Classical Conditioning.
Getting its name from the conditions of learning that existed at that time, Classical Conditioning refers to the early experiments of Ivan Pavlov in the 1890's. The famous physiologist established many basic principles of this form of learning. Interesting but a lesser known fact, Classical Conditioning (CC) is also referred to as Respondent Conditioning (RC). I have found that knowledge about this form of learning (as a psychological construct) is a staple of basic psychology courses. Despite being fundamental to the study of behaviour, many people have an inaccurate understanding about it, as reflected in their discourses. So, I thought to explain it in a clear way.
What happened?
Classical conditioning can be best understood by taking a look at Pavlov's experimental design. Let's take a look. He had a dog, who volunteered for Pavlov's psych adventures(that's what I assume). Pavlov rang a bell to which the trusty dog responded with nothing quite special. After giving the dog a look of disapproval (I assume, again), Pavlov decided to train the dog. All the dog-owners know what I am talking about. He trained the dog by sounding the bell, shortly afterward, presenting food. After the sound of the bell had been 'paired' with the presence of food multiple times, he put his training of the dog to the test.
Dr. Ivan Pavlov measured the amount of saliva the dog's mouth produced when he rang the bell and did not produce the food. Here's the finding of this experiment, the dog produced certain amount of saliva when the sound of the bell was presented. Pavlov, amazed at this finding did what any good scientist would have done. He replicated this experiment and re-performed it. He found that with subsequent training of the dog, the amount of saliva produced as the bell rang increased! Thus, the conclusion was that the dog was trained to salivate whenever the bell was rung; it became to be known as the conditioned response.
The Terms of the Experiment
In a classical conditioning experiment, two types stimuli (anything that evokes a response) are produced to the learner. They are called Conditioned Stimulus (CS) and Unconditioned Stimulus (US). Conditioned stimulus evokes an alerting response the first few times its presented. The bell Pavlov used is a good example of a CS. Literally, anything that can be noticed during an experiment is a CS. US, on the other hand, reliably evokes a response. This is called the Unconditioned Response (UR). Here's where things get interesting.
The idea becomes to combine the CS with the US. In the above case, it meant pairing the sound of the bell with the presentation of food. Pairing means to present the CS, a few fractions of a second before the US. After the CS and the US have been 'paired' several times i.e., for several trials, presence of a CS produces the UR. That is classical conditioning in a nutshell, precisely. This idea and its presentation to the scientific community did wonders to research on how learning happens. Psychologists, later opened unto an entirely new field of Behaviourism. The idea that human behaviour can learned by measuring responses to stimuli they are presented with.
The Relevance
It might sound basic to us now but back in the 1890's, I can imagine, it must've been a huge deal! In that era this finding opened the doors for psychological researchers to finally study learning in a way that was scientific. It was falsifiable, replicable and result-oriented. We had a tangible measure of a fundamental psychological construct and that, could not have been a small feat. So, you can easily understand that it might be a little irksome to Pavlov and all the great behaviourists who came after him, when people don't understand these ideas correctly.
I also don't understand when people say that these theories are outdated. There is a negative connotation attached to that line. Sure, I agree that it has been quite some time since these theories on learning came out and newer theories have replaced them. However, the newer theories (I mean the ones that have stood the test of time and science) are based of and stand on the shoulder of these classical theories. The basic principles are the same for let's say some of the work done by Karl Lashley and Ivan Pavlov. I invite you to use this refresher paragraph on CC and think of examples from your life where you can attribute some UR with some CS. It's really fun!
Keep thinking,
Anand
Some other helpful videos that explain CC in a clear and concise manner. Please watch them to gain a better idea and reliable idea of CC and its origin.
Prof. Zimbardo's Video on CC: https://www.youtube.com/watch?v=hhqumfpxuzI