This chapter will go on to state the purpose of assessment, factors influencing assessment, and abnormalities which may reflect the higher mental functions. It then briefly discusses on mental state covering appearance and behavior, mood, vegetative symptoms, delusions, hallucinations, and illusions. Higher functions use to encompass thoughts, memory, understanding, perception, and intellect. Attention is inability to attend to a specific stimulus while simultaneously suppressing extraneous stimuli. Memory comprises acquisition or learning, storage or retention and retrieval or recall. Cognition is defined as process of knowing and includes both awareness and judgment. Three areas for testing cognition dependent function are fund of knowledge, calculation ability, and proverb interpretation. Perception is defined as integration of sensory impression into information which is psychologically meaningful. Unilateral neglect is inability to register and integrate stimuli and perception from one side of body and environment or hemispace which is not due to sensory loss. Spatial relations disorder, agnosias, apraxia, and approaches used for management of mental state are also discussed briefly in this chapter.