L2 Classical Conditioning (PSYC2050)

• PSYC2050 course material being reviewed
• Professor Paul E. Dux is in 463 McElwain Building
  • Email at [email protected] or [email protected]
  • Website is www.qaclab.org

Classical (Pavlovian) Conditioning

• Also known as general principles, it involves associations

Previously

• Habituation does not require linking stimuli together
• Habituation is the simplest type of learning
• Habituation includes decline/disappearance of a reflexive response when the same stimulus is repeatedly presented
  • This includes infant looking behaviour and startle response in rats
• Important and repetitive events are ignored during habituation

Learning lectures weeks 2-5

• Two forms of associative learning are being reviewed
• Classical conditioning and operant conditioning
• Ivan Pavlov is associated with classical conditioning for lectures 2 + 3
• B.F. Skinner is related to operant conditioning for lectures 4 + 5

Learning Objectives

• Understand the basic logic of learning via association
• Identify the main components & phases of a prototypical classical conditioning experiment
• Distinguish the different learning processes that can occur within a classical conditioning experiment and the nature of these processes
• Identify the design factors that influence classical conditioning and describe how they do so

Free Energy Principle

• Consists of a theory about how the brain works
  • Karl Friston proposed the Free Energy Principle in 2010
  • He wrote about it in Nature Reviews Neuroscience
• Aims to give a unified account of action, perception, and learning for adaptive systems
• It is a formulation of how adaptive systems resist a natural tendency to disorder
• Any self-organizing system at equilibrium with its environment must minimize its free energy
• Biological systems must maintain their states despite a constantly changing environment
• The physiological and sensory states in which an organism can be is limited and have a low entropy
• Entropy is surprise and a 'fish out of water' has a high entropy
• Biological agents must minimize the long-term average of surprise to keep sensory entropy low
• Minimizing surprise or maximizing the sensory evidence for an agent's existence
• Free energy principle represents a predictive/Bayesian brain

Classical (Pavlovian) Conditioning

• Discovered by a Russian physiologist while studying the digestive system and salivation
• Pavlov observed salivation in dogs before food was placed in their mouths
• He accidently discovered classical conditioning
• When food was placed in the animal’s mouth, the natural reflexive response of salivation occurred & was measured
• Other stimuli don’t elicit that response
• Pavlov's experiments: dogs that had been through the testing procedure several times would begin to salivate even before the food was placed in their mouth
• It was demonstrated that footsteps, clanging of food dish, bell and whistle elicited stimulatory response over time

Elements of classical conditioning

• Four elements:
  • Unconditioned stimulus (US)
  • A stimulus that elicits an unlearned response
  • Unconditioned response (UR)
  • The unlearned response to a US
  • Conditioned stimulus (CS)
  • A stimulus to which an organism must learn to respond
  • Conditioned Response (CR)
  • The response to a CS (which is learned)
• Unconditioned connection between stimulus and response is INNATE
• Conditioned = connection between stimulus and response is LEARNED

Phases of a typical conditioning experiment

• 3 Stages measured by response (UR/CR)
• Habituation stage 1
  • CS presented alone
• Acquisition stage 2
  • CS presented along with US
• Extinction stage 3
  • CS presented alone again

Two factors

• Factors influencing the acquisition curve:
  • Intensity of the US: more intense provides more rapid learning
  • Order and timing: the CS coming before the US is better

Classical conditioning in Clinical applications

• Acquisition of fears, phobias, and other maladaptive behaviors can arise
• Treatment of the fears, phobias, and other maladaptive behaviors can change the CR
  • E.g. Flooding

Conditioned Fear

• 1920 experiments by Watson & Rayner
• Little Albert experiments included acquisition of emotional responses
• In experiments, fear generalized beyond initial conditions

Temporal conditioning

• CR happens at a specific time, even without a clear CS
  • People wake up at the same time every day without an alarm

Traditional Example in Real-World Environments

• School near cafes → students associate lunch break with the smell of food
• Foxes eating from rubbish bins

Ideal Delayed Stimulus Intervals (ISI) for Learning

• Best timing between CS and US:
  • Auditory stimuli → ~200ms-2 seconds
  • Digestion-related stimuli (e.g., taste aversion) → longer intervals

Timing

• Delay Conditioning-Short: PC chime and Mint (CS and US) overlap slightly
• Delay Conditioning-Long: PC chime and Mint (CS and US) overlap moreso
• Trace Conditioning: PC chime and Mint (CS and US) don't overlap, small interval between them
• Simultaneous Conditioning: PC chime and Mint (CS and US) start and end at the same time
• Backward Conditioning: Mint appears before PC chime (US before CS)
• Temporal Conditioning: 6pm and Food (CS and US) start and end at the same time

Optimal ISI for Eyelid Reflex

• Occurs at ~200ms

Optimal ISI for Taste Aversion

• Occurs just under 0.5 hours

Types of Pavlovian Conditioning

• Excitatory conditioning
  • CS predicts the occurrence of US
  • example: if 'A' is a bell… A-US, A-US, A-US
• Inhibitory conditioning
  • CS predicts absence of US
• example: if 'B' is a light… A-US, A-US, AB, A-US, AB
• B predicts the absence of US

Inhibitory Conditioning

• A-US, A-US, A-US A leads to a CR (excitatory conditioning)
• A-US, AB-nothing, A-US, AB-nothing --> B?
• The animal learns that B predicts the absence of US and therefore doesn’t make a CR (inhibitory conditioning)
• To test animal knowledge, use summation test and retardation tests
  • An inhibitor must pass both

Retardation test

• First inhibitory conditioning takes place
  • A-US, AB-nothing, A-US, AB-nothing -->
  • B becomes inhibitor 'I
• To test it train an inhibitor 'I' and a neutral stimulus 'N' to become excitatory
  • I-US, I-US, I-US
  • N-US, N-US, N-US
• Slower learning to inhibitor: I < N

Summation test

• First inhibitory conditioning takes place
  • A-US, AB-nothing, A-US, AB-nothing -->
  • B becomes inhibitor 'I
• Test it by presenting:
  • A new excitatory CS alone: 'N', New excitatory CS + the inhibitor: N+I
• N+I < N, meaning the combo should evoke a weaker CR

Extinction & Spontaneous Recovery

• Over time, showing CS without US brings CR to zero
• If CS is reintroduced after a break, the CR may return ("spontaneous recovery").
• Renewal Effect: If extinction occurs in one environment but the CS appears in another then the CR is recovered

Reinstatement & Disinhibition

• Reinstatement: A strong US reintroduces the CR automatically
• Disinhibition: If an unexpected stimulus (like a loud noise) occurs during extinction then it can temporarily bring back the CR

Additional phenomena

• Spontaneous recovery occurs when reintroducing the CS after a "break" and The CR reappears
• renewal: when extinction is context specific
  • Acquisition in context X
  • Extinction in context Y
  • present CS in context X results in CR
• reinstatement: (Reminder Effect)
  • present US alone after extinction
  • Then Present CS = CR

Typical Classical Conditioning Experiment

• In Stage 1: Habituation CS is presented alone and ensures that the CS is not already associated with the US
• In Stage 2: Acquisition CS is paired with the US and More trials → Stronger CR (learning occurs)
• In Stage 3: Extinction CS is presented alone during which CR weakens until it disappears and in clinical settings, extinction-based conditioning is used to treat phobias

What happens during extinction?

• It is not simply erasing whatever association was formed during acquisition.
• Still hotly debated, is it inhibition theory or ambiguous stimulus?

Hidden Assumptions of Classical Conditioning

• Any two stimuli can be paired together (equipotentiality)
• The more two stimuli are paired, the stronger the individual will associate them (contiguity)
• Conditioning changes trial to trial in a regular way (contingency)
• Blocking and Superconditioning show that these assumptions incorrect.

Blocking

• Kamin conducted blocking experiments in 1968
• Rats divided into 'Blocking' and 'Control' groups
• In the control group
  • Rats saw both a light and heard a noise and then got shocked
  • This was repeated until rats developed a CR
• Kamin then tested whether the rat reacted to just the light by trying to avoid being shocked, and they did
• In the blocking group
  • rats heard a noise and then got shocked until they developed a CR
  • rats then heard the noise and saw the light and then got shocked
• Kamin then tested whether the rat reacted to the light by trying to avoid being shocked, but they didn't
• Blocking Effect: Rats in both the blocking and control groups had seen the light and then been shocked exactly as many times, however, the rats reacted differently
• Pairing the light with the shock didn't lead to conditioning
• The control group and blocking group had the noise+light/shock pair the exact same amount of times

Superconditioning

• The Opposite of blocking rescorla's findings in 1971
• Some rats were played a tone in the absence of a shock - tone became cue of safety (Inhibitor)
• Later rats were presented the tone with a light followed by a shock
• Finally rats were presented the light alone – rats in this group showed stronger conditioning to the light than rats in a control group
• Superconditioning - When a neutral stimulus and an inhibitory stimulus together are paired with the US.
• The learner forms a stronger association between the neutral stimulus and the US

Conservation Example: Eastern Quoll

• Eastern quolls are becoming extinct due to cane toads
• They eat cane toads and are poisoned
• Scientists (CSIRO) captured several quolls for lab studies
• They introduced juvenile quolls to cane toads with modified poison glands (covered them with a substance that induces nausea and vomiting)
• This created a negative association with cane toads as prey
• When released into the wild, these quolls no longer ate cane toads

Conditioning Example – Eye-Blink Conditioning

• Participants are randomly blown in the eye (unconditioned stimulus)
• They blink (unconditioned response)
• An auditory tone (neutral stimulus) is played before the air puff
• Eventually, the tone becomes associated with the air puff (conditioned response)
• Participants begin to blink when hearing the tone, even if the air puff is not present (blinking to the tone is the conditioned response)

Readings

• Learning section Mazur: Chapters 2 & 3
• Dunsmoor, J.E., Niv, Y., Daw, N., & Phelps, E.A. (2015). Rethinking extinction. Neuron, 88, 47- 63
• Olsson, A., Ebert, J.P., Banaji, M.R., & Phelps, E.A. (2005). The Role of Social Groups in the Persistence of Learned Fear. Science, 309, 785-787