Final answer:
The cerebrum is the part of the brain that controls thought, plans, and behavior, which includes processes such as reasoning, language, and memory.
Step-by-step explanation:
The area of the brain that controls thought, plans, and behavior is the cerebrum. This is the largest part of the brain and is responsible for a wide variety of functions including reasoning, language, memory, and voluntary movement. The cerebrum is composed of two hemispheres each containing four lobes: frontal, parietal, temporal, and occipital, which are connected by a structure called the corpus callosum. These lobes are associated with specific cognitive and sensory functions, such as sight and touch. Moreover, the cerebrum's outer layer, known as the cerebral cortex, is where most information processing occurs. Complex mental activities, like problem-solving and abstract thinking, as well as conscious control of our actions, are all governed by the cerebrum.