The Objectives of the Research Significance of the Research

2. Brain Structure and Function

Human being has a significant organ called brain. It contains billion of neurons. The neurons are cells that process sensory information which comes in from an environment and coordinates a body to react to its environment Slepper, 2007:26. Thus, the neurons have important functions for human. The billion neurons have function to send messages rapidly into the brain and go back to the body. The major regions of the brain are medulla oblongata, the pons Varolli, cerebellum, and cerebrum. According to Steinberg 1993:175, the medulla oblongata, the pons Varolli, and cerebellum are concerned with essentially physical functions, such as breathing, heartbeat, transmission and coordination of movement, involuntary reflexes, digestion, emotional arousal, and so on. Meanwhile, cerebral cortex or cerebrum is the largest part of the human brain that functions for thinking and action. The cerebrum is divided into two hemispheres, left hemisphere and right hemisphere. Steinberg 1993: 177 says that the left hemisphere controls the right side of the body, for example the right hand, the right arm and the right side of the face while the right hemisphere controls the left side of the body. Each cerebral hemisphere is divided into four sections: frontal, parietal, temporal and occipital lobes Steinberg, 1993:182. The frontal lobe is associated with speaking, listening, reading, writing, and singing. The parietal lobe is associated with processing of sensation that will be connected with the speech and auditory area. The occipital lobe is associated with visual processing. Meanwhile, the temporal lobe is associated with comprehension of speech. A figure below shows the interiors part of the brain: Figure 1 : Brain Anatomy www. Abiireland.ie According to Sleeper 2007:29, the left hemisphere consists of two different areas: Broca‟s area and Wernicke‟s area. Broca‟s area is located in the left frontal lobe of the brain. It is associated with the production of language while Wernicke‟s area is located in the temporal lobe. It is associated with the speech comprehension.

3. Speech Production and Comprehension

Both process of speech production and speech comprehension are related to each other in language learning Steinberg, 1993:3. It means that both processes are important in producing words although speech comprehension is not always followed by speech production. When people interact with other people, they do not always produce words in their conversation. They sometimes only comprehend or think without producing words. According to Levelt in Harley 2001:374, the processes of speech production fall into three broad areas, namely conceptualisation, formulation, and encoding. The first stage is conceptualisation or message level process. This process involves human mind in conceptualising something that speaker wants to say. In the process of conceptualisation, the speakers comprehend an intention and select relevant information from memory Harley, 2001:374. The second stage is formulation process. It involves translating this conceptual representation into a linguistic form Harley, 2001:374. Thus, the formulation process happens after conceptualisation. There are two major components of formulation: lexicalisation and syntactic planning. According to Harley 2001:375, in lexicalisation, people have to select what they want to say. Meanwhile, in syntactic planning, people have to put the individual words together to form a sentence. Finally, the last process is encoding. This process involves turning words into sound. The sounds are produced in the correct sequence and specify how the muscles of the articulator system should be moved Harley, 2001:375. All processes stated above also involve the process of speech comprehension. Steinberg 1993:17 says that speech production is dependent on speech comprehension. It means that speech comprehension is important in producing language. It is an ability to understand the meaning of speech. According to Frackowiak 2004:517, the neural system for speech comprehension and production develops from cortical activity in sensory and motor areas. Since both speech comprehension and production involve the neural