Conditioned Reflex & Pavlov's Experiment

Conditioned Reflex

Animals can learn new ways to respond to things through experience. This type of response is called a "l Conditioned Reflex ." It means they react to certain things automatically, without thinking.

 

Pavlov's Experiment

A conditioned reflex, or learned response,  is different from an unconditioned reflex, which is an automatic response to a stimulus. The concept of conditioned reflex was introduced by the Russian physiologist Ivan Pavlov around 1900. Initially, it was called a "psychic reflex."

 

A conditioned reflex occurs when an animal learns to associate a new stimulus with a response, even though there is no natural connection between them. For example, if a person sees something sour, they might start to salivate. The actual act of putting something sour in the mouth and salivating is a natural, unconditioned reflex. However, if someone just sees something sour and starts to salivate, this is a conditioned reflex.

 

This happens because seeing the sour thing and the act of salivating are not naturally connected; it is learned. For conditioned reflexes to happen, animals need to have the ability to learn, and this involves the brain's cortex. This is why conditioned reflexes are mostly seen in mammals and other animals with well-developed central nervous systems. However, recent studies have shown that even insects like cockroaches can develop conditioned reflexes.

 

Pavlov's Experiment

The concept of a conditioned reflex was first demonstrated through Pavlov's famous experiment with dogs, which became known as "Pavlov's dogs." While researching digestion, Pavlov noticed that dogs would start to salivate even when they just heard the sound of the equipment that delivered their food.

 

In his experiment, Pavlov would ring a bell before giving food to the dogs. Normally, dogs would salivate when they saw or smelled food, which is an unconditioned reflex. Pavlov rang the bell every time before feeding the dogs. After repeating this many times, the dogs learned to associate the bell with the food. Eventually, just hearing the bell would make the dogs start to salivate, even if no food was presented. This is a conditioned reflex. Pavlov's research on this phenomenon earned him the Nobel Prize in Physiology or Medicine in 1904.

 

Conditioning: Reinforcement and Extinction

When an animal learns to respond to a stimulus in a new way, this is called "conditioning." For example, in Pavlov's experiment, the dogs’ salivation when eating food is a natural, unconditioned response (UCR). The food itself is an unconditioned stimulus (UCS) because it naturally causes the salivation.

 

The bell, which was used to trigger the response, is called a conditioned stimulus (CS). When the bell is rung and followed by food, the association is reinforced. This repeated pairing of the conditioned stimulus (the bell) with the unconditioned stimulus (the food) is called reinforcement. In Pavlov’s experiment, when the bell is rung and the food is given, the salivation is reinforced.

 

If, however, the conditioned stimulus (the bell) is presented without the unconditioned stimulus (the food) over time, the conditioned response (salivation) will gradually decrease and eventually stop. This process is known as "extinction." In Pavlov's experiment, if the bell rings but no food follows, the dogs will eventually stop salivating at the sound of the bell. Therefore, a conditioned reflex is not permanent and will disappear if the stimulus is not consistently reinforced. This is one of the most basic forms of learning, controlled by connections between nerve cells.