Final answer:
The external cue that might make a person hungry is when the clock indicates it is lunchtime, reflecting an environmental or societal influence rather than an internal physiological mechanism.
Step-by-step explanation:
An external cue that might make a person hungry is when the clock says that it is lunchtime. This is an example of an environmental or societal factor influencing hunger rather than an internal physiological cue. Physiological cues related to hunger include the sensation of an empty stomach and a drop in blood glucose levels, which signal the brain through various pathways to initiate feeding behavior. For example, when blood glucose levels drop, the pancreas and liver send out chemical signals to induce hunger. However, environmental cues such as seeing advertisements for food, smelling food, or realizing that it is a typical mealtime can also trigger hunger. This type of cue is related to learned behaviors and psychological conditioning.
In contrast, internal cues such as stomach rumbling, signals from the lateral hypothalamus, or blood sugar levels are not considered external cues. These cues are related to the body's physiological mechanisms that regulate hunger and satiety through complex feedback loops involving the hypothalamus, hormones, and nervous system.