Chapter 3: Pavlovian Conditioning Notes

Introduction to Pavlovian (Classical) Conditioning

  • Definition: Pavlovian conditioning, also known as classical conditioning, is a procedure involving the pairing of a neutral stimulus (NS) with an unconditioned stimulus (US) to elicit a conditioned reflex response.

  • Originator: Ivan Pavlov, a Russian physiologist, discovered this phenomenon while studying digestion and salivation in dogs.

    • Observation: Pavlov's dogs began salivating when they saw his assistants entering the laboratory at feeding time.

    • Deduction: He deduced that the dogs had learned to associate the assistant's presence with food.

    • Hypothesis: This led him to investigate if dogs could be trained to respond to other stimuli.

Types of Reflexes

  • Pavlov concluded that dogs developed a reflex response to a signal indicating approaching food, such as the feeder's presence.

  • This observation led to the hypothesis of two types of reflexes:1. Unconditioned Reflexes: These are innate, largely present from birth, and do not fade over time.- Example: Salivating in response to food, as the body innately prepares to ingest and digest it.
    - Key Characteristic: No learning or experience is required.

    1. Conditioned Reflexes: These are developed through experience, are less universal across a species, and can change or fade over time.- Key Characteristic: Acquired through learning and association.

Components of Pavlovian Conditioning
Unconditioned Reflexes

  • Consist of two elements:- Unconditioned Stimulus (US): A stimulus that elicits a response from the organism without any prior learning or training.- Examples: Food, painful stimulus, loud noise.

    • Unconditioned Response (UR): A reflexive response to a US that occurs naturally, without any learning or training.- Examples: Salivation (to food), fear response (to painful stimulus), flinching (to loud noise).

  • The US-UR relationship is an innate, naturally occurring one.

Conditioned Reflexes

  • Also consist of two elements:- Conditioned Stimulus (CS): An initially neutral stimulus (NS) that, after learning/acquisition has occurred through pairing with a US, comes to elicit a response from the organism.

    • Conditioned Response (CR): A reflexive response to a conditioned stimulus that occurs without the presence of the US.

  • The CS-CR relationship is one that must be learned (conditioned).

  • Neutral Stimulus (NS): The conditioned stimulus always begins as a neutral stimulus. An NS is a stimulus that does not elicit an inherent, reflexive response before conditioning.- Example: The presence of the lab assistant initially had no effect on the dog's salivation, but it became meaningful (a CS) after repeated pairings with food (US).

Stages of Conditioning & Definitions

  • Before Conditioning:- US (Food) -> UR (Dog salivates)

    • Neutral Stimulus (Bell) -> No response (No salivation)

  • Conditioning (Acquisition):- Repeated pairing of NS (Bell) with US (Food).

  • After Conditioning:- CS (Bell) -> CR (Dog salivates)

Formal Definitions of Components:

  • Unconditioned Stimulus (UCS/US): The event or stimulus that naturally produces the unconditioned response.

  • Unconditioned Response (UCR/UR): The automatic reaction to a natural stimulus.

  • Neutral Stimulus (NS): A stimulus that has no particular meaning to the organism and does not elicit an instinctive response.

  • Conditioned Stimulus (CS): A previously neutral stimulus that an organism learns to associate with the UCS.

  • Conditioned Response (CR): The learned behavior an organism performs when presented with the CS alone.

    • Example from Pavlov: Food (US) naturally causes Salivation (UR). A Tone (before pairing) (NS) causes No Salivation. After pairing, the Tone (after pairing) (CS) causes Salivation (CR).

Identifying Components of Classical Conditioning

  • To help identify the components:1. What reflex response occurs before conditioning? (This is the UR)

    1. What stimulus elicits that response before conditioning? (This is the US)

    2. What reflex response occurs as a result of conditioning? (This is the CR)

    3. What stimulus elicits that response after conditioning? (This is the CS)

  • Bonus Tip: If you identify the CS, you have already identified the NS because they are the same stimulus, just at different stages of conditioning.

Measuring Pavlovian Conditioning
Initial Acquisition

  • Acquisition has occurred when the NS can be presented alone and elicit a response without the US. At this point, the NS officially becomes a CS, and the response becomes a CR.

Strength of Conditioning

  • The strength of conditioning can be measured by:- Latency: The CR begins very quickly (shorter latency) after the CS is presented. A shorter latency indicates stronger conditioning.

    • Intensity: The CR becomes stronger or more pronounced over time. (e.g., trembling vs. full panic, a few drops of saliva vs. a flow of drool).

Higher-Order Conditioning

  • Definition: A variation of classical conditioning where a neutral stimulus (NS2) is paired with an already well-established conditioned stimulus (CS1) instead of a US.

  • Process: Once an organism has been conditioned to respond to an initial CS1 (e.g., a tone), that CS1 can then function as if it were an unconditioned stimulus in subsequent conditioning trials for a new NS_2.

  • Underlying Principle: The organism learns that CS1 predicts the US. This learned predictive power allows CS1 to substitute for the US in training a new CS_2.

Diagrammatic Representation:

  1. Standard Classical Conditioning (First-Order):- US (Food) -> UR (Salivation)

    • NS1 (Metronome) + US (Food) -> UR (Salivation)- Resulting in: CS1 (Metronome) -> CR (Salivation)

  2. Higher-Order Conditioning (Second-Order):- NS2 (Light) + CS1 (Metronome) -> CR (Salivation)- Resulting in: CS_2 (Light) -> CR (Salivation)

Characteristics of Higher-Order Conditioning

  • The response to the secondary CS2 is often weaker than the response to the original CS1.

  • Theoretical Extension: Conditioning could theoretically continue with CS3, CS4, and so on. However, the original US must elicit a very strong response to maintain effectiveness through multiple orders.- Example: Particularly aversive stimuli, like pain, have been shown to be effective up to fifth-order conditioning.

  • Utility: Higher-order conditioning is useful because it allows organisms to learn associations with new stimuli based on existing associations.- Real-World Example: After being stung by a wasp, you fear wasps (CS1) due to their association with pain (US). If you then hear wasps buzzing in a shed (NS2) in your backyard, you might begin to fear the shed (CS2) because you now associate the shed with wasps (CS1).

Variables Affecting Pavlovian Conditioning
1. How the NS & US are Paired

  • There are four primary ways to pair the NS and US:

    • Trace Conditioning: The NS begins and ends entirely before the US is presented. There is a temporal gap between the end of the NS and the onset of the US.- Example: The tone plays for 3 seconds, then stops. After a brief pause, food is presented.

      • Requirement: Requires the organism to remember that the NS occurred (involves working memory).

    • Delayed Conditioning: The NS and US overlap slightly. The NS begins and remains present until the US is presented, or until the US starts and then overlaps for a short period.- Example: The tone plays for 3 seconds, and the food is presented while the tone is still playing.

      • Efficacy: Can produce a conditioned response more quickly and reliably because it ensures the organism associates the NS with the US.

    • Simultaneous Conditioning: The NS and US are presented at the exact same time, with their onsets coinciding.- Example: The onset of the tone and presentation of food occur simultaneously.

      • Efficacy: Produces a weaker response and may not lead to association, as the NS does not reliably predict the US (lack of contingency).

    • Backward Conditioning: The NS is presented after the US, with the US occurring first.- Example: Food is presented, and then the tone is played.

      • Efficacy: Very difficult to produce a CR because the NS must predict the US for effective conditioning. If the NS comes after, it cannot be a predictor.

  • General Efficacy: Trace and Delayed conditioning are generally more effective. Simultaneous and Backward conditioning are less effective most of the time but can be useful in specific, specialized circumstances.

    • Decision Tree for Pairing Types:- Was the CS presented before the US?- No: Backward
      - Yes: - Was the CS removed before the US appeared?- Yes: Trace
      - No: (Meaning CS and US overlap)- Was the CS presented at the same time as the US?- Yes: Simultaneous
      - No: Delayed (meaning CS started before and overlapped with US)

2. NS-US Contiguity (Temporal Proximity)

  • Definition: Refers to how near the NS and US are presented to each other in time.

  • Interstimulus Interval (ISI): The interval between the NS and US.- For trace conditioning, this is the time between the end of the NS and the onset of the US.

    • For delayed conditioning, this is the interval between the NS starting and the US starting.

  • Optimal ISI: The ideal ISI depends on the nature of the conditioned response.- Very brief ISIs work for some responses (e.g., eyeblink conditioning).

    • Longer ISIs are useful for others (e.g., a fear response; fear of dogs is more likely after a sustained attack than a single, brief snap, suggesting a longer effective ISI).

3. Stimulus Features

  • While almost any NS can become a CS, some are more effective due to their characteristics:- Intensity of NS: Stronger or more intense stimuli generally act as better CSs.

    • Overshadowing: More intense stimuli can overshadow weaker stimuli when presented as a compound stimulus (two neutral stimuli presented together).- Example: If stung by a wasp in a forest, you might hear buzzing and crunching leaves. The more intense buzzing is more likely to be associated with pain and elicit fear than the quieter crunching leaves.

    • Nature of US: The type of US also matters. Painful stimuli, illness, and bad tastes tend to create some of the strongest and most enduring conditioned responses (e.g., taste aversion).

4. Prior Experience with the NS and US

  • An organism's previous exposure to the NS can interfere with learning.- Latent Inhibition: The failure to condition a response as a result of prior exposure to the NS without the US.- Explanation: Unfamiliar (novel) stimuli are more readily conditioned than familiar stimuli. If an organism regularly encounters an NS without any P-US association, that NS becomes less likely to form a strong association with a subsequent US.
    - Adaptive Significance: Imagine a rabbit attacked by a coyote while in grass. It's more adaptive to fear the novel coyote scent than the familiar grass it lives in.
    - Analogy: Similar to habituation, familiar or redundant stimuli encountered regularly become more difficult to associate with a new response.

5. Number of NS-US Pairings

  • Generally, repeated pairings are required for conditioning to occur. More pairings often lead to stronger conditioning, up to a point.

6. Intertrial Interval

  • Definition: The time between pairings or