Classical Conditioning: Foundations
The Early Years of Classical Conditioning
- Studies of classical conditioning began with the work of Russian physiologist
o Started when he noticed that dogs created psychic secretions every
time they were presented food.
Discoveries of Vul’fson and Snarskii
- Performed the first systematic studies of classical conditioning.
- Vul’fson focused on salivary glands.
o Studied salivary responses to various substances placed in the mouth:
dry food, wet food, sour water and sand for example.
o If they had the food placed in their mouth repeatedly, the mere sight
of these foods was enough to make them salivate.
- Snarskii extended the studies with the use of artificial substances.
o Used different colors to color bowls of water.
- Some substances produced distinctive taste and texture sensations in the
mouth, known as orosensory stimuli.
- First time only the feeling of sand in dogs mouth elicited salivation, however
after the sand had been placed in the mouth several times the sight of sand
also came to elicit salivation.
o The association of one feature of an object with another is called
- To study the mechanisms of associative learning, the stimuli to be associated
have to be manipulated independently of one another.
o Pavlov used procedures in which the stimuli to be associated came
from different sources.
The Classical Conditioning Paradigm
- Involves two stimuli: one of these stimuli is a tone or a light. The other
stimulus is food or the taste of sour solution placed in the mouth. In contrast
to the light or tone, the food or sour taste elicits vigorous salivation even the
first time it is presented.
o The light or tone referred to as conditional stimulus b/c the
effectiveness of this stimulus in eliciting salivation depended pairing it
several times with the presentation of food.
o The food or sour taste was called the unconditioned stimulus b/c its
effectiveness in eliciting salivation did not depend on any prior
o The salivation that eventually came to be elicited by the tone or light
was called the conditioned response, and the salivation that was always elicited by the food or sour taste was called the unconditioned
- Pavlov used dogs using salivary-fistula technique.
- Most contemporary experiments on Pavlovian conditioning are carried out
with rats, rabbits, and pigeons.
- Little Albert Experiment
o Conditioned rat (CS) with loud abstract noise (US) and made little
Albert afraid (CR) of the rat.
- When rats are scared they become immobile.
- Two different indirect measures of immobility known as conditioned
suppression procedures are:
o Lick Suppression Procedure: rat licking a spout of water, then
presented with a fear CS (i.e. tone). Now measure how long it takes to
lick a certain amount of times.
o Conditioned Emotional Response: rats are first trained to press a
response lever for food reward in a small chamber. Once the rats are
pressing the lever at a steady rate fear conditioning is introduced
consisting of a tone or light paired with a brief shock. As they acquire
the conditioned fear, they come to suppress their level pressing
during the CS. They calculate a ratio and compare to the normal
Eye Blink Conditioning
- Puff of air to the eye (US) was given when a tone was heard (CS). Eventually
began to blink when they heard the tone.
- One experimental paradigm that has contributed significantly to modern
conceptions of Pavlovian conditioning is the sign tracking (autoshaping).
o Not a highly reflexive response like salvation and blinking.
- Sign tracking is investigated by presenting a discrete, localized visual
stimulus just before each delivery of a small amount of food.
o I.e. Pigeon in a chamber with a small circular key that could be
illuminated and that the pigeons could peck. Periodically the pigeons
were given access to the food for a few seconds. The key light was
illuminated for 8 seconds immediately before each food delivery.
o Instead of using the key light to tell them when they should go the
food dish, they started pecking the key itself. o Interesting behavior discovery b/c the key was not needed to gain
access to the food.
- For sign tracking to occur the CS has to be of the proper modality and
Learning What Tastes Good or Bad
- A conditioned taste aversion is learned if ingestion of a novel flavor is
followed by an aversive consequence such as indigestion or food poisoning.
- In contrast a taste preference may be learned if a flavor is paired with
nutritional repletion or other positive consequences.
o This can happen in just one trial and the learning can even occur if the
illness is delayed several hours after ingestion of the food.
- In 20% of the cases, individuals believed that their illness was not the result
of the food they ate. This indicates that food aversion learning can be
independent of rational thought processes and can go against a person’s
conclusions about the causes of their illness.
- I.e. eating before chemotherapy, most people think their loss of appetite is
caused by the chemo, but it could be that eating before produced a taste
- Taste aversion learning is a result of the pairing of a CS (taste) and a US (drug
injection or radiation exposure) in much the same manner as in other
examples of classical conditioning. However it does have some special
o 1. Strong taste aversions can be learned with just one pairing of the
flavor and the illness.
o 2. Taste aversion learning occurs even of the illness does not occur
until several hours after exposure to the novel taste.
- Evaluative Conditioning: when our evaluation or liking of a stimulus
changes by virtue of having that stimulus associated with something we
already like or dislike.
o Used extensively in the advertisement industry.
Excitatory Pavlovian Conditioning Procedures
- So far we have been learning excitatory Pavlovian conditioning.
- In excitatory conditioning, organisms learn an association b/w the
conditioned and unconditioned stimuli.
o As a result of the association, presentation of the CS activates
behavioral and neural activity related to the US in the absence of the
actual presentation of the US.
Common Pavlovian Conditioning Procedures
- Major factor that determines the course of classical conditioning is the
relative timing of the CS and US. - Five Common Classical Conditioning Procedures:
o Short-delayed Conditioning:
Most frequently used.
Involves delaying the start of the US slightly after the start of
the CS on each trial.
Critical feature is that the CS starts each trial and the US is
presented after a brief delay. The CS may continue during the
US or end when the US begins.
o Trace Conditioning:
Similar to short delayed procedure.
However in trace conditioning, the US is not presented until
some time after the CS has ended.
This leaves a gap b/w CS and US called the trace interval.
o Long-delayed Conditioning:
In this case the US is delayed much longer (5-10 mins) than in
the short delayed conditioning.
Does not include a trace interval.
The CS lasts until the US begins.
o Simultaneous Conditioning:
Presents the CS and US at the same time.
o Backward Conditioning: