Cognitive psychology/science tends to be the field most associated with the study of cognition or, broadly, the way people think. Cognition refers to the mental processes used to acquire knowledge and understand our environment and how we use this knowledge to produce behavior. Mental processes associated with attention, perception, categorization, memory, language, judgment and problem-solving influence the way we acquire, manipulate, store and retrieve information used for subsequent behavior. Cognition also refers to the ways in which these mental processes may operate at various depths/levels of processing and/or awareness (e.g., controlled--automatic processes, implicit--explicit memory, conscious--subconscious awareness) as well as awareness of one's own mental processes (i.e., metacognition).
Because you'll be required to read some brand of this book as a cognitive scientist: Benjafield, J. G. (2010). Cognition. Edgewood Cliffs, NJ: Prentice-Hall, Inc.