Learning is a phenomenon in which behavior changes through experience and the change persists for a relatively long time. Learning includes many types, from habituation to complex problem solving. Let us understand the findings of experimental psychology, known for Pavlov's dogs and Skinner's box, together with their evolutionary and ecological contexts.
Basic Knowledge
Habituation: The simplest form of learning, in which the response to a repeatedly presented harmless stimulus gradually weakens. Example: An animal is startled by a sudden sound, but its response becomes weaker when the sound is repeated. Adaptive significance: reducing the cost of responding to unnecessary stimuli.
Imprinting: Discovered by Lorenz. Learning in which an individual is permanently influenced by a specific stimulus during the sensitive period (critical period) early in life. Example: Herring gull chicks follow the first moving object they see as their parent within several hours after hatching. Reverse imprinting does not occur (unidirectionality and irreversibility). Sexual imprinting, which affects mate choice, is also important.
Classical conditioning (Pavlovian conditioning): When a conditioned stimulus (CS) (bell sound) is repeatedly presented before a pair of unconditioned stimulus (UCS) (food) → unconditioned response (UCR) (salivation), the CS alone comes to produce a conditioned response (CR) (salivation). This is stimulus–stimulus associative learning. Extinction = the CR weakens when the CS is repeatedly presented alone. Spontaneous recovery, generalization, and discrimination are also important concepts.
Operant conditioning (instrumental conditioning / Skinnerian conditioning): Associative learning between a voluntary behavior and its consequence. Positive reinforcement = a reward is given after a behavior → the frequency of the behavior increases. Negative reinforcement = an aversive stimulus is removed → the frequency of the behavior increases. Punishment = an aversive stimulus is given → the frequency of the behavior decreases. Resistance to extinction differs according to the reinforcement schedule (continuous or partial reinforcement).
Compare classical conditioning and operant conditioning using Pavlov's dogs and Skinner's box as examples.
Answer: Classical conditioning (Pavlov): An unconditioned stimulus (food) and a conditioned stimulus (bell) are presented together. The animal is passive and associates an existing reflex response (salivation) with a new stimulus. It is automatic “stimulus → response” associative learning. Operant conditioning (Skinner): A rat presses a lever (voluntary behavior), and food is delivered (reinforcer). The animal actively acts on the environment. It is “behavior → consequence” learning in which the frequency of a behavior changes according to its consequence.
- Habituation = weakened response to a repeated harmless stimulus; the simplest form
- Imprinting = sensitive period, unidirectional, irreversible, and associated with Lorenz
- Classical conditioning = UCS + CS → CR (stimulus–stimulus association)
- Operant conditioning = voluntary behavior + reinforcer (behavior–consequence association)
- Positive reinforcement = providing a reward → increased behavior
- Extinction = the conditioned response weakens when the conditioned stimulus alone is repeatedly presented
- Sensitive period = a limited period during which a particular type of learning is likely to occur
Points to Note
① “Negative reinforcement” is not punishment. It means increasing a behavior by removing an aversive stimulus. ② Imprinting is limited to the sensitive period, and differs from other learning because it is difficult to change once established. ③ Habituation differs from fatigue and sensory adaptation (the response recovers when an appropriate stimulus is presented).
Practice
- Explain the characteristics of imprinting using the terms “sensitive period” and “irreversibility.”
- State the unconditioned stimulus, conditioned stimulus, and conditioned response in Pavlov's experiment.
- Explain the difference between positive reinforcement and negative reinforcement in operant conditioning, giving examples.