Introduction to Classical Conditioning

Event-Event learning (classical or Pavlovian conditioning) experiments


  1. To look for evidence of the ability to learn that two or more events are related (correlated). This form of associative learning allows the learner to use one event to predict the occurrence of the other event.
  2. To provide an explanation of the mechanism (cause) of event-event learning.


Classical Conditioning (CC) procedures (first introduced by Pavlov) are used. All CC procedures include:

the presentation of Stimuli (CS & UCS) and the recording of Responses (CR & UCR).

There are many different classical conditioning paradigms. Which stimuli are presented and which responses are measured depends on the particular paradigm; examples include:

Conditioned salivation
Sign tracking (or conditioned keypecking or autoshaping)
Conditioned Eyeblinking (or Conditioned Nictitating Membrane response; NMR)
Taste Aversion Learning
Conditioned suppression (or conditioned emotional response; CER)

You should be able to identify the CS, UCS, CR and UCR for each of these paradigms.

Typical dependent variables in classical conditioning experiments:

Percent of trials with a CR
Probability of a CR
CR Amplitude
Suppression ratio (common in Conditioned suppression experiments)

An independent variable in most classical conditioning experiments is

Number of temporally contiguous CS-UCS pairings

Some of the Control variables in a classical conditioning experiment include

ISI (Interstimulus interval)
ITI (Inter Trial Interval)
Type (Quality) of CS (e.g., pitch of a tone or color of a light)
Type (Quality) of UCS (e.g., food, puff of air to eye, or electric shock to feet)
Intensity (strength) of the CS and UCS(e.g., mild shock or moderate shock)
Total number of CS-UCS pairings (trials)
The temporal relationship between the CS and UCS (e.g., delay, simultaneous, backward, trace, or backward)
The relationship or correlation between a CS and UCS (e.g. positive correlation, negative correlation or no correlation)

Other independent variables may include any of the control variables (if so, then it is no longer a control variable, but an independent variable because it is being manipulated by the experimenter) as well as many other variables.


Acquisition of classically conditioned responses (CRs) (often simply referred to as conditioning)
Extinction of CRs
Spontaneous Recovery of an extinguished CR


  1. Preferred hypothesis: Behavior change (e.g., the ACQUISITION of Conditioned Responding) is presumed to be a cause of associative learning (a reorganization of nervous system functioning that allows an animal to use one event (the CS) to predict the occurrence of another biologically-important event (the UCS), thereby improving the animal’s ability to live successfully in its environment)
  2. Alternative Hypothesis #1: Behavior change (e.g., acquisition or conditioning) is not true conditioning but a case of sensitization.
  3. Alternative Hypothesis #2: Behavior change is not true conditioning but a case of pseudoconditioning.


    1. Prove alternative hypotheses to be incorrect (Which observations proved the alternative hypotheses to be incorrect?)

    2. Provide evidence in support of the preferred explanation (hypothesis)

    3. Provide additional observations that will lead to a further understanding of event-event learning.


Other Variables affecting conditioning

Salience of stimuli (intensity, previous experience, and species-specific adaptations)
Qualitative Relations between CS & UCS (Garcia & Koelling's classic study)
Constraints on conditioning.