Most of an individual's specific needs are dormant much of the time. The arousal of any particular set of needs at a specific point in time may be caused by internal stimuli found in the individual's physiological condition, emotional or cognitive processes, or by stimuli in the outside environment.
1) Physiological arousal: bodily needs at any one specific moment in time are rooted in an individual's physiological condition at that moment. A drop in blood sugar level or stomach contractions will trigger awareness of a hunger need. Secretion of sex hormones will awaken the sex need.
2) Emotional arousal: sometimes day-dreaming results in the arousal or stimulation of latent needs. People who are bored or frustrated in attempts to achieve their goals often engage in day-dreaming (autistic thinking), in which they imagine themselves in all sots of desirable situations.
3) Cognitive arousal: sometimes, random thoughts or personal achievement can lead to a cognitive awareness of needs. An advertisement that provides reminders of home might trigger instant yearning to speak with one's parents. This is the basis for many long distance telephone company campaigns that stress the low cost of international long-distance rates.
4) Environmental arousal: the set of needs activated at a particular time are often determined by specific cues in the environment. Without these cues, the needs might remain dormant. For example, the 6 o'clock news, the sight or smell of bakery goods, fast-food commercials on television, the end of the school day- all of these may arouse the "need" for food. In such cases, modification of the environment may be necessary to reduce the arousal of hunger.