Table 1.

Description of cognitive functions targeted by CT training devices included in the systematic review.

Cognitive function	Description (and tests)
Working memory (WM)	A limited cognitive capacity that is responsible for temporarily holding information for active manipulation. Consists of visuospatial and phonological components, which are supervised by a central executive. WM underpins any functions that require storage and use of information. Digit, letter, and spatial span tasks that require information to be held during a simultaneous mental load (e.g., tone counting), also N-back, Operation Span Task.
Executive function (EF)	A multi-component construct that consists of a range of processes involved in the planning, organization, coordination, implementation, and evaluation of many non-routine activities. Plays a key role in allocating attention and higher-level functions. Wisconsin Card Sorting Test, verbal fluency test.
Inhibition	A sub-function of WM and aspect of executive function which actively suppresses irrelevant or unwanted information. Stroop test, Posner Flanker task, Go/NoGo.
Shifting/Switching	An aspect of executive function responsible for switching between multiple tasks. May be a function of WM. Wisconsin Card Sorting Test, Trail Making Test.
Divided attention	The ability to attend to and process two tasks or sources of information at the same time, e.g., two spatial locations. Requires shifting function. Multiple object tracking, dual-task paradigms.
Selective attention	The ability to attend to some stimuli while disregarding others that are irrelevant to the task at hand, for example, an individual's ability to search for a single letter among an array of distracting and irrelevant letters. Requires inhibition function. Visual search, dichotic listening.
Sustained attention	One's ability to maintain a focus of attention on one task for a sustained period of time. Sustained Attention to Response Task.
Fluid intelligence	The domain general ability to solve new problems and reason. Wechsler Adult Intelligence Scale, Raven's Progressive Matrices.
Crystalline intelligence	The ability to use learned knowledge and experience. Sentence completion, verbal classification.
Processing speed	Time taken to take in, process and respond to information. Can be domain specific, e.g., visual or verbal. Useful field of view, reaction times, Paced Auditory Serial Addition Test.
Short term memory (STM)	The temporary, limited capacity, passive store that holds information to be used in WM. Also referred to as episodic memory. Span tasks, Corsi Block Test.
Reasoning	The process of making judgments or conclusions based on logical processing. Very similar to fluid intelligence. Tower of London, Tower of Hanoi.