Lecture 8: Learning – Classical and Operant Conditioning

Learning

Introduction to Learning

Learning is the process by which behaviour or knowledge changes as a result of experience. In psychology, learning is often studied through the relationship between a stimulus (S) and a response (R). Key questions include whether learning is automatic, how it can be acquired, and what factors influence the increase or decrease of a response.

• Stimulus (S): Any event or object in the environment that elicits a response.

• Response (R): The behaviour or reaction to a stimulus.

• Learning: Change in behaviour or knowledge due to experience.

Classical Conditioning

Definition and Key Concepts

Classical conditioning (also known as Pavlovian conditioning) is a type of learning in which an association is acquired between a neutral stimulus (NS) and an unconditioned stimulus (US) to produce a change in response (R).

• Unconditioned Stimulus (US): A stimulus that naturally elicits a response (e.g., food).

• Unconditioned Response (UR): The natural reaction to the US (e.g., salivation).

• Neutral Stimulus (NS): A stimulus that does not initially elicit the UR (e.g., metronome).

• Conditioned Stimulus (CS): The NS after association with the US (e.g., metronome after pairing).

• Conditioned Response (CR): The learned response to the CS (e.g., salivation to metronome).

Pavlov's Dogs Example

• US: Food

• UR: Salivation

• NS: Metronome

• After repeated pairing of NS (metronome) with US (food), the NS becomes a CS.

• CS: Metronome

• CR: Salivation to metronome

Example: Pavlov's experiment demonstrated that dogs could learn to salivate to a previously neutral stimulus (metronome) after it was repeatedly paired with food.

Little Albert Experiment

• US: Loud noise

• UR: Fear response

• NS: White rat

• After pairing the NS (white rat) with the US (loud noise), the NS becomes a CS.

• CS: White rat

• CR: Fear response to white rat

Example: The Little Albert study showed that emotional responses (like fear) could be conditioned in humans.

Processes of Classical Conditioning

• Acquisition: The initial phase of learning when a response is first established.

• Extinction: Reduction in the conditioned response (CR) when the conditioned stimulus (CS) and unconditioned stimulus (US) are no longer paired.

• Spontaneous Recovery: The reappearance of a previously extinguished CR after a period of non-exposure to the CS.

Example: If a dog stops salivating to a metronome after it is no longer paired with food (extinction), but later salivates again when hearing the metronome (spontaneous recovery).

Operant Conditioning

Definition and Key Concepts

Operant conditioning is a type of learning in which the relationship between stimulus and response is influenced by the consequences of the behavior. Behaviors are strengthened or weakened depending on whether they are followed by reinforcement or punishment.

• Reinforcement: Any consequence that increases the likelihood of a behavior.

• Punishment: Any consequence that decreases the likelihood of a behavior.

• Positive: Adding a stimulus.

• Negative: Removing a stimulus.

Principles of Operant Conditioning

• Positive Reinforcement: Adding a pleasant stimulus to increase behavior (e.g., giving a treat).

• Negative Reinforcement: Removing an unpleasant stimulus to increase behavior (e.g., turning off a loud noise).

• Positive Punishment: Adding an unpleasant stimulus to decrease behavior (e.g., scolding).

• Negative Punishment: Removing a pleasant stimulus to decrease behavior (e.g., taking away a toy).

• Avoidance Learning: Behavior prevents the possibility that a stimulus will occur.

• Escape Learning: Behavior removes a stimulus that is already present.

Example: In Skinner's box, a rat learns to press a lever to receive food (positive reinforcement) or to avoid a shock (negative reinforcement).

Processes of Operant Conditioning

• Primary Reinforcer: Naturally reinforcing (e.g., food, water).

• Secondary Reinforcer: Learned reinforcer (e.g., money, praise).

• Discriminative Stimulus: A cue indicating whether a response will be rewarded.

• Discrimination: Learning to respond to the original stimulus but not to similar ones.

• Generalization: Response occurs to new, similar stimuli.

Example: A rat presses a lever only when a light is on (discriminative stimulus), but not when the light is off.

Reinforcement Schedules

Reinforcement schedules determine how and when a behavior is followed by a reinforcer. These schedules affect the rate and stability of learning.

Schedule Type	Description	Example
Fixed Ratio (FR)	Reinforcement after a set number of responses	Factory worker paid for every 10 items produced
Variable Ratio (VR)	Reinforcement after a variable number of responses	Slot machine payout
Fixed Interval (FI)	Reinforcement after a set period of time	Weekly paycheck
Variable Interval (VI)	Reinforcement after a variable period of time	Checking for a randomly arriving email

Example: Gambling is often maintained by a variable ratio schedule, which is highly resistant to extinction.

Relevant Equations

• Learning Rate Equation: $\text{Rate} = k[\text{Reinforcer}]$ Additional info: This equation is a simplified representation; actual learning rates depend on schedule and context.

Additional info: Dopamine pathways in the brain (e.g., nucleus accumbens and ventral tegmental area) are involved in reinforcement learning, influencing motivation and reward.