WK9 Reading Pavlovian Learning I

• Pavlovian learning


  A form of associative learning that occurs as a result of incidental experience, named after Ivan Pavlov
• Pavlovian conditioning


  The training procedures used to produce Pavlovian learning, NOT the same as Pavlovian learning
• Pavlovian conditioning


  • Experiences are incidental: they happen to the participant, the participant does nothing to obtain them
  • The experiences may activate the Pavlovian learning process, which is assessed by measuring/recording changes in the participant's behaviour
  • A Pavlovian conditioning procedure may not be successful in producing learning
• Unconditional Stimulus (US)


  A stimulus that elicits a particular response from an animal prior to training (usually the eliciting stimulus of a reflex)
• Unconditional Response (UR)


  A response elicited by the unconditional stimulus prior to training (usually a reflex response)
• Unconditional Reflex


  A reflex that an organism possesses prior to undergoing a Pavlovian conditioning procedure (usually, but not always, an innate reflex)
• Conditional Stimulus (CS)


  A stimulus that is deliberately presented in addition to the US during training and that does not elicit the same response as the US prior to training
• Conditional Response (CR)


  A response elicited by the conditional stimulus after training
• Conditional Reflex


  A reflex that an organism does not possess prior to undergoing a Pavlovian conditioning procedure, it is acquired as a result of the training
• Pavlovian conditioning procedures


  1. Presenting two stimuli, usually repeatedly: one is the US and the other is the CS

  2. The US and CS are often paired close together in time (one trial)

  3. Simultaneous conditioning: US and CS start at the same time

  4. Delay conditioning: CS starts first, then US starts after a delay interval

  5. Trace conditioning: CS starts first, then ends before US starts (trace interval)
• Backward conditioning is also possible, where the US is presented first and the CS second
• Many textbooks provide a distorted and incorrect view of the nature of Pavlovian learning and conditioning based on a simplified account of Ivan Pavlov's original experiments
• Myths about Pavlovian learning and conditioning


  • The CR is the same response as the UR
  • If US-CS pairing leads to CR acquisition, then it doesn't matter how the stimuli are paired, only how close together in time they are
  • US-CS pairing is necessary for learning to occur
  • It's all about reflexes, you start with unconditional reflexes and end up with conditional reflexes
• Many stimulus-elicited behaviours can be 'conditioned' with Pavlovian procedures, not just reflexes
• Conditioned stimulus (CS)


  Stimulus that elicits a conditioned response (CR) after being paired with an unconditioned stimulus (US)
• Unconditioned stimulus (US)


  Stimulus that elicits an unconditioned response (UR) without prior training
• Conditioned response (CR)


  Response elicited by the CS after it has been paired with the US
• Unconditioned response (UR)


  Response elicited by the US without prior training
• The CR is not always the same as the UR
• Examples where CR and UR differ


  • Foot shock US leads to jumping/climbing UR but freezing CR
  • Insulin injection US leads to decreased blood sugar UR but increased blood sugar CR
• How the CS and US are paired matters for CR acquisition
• Eye-blink conditioning procedure


  1. CS (tone) paired with US (mild shock to eyelid)

  2. Delay between CS and US onset varies from -50 ms (backward) to +800 ms (long delay)
• Backward (-50 ms) and simultaneous (0 ms) conditioning do not lead to CR acquisition
• Delay conditioning with CS-US interval between 50-800 ms leads to CR acquisition, with 200-400 ms being most effective
• Even with an effective CS-US pairing, CR acquisition may not occur due to the blocking effect and CS pre-exposure effect
• Blocking effect


  After an animal is conditioned to a CS-A/US pairing, adding a new CS-B to the pairing prevents CR acquisition to CS-B
• CS pre-exposure effect


  Presenting the CS alone before CS-US pairings can prevent or retard CR acquisition
• The Blocking Effect


  1. Animal exposed to conditioning procedure with CS-A paired with US

  2. Animal subsequently exposed to conditioning procedure with CS-A and new CS-B paired with US

  3. Animal produces CR to CS-A but not CS-B
• Blocking Effect


  • Pairing a CS with a US is not sufficient for the animal to learn to respond to the CS, it must also be the case that the animal has not previously learned to produce CRs to any of the other stimuli present (other potential CSs)
• The CS Pre-Exposure Effect


  1. Experimental group exposed repeatedly to a stimulus that will be used as the CS in phase 2

  2. Control group not pre-exposed to this stimulus

  3. In phase 2, control group acquires CR to CS, experimental group may or may not acquire CR to CS, if they do, acquisition is slower and less reliable than in control group
• CS-US pairing is not necessary for acquisition of CRs
• Explicitly unpaired procedure: CS and US presented at irregular intervals, with a long period following each CS during which no US is presented
• CRs are acquired in explicitly unpaired procedure, the type of CR depends on the nature of the US (aversive or appetitive)
• Inhibitory conditioning


  Example of conditioning where CS-US pairing is not necessary for CR acquisition
• Pavlovian learning can occur if the pre-existing reflex (or other stimulus-elicited behaviour) is one that has been previously acquired through conditioning
• Higher order conditioning


  1. Stage 1: Normal conditioning procedure with innate stimulus-elicited behaviour until CR is acquired

  2. Stage 2: Acquired conditional behaviour from stage 1 is conditioned to a new conditional stimulus
• Higher order conditioning demonstrates that the stimulus-elicited behaviour used in conditioning does not need to be innate, it can have been acquired from previous experience
• Pavlovian learning enables animals to predict the occurrence of a stimulus and prepare themselves accordingly
• When CS comes before US


  It signals the imminent arrival of the US and allows the animal to prepare itself accordingly
• Usefulness of Pavlovian learning


  • Animal learns to secrete digestive juices when bell signals food
  • Animal learns to blink when tone signals air puff
  • Animal learns to increase blood sugar when syringe signals insulin injection
  • Animal learns to freeze when tone signals foot shock
  • Animal learns to approach/avoid source of sound when it is not associated with aversive/appetitive US