users how to produce speech must also be part of our mental organization of language. Substitution errors, for instance, reveal parts of the organization and structure of the mental lexicon. Target: My thesis is too long. Error: My thesis is too short. In case of substitution errors both segments mostly belong to the same category, which means for example that a noun is substituted for a noun. Lexical selection errors are based on semantic relations such as synonymy, antonymy or membership of the same lexical field. For this reason the mental lexicon is structured in terms of semantic relationships. Target: George’s wife Error: George’s life Target: fashion square Error: passion square Some substitution errors which are based on phonological similarities supply evidence that the mental lexicon is also organized in terms of sound. Errors in speech are non-random. Linguists can elicit from the speech error data how speech errors are produced and which linguistic rules they adhere to. As a result, they are able to predict speech errors. Four generalizations about speech errors have been identified: Interacting elements tend to come from a similar linguistic environment, which means that initial, middle, final segments interact with one another. Elements that interact with one another tend to be phonetically or semantically similar to one another. This means that consonants exchange with consonants and vowels with vowels. Slips are consistent with the phonological rules of the language. There are consistent stress patterns in speech errors. Predominantly, both interacting segments receive major or minor stress. These four generalizations support the idea of the lexical bias effect. This effect states that our phonological speech errors generally form words rather than non-words. Baars (1975) showed evidence for this effect when he presented word pairs in rapid succession and asked participants to say both words in rapid succession back. In most of the trials, the mistakes made still formed actual words. Information obtained from performance additions An example of the information that can be obtained is the use of "um" or "uh" in a conversation. These might be meaningful words that tell different things, one of which is to hold a place in the conversation so as not to be interrupted. There seems to be a hesitant stage