PSYC2081 Notes: Introduction, Pavlov & Skinner

Course context and structure

  • PSYC2081: Learning and Physiological Psychology
  • Topic: Introduction, Pavlovian (classical) conditioning and Skinnerian (instrumental/operant) conditioning
  • Course logistics (from the transcript):
    • Assessments: mid-term exam 15\%, weekly activities 5\%, research report 40\%, final exam 40\%
    • Read the course outline on Moodle for all required information
    • Core text reference: Pearce, J. M. (Animal Learning and Cognition), Chapters 1–4
  • Lecturers include Dr. Nathan Holmes and a team of four other lecturers/tutors
  • Foundational idea: learning as a process by which organisms adapt to their environments by using the past to predict the future and act in the present

Todays lecture overview

  • Learning as adaptation: organisms use past experiences to predict future events and guide present behavior
  • Introduction to Pavlovian (classical) conditioning
  • Introduction to instrumental (operant) conditioning
  • Emphasis on two types of learning:
    • How we learn about relationships between stimuli or events in the world
    • How we learn about the relationship between our actions and stimuli/events

Two types of learning (foundational distinction)

  • Type 1: How we learn about relationships between stimuli/events in the world
    • Why we are attracted to some stimuli/objects/events and repelled by others
  • Type 2: How we learn about the relationship between our actions and stimuli/objects/events
    • How actions influence subsequent stimuli or events

Pavlovian/classical conditioning: core ideas

  • Classical conditioning involves learning that a neutral stimulus signals the arrival of a biologically relevant event (the US)
  • In Pavlov’s terms:
    • Unconditioned Stimulus (US): elicits a natural, unlearned response (UR)
    • Unconditioned Response (UR): natural response to the US
    • Conditioned Stimulus (CS): originally neutral stimulus that acquires the ability to signal the US
    • Conditioned Response (CR): learned response to the CS
  • Pavlov’s discovery: dogs salivated not only to food (US) but also to signals associated with food (e.g., bell, attendant) that predicted food
  • Anticipatory salivation vs. salivation to food in the mouth: anticipatory salivation is a learned response to cues predicting food, whereas salivation to the food itself is a physiological reflex
  • Key principle: the CS must be paired with the US for learning to occur; the dog does not need to salivate to obtain the food (the US occurs irrespective of the CR)
  • Crucial generalization: a CS from any sensory modality can become associated with a US (visual, tactile, olfactory, interoceptive cues)
  • Temporal relation: CS precedes US (often briefly); the association strengthens as the CS reliably predicts the US

Pavlov’s apparatus and paradigm (historical details)

  • Apparatus: fistula implanted in the dog’s mouth to collect salivation; dog’s salivation recorded while food is delivered
  • Setup allowed manipulation of stimuli (e.g., a bell or other signal) preceding the food delivery
  • Central finding: learning occurs when a neutral cue signals food, leading to salivation in anticipation of the food
  • Interpretation: anticipatory salivation reflects a mental state of affairs (the thought or expectation of food), distinct from reflexive saliva to actual food
  • Importance: demonstrated that learning transfers control over a physiological reflex from the US to a predictive cue (the CS)

Pavlov’s learning phenomena (classical conditioning dynamics)

  • External inhibition: salivation decreases when the CS is paired with a novel stimulus (e.g., light) that diverts attention away from the CS; strong CR when CS alone, weaker when CS is paired with a novel stimulus
  • Extinction: gradual reduction and eventual elimination of the CR when the CS is repeatedly presented without the US
  • Disinhibition: the extinguished CR reappears when the extinguished CS is presented together with a novel stimulus; attention to the novel stimulus temporarily reduces the inhibition of the CS-CR link
  • Spontaneous recovery: after extinction, the CR can reappear when the CS is presented after a delay (days or weeks)
  • Summary conceptualization: a CS can become associated with a US, producing a CR; several dynamics (extinction, disinhibition, spontaneous recovery, external inhibition) modulate the strength and expression of the CR

Pavlovian conditioning: cross-modal generality and implications

  • Stimuli from all five sensory modalities can serve as CSs
  • The CRs can be externally inhibited or extinguished depending on CS context and US availability
  • Extinction does not erase the original learning; rather, it involves new learning that inhibits the CR, which can re-emerge under certain conditions (disinhibition or spontaneous recovery)
  • Practical takeaway: classical conditioning explains how environmental cues become predictive of important events and how context and novelty can shape responses

Pavlovian conditioning: key statements and quotes from the lecture materials

  • “The originally neutral conditioned stimulus (CS), through repeated pairing with the unconditioned stimulus (US), acquires the response originally given to the unconditioned stimulus.”
  • “Stimuli from all five sensory modalities can be conditioned.”
  • “External inhibition, extinction, disinhibition, and spontaneous recovery” are core phenomena observed in classical conditioning
  • “Anticipatory salivation is a response to a mental state of affairs (the thought of food)”

Foundational individuals and studies in classical conditioning

  • Watson & Raynor (1920): The case of Little Albert (early human conditioning example)
  • Ivan Pavlov (1849–1936): Russian physiologist; Nobel Prize in Medicine for digestion studies; introduced conditioned reflexes; published Conditioned Reflexes (1927)
  • Key idea: conditioning shifts control of reflexive responses from the US to CS via association learning

Skinner and instrumental conditioning (operant conditioning)

  • Burrhus Frederic Skinner (1904–1990): influential figure; Harvard professor; studied instrumental (operant) conditioning using the “Skinner Box” to automate scheduling of events and responses
  • Experimental setup (illustrated in the lecture): a rat in a Skinner box could press a lever to obtain food; the action (lever press) is instrumental in obtaining the reward
  • Core distinction from Pavlov: in operant conditioning, the organism’s behavior (e.g., lever pressing) is emitted to obtain a consequence; the response is not elicited automatically by a CS but strengthened or weakened by consequences
  • Crucial terminology: reinforcement and punishment govern the likelihood of the preceding behavior

Reinforcement and punishment: basic concepts (Skinner)

  • Reinforcer definition: anything that increases the likelihood of the immediately preceding behavior (i.e., strengthens the contingent response)
  • Schedules of reinforcement: the relationship between reinforcement and behavior over time
  • Partial (intermittent) reinforcement is more effective for maintaining behavior than continuous reinforcement

Schedules of reinforcement: key types

  • Fixed Ratio (FR_n): reinforcement after n responses
    • Example: a worker paid for every n units produced
    • Characteristic: rapid response with a post-reinforcement pause; the pause length is proportional to the number of responses required
  • Variable Ratio (VR_n): reinforcement after an average of n responses
    • Example: fishing (reward after a variable number of casts); leads to high and steady response rates with little post-reinforcement pause
  • Fixed Interval (FI_t): reinforcement after a fixed period of time
    • Example: exams or other timely contingencies; response rate tends to rise near the time of reinforcement
  • Variable Interval (VI_t): reinforcement at variable time intervals
    • Example: checking emails; responses tend to be steady and moderate

Characteristics and practical illustrations

  • Ratio schedules tend to produce rapid responding
  • FRn leads to post-reinforcement pauses; the pause length increases with n
  • VRn yields high, steady rates of responding with little to no post-reinforcement pause
  • VI and FI schedules produce more steady behavior than fixed-ratio schedules but with different temporal dynamics
  • Real-world analogies:
    • Fruit picker paid by number of baskets filled (FR-like)
    • Fishing: rewards occur after variable numbers of casts (VR-like)
    • Checking email: variable-interval-like reinforcement

Instrumental conditioning procedures and contingencies

  • Reinforcement vs punishment framework (operant contingencies)
    • Positive Reinforcement: a behavior produces a desirable outcome
    • Negative Reinforcement: a behavior prevents an aversive outcome
    • Punishment: a behavior produces an aversive outcome
    • Omission training (negative punishment): a behavior prevents a desirable outcome
  • These contingencies shape the likelihood of the target behavior across time

Comparison: Pavlov vs. Skinner (the interpretive contrast)

  • Pavlovian conditioning (Classical): CS signaling the US elicits a reflexive CR; learning is about forming associations between stimuli
  • Instrumental conditioning (Operant): the organism’s response leads to consequences; learning is about the relationship between actions and outcomes; behavior is emitted and shaped by consequences
  • In Pavlovian conditioning, the CR is elicited by the CS; in operant conditioning, the behavior is emitted to obtain reinforcement

Ethical, philosophical, and practical implications

  • Real-world and clinical contexts raise ethical considerations:
    • Classic human conditioning experiments (e.g., Little Albert) highlighted ethical concerns about harm and consent
    • Modern research emphasizes welfare and ethical guidelines for animal and human subjects
  • The Ludovico Technique (fictional but discussed in lecture materials): a memory- and behavior-control procedure that subjects individuals to violent stimuli under drug-induced sickness to condition aversions; raises questions about autonomy, consent, and the potential for abuse in behavioral modification
  • Hijacking (memory alteration for torture): Tracker jacker venom used to associate fear with memories and to alter those memories with hallucinations; highlights risks of memory manipulation and the ethics of coercive applications
  • Real-world relevance: conditioning principles underpin advertising, education, habit formation, and behavior modification programs; ethical use requires careful consideration of autonomy, welfare, and potential harms
  • Foundational principles connect to broader debates in philosophy of mind and ethics about mental states, agency, and the limits of behavioral control

Key definitions and shorthand references (summary)

  • US: Unconditioned Stimulus — naturally elicits a response (e.g., food)
  • UR: Unconditioned Response — natural, reflexive response to the US
  • CS: Conditioned Stimulus — originally neutral, becomes predictive of the US
  • CR: Conditioned Response — learned response to the CS
  • FI_t: Fixed Interval schedule (time-based reinforcement at fixed intervals)
  • VI_t: Variable Interval schedule (time-based reinforcement at variable intervals)
  • FR_n: Fixed Ratio schedule (reinforcement after a fixed number n of responses)
  • VR_n: Variable Ratio schedule (reinforcement after an average of n responses)
  • Positive Reinforcement: R -> addition of a desirable outcome
  • Negative Reinforcement: R -> removal of an aversive outcome
  • Punishment: R -> introduction of an aversive outcome
  • Omission training: R -> removal of a desirable outcome
  • Extinction: CS on its own presented without US leads to decrease in CR
  • Spontaneous recovery: CR reappears after time without exposure to CS
  • Disinhibition: CR reappears when a novel stimulus is introduced during extinction
  • External inhibition: a novel stimulus reduces CR expression when paired with CS

References and context from the lecture slides

  • Pavlov (1849–1936): classical conditioning pioneer; Nobel laureate in physiology; early work on digestion and conditioned reflexes; Conditioned Reflexes (1927)
  • Watson & Raynor (1920): Little Albert study (human conditioning example)
  • Skinner (1904–1990): operant conditioning pioneer; Skinner box; reinforcement schedules; focus on action-outcome contingencies
  • Pearce, J. M. (Year not specified in notes): Animal Learning and Cognition, Chapters 1–4
  • Notable additional examples in lecture: The Ludovico Technique and Tracker jacker memory manipulation as ethical/practical concerns in learning and memory research

End-of-lecture takeaway

  • The course integrates two complementary learning theories: classical conditioning (Pavlov) and operant conditioning (Skinner)
  • Both frameworks explain how organisms adapt their behavior based on environmental contingencies, with broad implications for psychology, education, marketing, and ethics