II.

Simple Forms Of Learning

Habituation, one of the simplest types of learning, is the tendency to become familiar with a stimulus after repeated exposure to it. A common example of habituation occurs in the orienting response, in which a person’s attention is captured by a loud or sudden stimulus. For example, a person who moves to a house on a busy street may initially be distracted (an orienting response) every time a loud vehicle drives by. After living in the house for some time, however, the person will no longer be distracted by the street noise—the person becomes habituated to it and the orienting response disappears.

Despite its simplicity, habituation is a very useful type of learning. Because our environments are full of sights and sounds, we would waste a tremendous amount of time and energy if we paid attention to every stimulus each time we encountered it. Habituation allows us to ignore repetitive, unimportant stimuli. Habituation occurs in nearly all organisms, from human beings to animals with very simple nervous systems. Even some one-celled organisms will habituate to a light, sound, or chemical stimulus that is presented repeatedly.

Sensitization, another simple form of learning, is the increase that occurs in an organism’s responsiveness to stimuli following an especially intense or irritating stimulus. For example, a sea snail that receives a strong electric shock will afterward withdraw its gill more strongly than usual in response to a simple touch. Depending on the intensity and duration of the original stimulus, the period of increased responsiveness can last from several seconds to several days.