Bardwick defines the term as "a behavioral state where a person operates in an anxiety-neutral position." Brown describes it as "Where our uncertainty, scarcity and vulnerability are minimized — where we believe we’ll have access to enough love, food, talent, time, admiration. Where we feel we have some control."
Stepping out of the comfort zone raises anxiety and generates a stress response. This results in an enhanced level of concentration and focus.
White (2009) refers to the "optimal performance zone", in which performance can be enhanced by some amount of stress. Yerkes (1907) who reported, "Anxiety improves performance until a certain optimum level of arousal has been reached. Beyond that point, performance deteriorates as higher levels of anxiety are attained." Beyond the optimum performance zone, lies the "danger zone" in which performance declines rapidly under the influence of greater anxiety.
Optimal performance management requires maximizing time in the optimum performance zone.
- Alasdair A. K. White "From Comfort Zone to Performance Management" 
- Bardwick, Judith M. (1995). Danger in the Comfort Zone: From Boardroom to Mailroom--how to Break the Entitlement Habit That's Killing American Business. AMACOM Div American Mgmt Assn. ISBN 978-0-8144-7886-8.
- Tugend, Alina (11 February 2011). "Tiptoeing Out of One’s Comfort Zone (and of Course, Back In)". Retrieved 11 December 2014.
- White, Alasdair (1 December 2009). From Comfort Zone to Performance Management: Understanding Development and Performance. White & MacLean Publishing. ISBN 978-2-930583-01-3.
- Yerkes, R & Dodson, J. - "The Dancing Mouse, A Study in Animal Behavior" 1907 "Journal of Comparative Neurology & Psychology", Number 18, pp 459–482