• Cause and effect: The developing child must realize that his or her actions influence other people, e.g. if the child cries or lifts an arm then somebody responds.

• Reciprocity: The child must realize that communication is reciprocal, i.e. particular behaviors on the part of other people require a response from the child. For example, if the child’s mother smiles then the child should smile back.

• Symbolic understanding: The symbols used in language are words and the developing child must, therefore, learn to represent objects and things in their environment by words.

• Memory: This is the process of storing and retrieving information in the brain. It is important in learning, thinking and language acquisition. Auditory memory is particularly important, as speech is transient. What we mean by this is that when a word, or string of words, is spoken they are heard once and then the sound disappears. The sounds do not remain for us to listen to them again in order to check our understanding or otherwise revise them (unless, of course, they have been recorded for playback on a PC, Hi-fi system or similar). This is in contrast to the same word, or string of words, being written down. When they are written down, a permanent record is made of the message and it can be read and reread at leisure. Thus, the child needs to be able to store the auditory signal in the brain long enough to be able to process its meaning and respond appropriately.

• Sounds: A child must be able to make a range of different speech sounds and be able to make their voice rise and fall rhythmically.

• Hearing and listening: Children need to be able to hear and locate sounds (identify the position that they are coming from) and they must be able to attend (listen) to those that are important and ignore those that are not.

• Imitation: Children need to be able to copy a variety of speech sounds and sound patterns.

• Motivation: The child must want to communicate using speech if they are to do so successfully.

One final but important point is that a child may be physically able to produce speech sounds but may not be able to use them meaningfully unless he or she has understanding. In other words, the child must have first developed certain language skills that inform him or her how the speech sounds can be used to form meaningful words and phrases. If the sounds are only used to create random combinations then they cannot convey any substantive meaning. It is only when speech sounds are used systematically that people can be said to be capable of communicating effectively through speech.