Newborn children eventually restrict the wide range of sounds that they make to form sounds that are similar to the one’s they hear around them in their daily environment and usually, by age 2, most children are using patterned speech, they can recognise relationships between words and situations and have also learned pragmatic skills such as taking turns in conversations, etc. This development of language skills is dependent on nature and nurture, so any deprivation during the critical period of development can cause problems with language skills.

For example, studies of blind children show initial difficulties in understanding pronouns such as “this” or “that”. This is because; those types of words are very visual and can be difficult to explain for someone without sight. However, these are initial problems and usually overcome.

On the other hand, studies of children who had been deprived of language for an extended period of time during the critical period of development show severely under developed language skills. An example is the instances of “Feral Children”, who are never spoken to during this critical period often only develop very limited language skills. http://www.feralchildren.com/en/critical.php.

Speech then is a continuous stream of sounds that can be chunked together to form words and meanings. Our perception of speech can be related to Top down Processing as we often anticipate the use of words in a speech. Sometimes, however, Speech does not work properly and one can develop Speech Slips, which can tell us about the level of processing involved in the production of speech. I think these are quite common as I have suffered from this myself and I know others who do also. I have also received numerous emails of slips made by sports commentators and even judges and lawyers which can be hilarious. The best of all though, is George W. Bush who is now notorious for them. They can be broken down as follows:

·         Substitution of word with similar meaning – indicates functional level

·         Swapping of words within a sentence – indicates positional level

·         Using incorrect word endings – indicates phonetic level

·         Spoonerisms – indicates articulation level  

So why do these speech errors happen? They are common occurrences and not as serious as Aphasia which is usually due to brain damage. I’m sure you have heard of a “Freudian Slip”. Freud believed that an error was due to the speaker thinking of more than one thing at a time and that the slip was indicative of repressed feelings or desires. While this is plausible, I think, however, that as speaking is a complex cognitive process, involving all of our cognitive abilities.

Problems with Long Term Memory Retrieval could be a cause of these errors, or the problems with Dual Task performance might also be to blame.It could also be due to Short Term Memory, if you have been thinking about something very recently and it is still stored in your STM. http://en.wikipedia.org/wiki/Freudian_slip