Communication is integral to human life. During the communication process, an idea or concept is received by an individual either from another individual or from the physical environment. Person-to-person transmission of ideas could be through the medium of spoken/written language or through non-verbal media such as body language, gesture or facial expression. Ideas or concepts communicated from the physical environment allow the individual to function within that environment. For example, the concept of traffic must be understood, so as to allow safe and effective day-to-day functioning, whilst comprehension of the concept of a CD player could allow the individual to acquire appropriate auditory stimulation for relaxation and enjoyment.