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Classical Conditioning Mechanisms and Their Determinants

Classical Conditioning Mechanisms

Pavlov’s Stimulus Substitution Theory

  • Core Idea: An animal treats the Conditioned Stimulus (CS) as a substitute for the Unconditioned Stimulus (US), leading to the production of the Conditioned Response (CR).
  • Examples fitting the theory:
    • Pavlov: Unconditioned Response (UR) = salivation, CR = salivation.
    • Autoshaped food and water peck CRs in pigeons: The CR (pecking) resembles the UR (eating/drinking behavior).
    • Cocaine: UR = activity, CR = activity (in anticipation of cocaine).
    • Cyclophosphamide (chemotherapy drug): UR = immune suppression, CR = immune suppression (conditioned).

Limitations of Stimulus Substitution Theory

  • CR doesn't always resemble the UR: The theory is incomplete because the CR does not always mirror the UR.
    • Example: Fear CRs in rats with shock US: UR = leaping, but CR = freezing. This shows a divergence in topography.
  • Determinants of CR Nature: Modern understanding identifies four key factors that determine the nature of the CR (how CS-US associative learning translates into behavioral changes):
    1. The US (Unconditioned Stimulus).
    2. The CS (Conditioned Stimulus).
    3. The Interstimulus Interval (ISI).
    4. CS and US must belong together (biological preparedness).

1. Determinant of CR Nature: The US

  • Impact of US: The specific Unconditioned Stimulus plays a crucial role in shaping the Conditioned Response.
  • Example (Heroin Withdrawal): An heroin addict experiences severe withdrawal symptoms (CR) upon seeing the dealer's door (CS), which has been previously associated with drug-seeking and administration (US).
  • Opiate Administration/Withdrawal Symptoms:
    • Initial Administration (UR): Hyperthermia, decreased blood pressure, skin flushed and warm, miosis (pinpoint pupils), constipation, respiratory depression, antitussive (cough suppression), relaxation.
    • Withdrawal (Opposite/Compensatory Effects): Hypothermia, increased blood pressure, chilliness and gooseflesh, mydriasis (dilated pupils, as shown in the image on page 6), lacrimation, yawning and panting, sneezing, restlessness.
  • Conditioning of the b-process (Siegel's Compensatory-Response Model):
    • Baseline (A): Response to the drug before conditioning (e.g., euphoria).
    • After Conditioning (B): Response to the CS alone is often a compensatory response (b-process), which is opposite to the drug's direct effect (e.g., dysphoria in drug-associated contexts).
    • After Conditioning (C): Response to the CS plus the drug shows a attenuated (reduced) drug effect due to the conditioned compensatory response.
  • Drug Conditioning Trial Example (Heroin):
    • Pre-Drug CSs: Dealer,