Blue is symbolic of loyalty, vigilance, perseverance, and truth. These cultivated an atmosphere of perpetual vigilance and suspicion within the movement. Methylphenidate is considered effective in increasing wakefulness, vigilance, and performance. Neurologically, carbon monoxide exposure reduces hand to eye coordination, vigilance, and continuous performance. Charmalaine preaches vigilance and attention to one's environment. These represent valor, purity, vigilance, and justice. A special case of collective vigilance in groups is that of sentinels. Thus, although individual vigilance decreases, the overall vigilance of the group increases. In one theory, anxiety susceptibility may increase as a result of present vigilance. It has also been proposed that the neck serves to give the animal greater vigilance. The coup was planned for the Festival of Eid, in anticipation of relaxed military vigilance. Schooling is sometimes an antipredator adaptation, offering improved vigilance against predators. The modern West generally associates owls with wisdom and vigilance. There remains historical controversy about the vigilance movements. Females may choose mates who invest more time in infant care and predator vigilance.