"Scalpel sister, we’re taking the brain apart"
Let’s forget about the right hemisphere for the time being and discuss where particular language abilities are located in the left hemisphere. We know this as, since Phineas’s time, a number of discoveries have been made and because people who had damage to those specific areas of brain then accordingly had also language disabilities. These areas are as follows:
Broca’s area – crucially involved in speech production
Wernicke’s area – understanding of speech
The articulate fascilus – a bundle of nerve fibres connecting Wernicke’s area and Broca’s area
The motor cortex – controls the articulatory muscles of the larynx, tongue, jaw and face
Tips and slips of the tongue
Behind the brain structure and the way our linguistic knowledge is organised within it, there are possible clues to why occasional speech production difficulties occur. We all experience them every now and then and perhaps more often after a night out. I bet you know the phenomenon when you feel like you know the word but it just won’t come to you when you want to use it. You might even have an accurate phonological outline, you might know the initial letters and how long the word is. This partial recollection you have suggests that our word-bank is partially organised on the basis of some phonological and semantic information while some items are trickier to be retrieved than others. Sometimes when you finally seem to remember the word you articulate it only just to find that you got it wrong while there are often strong similarities between the target word and the mistake. These are normally referred to as malapropisms, after Mrs Malaprop in a play by Sheridan who constantly produced near-misses for words.
A similar type of speech production difficulty is the slip-of-the-tongue, also known as Spoonerism after an Anglican clergyman, Rev. William Spooner. Most of our slips involve interchange of two initial sounds in a phrase. Sometimes this might be done for comical effect like in memorable quote by Oscar Wilde Works in the course of the drinking classes. It has been argued that slips of the tongue aren’t random and that they indicate the existence of different stages in articulation of linguistic expressions and that our brain slips first failing at organising the message in the correct order before it gets out of our mouths. Sometimes we can also experience so-called slips-of-the-ear in which we mishear a word or phrase which would analogically suggest that the brain tries to make sense of the auditory signal it receives and again, occasionally fails at it.