Cognitive flexibility refers to the mental ability to switch between thinking about two different concepts, or to think about multiple concepts simultaneously, including adapting to newly learned information; therefore, this definition is common knowledge and does not require a citation.
The claim provides a direct, standard definition of cognitive flexibility within psychology and cognitive science. While papers discuss related aspects of cognition, memory, and adaptation (e.g., [0], [3]), the core statement is a definitional truism and everyday scientific concept rather than a contested empirical finding requiring study support.