Many commentators have offered explanations for the controversy and confusion. The line between a poor performer and a person with a mental disability in need of accommodation is a difficult one to discern. Moreover, in contrast to individuals protected under other fair employment statutes, those with mental disabilities may move in and out of protected status. The EEOC Compliance Manual suggests that an "impairment" is "substantially limiting" if it lasts for more than several months and significantly restricts the performance of one or more life activities during that time. "Working" is cited in the regulations as a "major life activity"; other examples include thinking, breathing, concentrating, interacting with others, caring for oneself, speaking, walking, performing manual tasks, and sleeping.