Final answer:
An individual who has been engaging in new behavior for less than six months is in the Action stage, which involves active change and a commitment to maintaining new behavior patterns.
Step-by-step explanation:
If someone is engaging in a new behavior and has been doing so for less than six months, they are in the Action stage of change. This stage is characterized by the actual alteration of behavior and the implementation of steps toward change. This period involves considerable commitment and determination as an individual works to integrate the new behavior into their daily life in a sustainable way. The Maintenance stage follows the Action stage, where the individual continues their new behavior beyond six months and works to prevent relapse into previous habits.