Habituation and classical conditioning
Habituation and dishabituation
Habituation is the process of becoming so used to a stimulus through repeated or prolonged exposure that it fades into the background of awareness. Over time, you learn to ignore that stimulus. For example, if you spend time in a crowded bar with loud music, the noise may feel overwhelming at first. After a while, it becomes less noticeable. Then, when you step outside into the quieter sounds of a street or parking lot, the outside environment can seem surprisingly muted.
Dishabituation is the reversal of habituation. A stimulus that you had been ignoring becomes noticeable again and captures your attention. This can happen after a short or long interval. Often, it occurs when something changes in the environment - once the situation shifts, the previously “tuned out” stimulus can stand out again.
When we look at behavior, it helps to separate innate actions from learned actions.
Innate behaviors include both instincts and reflexes - responses present at birth. Reflexes are automatic motor or neural responses to specific environmental stimuli. They’re usually simple and involve particular body parts or systems (for example, the knee-jerk reflex or the pupil constricting in bright light). Reflexes are controlled by more primitive parts of the central nervous system, such as the spinal cord and medulla.
Instincts are also unlearned, but they involve broader patterns of behavior. They can be triggered by a wider range of events, including changes tied to maturation or seasonal variation. Instincts tend to be more complex and involve the whole organism, such as sexual behavior or migration, and they rely on higher brain centers.
Learned behaviors develop through experience. Learning is a relatively enduring change in behavior or knowledge that occurs as a result of experience. Unlike innate behaviors, learning involves acquiring new skills or information over time.
A major mechanism behind learning is associative learning, the tendency to connect events that occur close together in time or in a consistent sequence. Through associative learning, an organism forms links between stimuli or events that regularly occur together. This process is central to several kinds of learning, including classical conditioning.
In classical conditioning (also called Pavlovian conditioning), organisms learn to associate stimuli or events that repeatedly occur together. For example, during a storm, a flash of lightning is often followed by thunder. Over time, thunder - which naturally triggers a startle response - becomes linked with lightning. As a result, seeing lightning alone may begin to produce a similar reaction.
In Pavlov’s experiments, researchers measured dogs’ salivary responses to different stimuli. At first, meat powder naturally caused the dogs to salivate. This unlearned response is the unconditioned response (UCR), and the meat powder that produces it is the unconditioned stimulus (UCS). The dogs did not salivate to stimuli unrelated to food, such as an empty bowl or the sound of footsteps, because these were neutral stimuli (NS) before conditioning.
During conditioning, a neutral stimulus (such as a tone) was presented immediately before the unconditioned stimulus (meat powder).
After repeated pairings, the tone began to trigger salivation on its own. At that point, the tone became a conditioned stimulus (CS), and the salivation it produced became a conditioned response (CR). In other words, the dogs learned that the tone predicted food, so the tone alone was enough to produce salivation.
Furthermore, higher-order conditioning (or second-order conditioning) can happen when a new stimulus is paired with an existing conditioned stimulus. This may be done deliberately in experiments or occur naturally. For example, a pet might learn that the sound of a can opener predicts food. If the squeak of a cabinet door reliably happens just before the can opener, the cabinet squeak may also become a secondary stimulus that predicts food. Conditioning beyond second-order is generally difficult to achieve.
Discrimination and generalization
Another important part of learning is discrimination, the ability to tell stimuli apart. For example, an animal may learn to respond only to the specific tone that reliably predicts food, while ignoring other similar sounds that don’t.
In contrast, generalization happens when an organism shows the conditioned response to stimuli that resemble the conditioned stimulus. The more similar a new stimulus is to the original conditioned stimulus, the more likely the conditioned response is to occur. With additional experience, the organism may learn to respond more selectively and discriminate between stimuli once the differences become meaningful.
In summary, habituation and dishabituation help explain how attention shifts with repeated exposure and change. Innate and learned behaviors describe where behaviors come from, and associative learning - especially classical conditioning - shows how organisms connect events in their environment to guide future responses.