PSYCH EXAM 2

Brain and Language Processing

Left Hemisphere Brain Lesions

• Can result in:

  • Essential apraxia (from frontal lesion)

  • Agnosia (from back lesion of language)

  • Expressive aphasia – Inability to produce speech

• Broca’s Area (Frontal Association Area)

  • Lesions here lead to speech production issues

  • Controls motor projection areas for speech: throat, tongue, jaw, lips

  • Related to general language capacity

Split-Brain Studies

• Corpus Callosum Severance

  • Done to reduce severity of seizures

  • Leaves patient mostly normal but creates subtle independence between left and right brain

Visual Pathways

• Left side of each eye sends information to left hemisphere

• Right side of each eye sends information to right hemisphere

• Result:

  • Left visual field → Right hemisphere

  • Right visual field → Left hemisphere

  • Called contralateral organization

Experiment on Split-Brain Patients

• Setup:

  • Patient looks straight ahead

  • Picture is flashed faster than the eye can move

  • Asked, “What did you see?”

• Results:

  • Cup on right → Left hemisphere says “cup”

  • Spoon on left → Left hemisphere says nothing

  • When told to reach for the object with the left hand, the right hemisphere grabs the spoon

  • If asked what it is, the left hemisphere guesses (e.g., "pencil"), and the right hemisphere may frown

Key Takeaways

• Left hemisphere = Language processing

• Right hemisphere = No language, but can recognize objects

Classical Conditioning (Pavlov’s Experiments)

• US (Unconditioned Stimulus) → Input to a reflex (e.g., food in mouth)

• UR (Unconditioned Response) → Output of reflex (e.g., salivation)

• CS (Conditioned Stimulus) → Initially causes investigatory response, then habituation (e.g., bell)

• CR (Conditioned Response) → Learned response to CS (e.g., salivation to bell)

Pavlov's Findings

• Psychic Reflex: Dog perceives something and responds

• Conditioned Reflex: A learned reflex (CS before US)

• Strength of Conditioned Response

  • Measured by: Amplitude, Probability, Latency

  • Example: Rabbit conditioned to fear a tone (CS) due to an electric shock (US)

Growth of Conditioned Response

• Acquisition Phase:

  • Strength of CR increases with reinforced trials (CS + US)

  • Growth rate flattens out when max response is reached (e.g., dog does not have infinite saliva)

• Extinction:

  • CR declines and disappears over trials when US is not presented (e.g., bell without food)

  • Due to buildup of inhibition

• Spontaneous Recovery:

  • After a rest interval (e.g., 24 hours), CR reappears at almost previous strength but weakens faster

  • Due to dissipation of inhibition

Excitatory and Inhibitory Associations

• Once a conditioned response is learned, it is never forgotten

• Extinction does not erase learning but creates a competing inhibitory association

  • Dog learns:

    • Bell → Food (excitatory)

    • Bell → No food (inhibitory)

  • After rest, the dog balances between the two, leading to a weaker CR

Classical Conditioning

• Involuntary responses involved

• Contiguity: Closeness in time is the basis of acquisition of a conditioned reflex

• Optimal Time Interval:

  • Differs depending on response being conditioned

    • Dog’s salivation response: 5-30 sec

    • Human eyeblink response: 0.5 sec

  • Number of trials required for conditioning varies

• Stronger CS = Stronger CR

  • Example: Louder tone, brighter light → More salivation

Higher-Order Conditioning (Second-Order Conditioning)

1. Establish CS → (e.g., Bell → Salivation)

2. Pair a new CS with the old CS, without the US → (e.g., Tone → Bell → Salivation)

3. Eventually, the new CS produces CR without US → (e.g., Tone → Salivation)

• US acts as a reinforcer for the conditioned reflex

• In higher-order conditioning, a CS acts like a US (secondary reinforcer)

• Classical conditioning is more versatile – It can happen even in the absence of an unconditioned stimulus

Extinction & Generalization

• Extinction: Presenting a CS without a US leads to a decline in CR

• Generalization:

  • Similar stimuli produce similar responses (e.g., petting both dogs and cats)

  • Example: A different pitch tone still produces salivation

• Discrimination:

  • Learning to differentiate between stimuli

  • Example: Training “CS+” (high tone with US) and “CS-” (low tone without US) → CR only to CS+

CR vs. UR

• CR ≠ UR

• CR may be a preparatory response for US

  • Example:

    • CS (Tone) → US (Shock) → UR (Fast heartbeat, heavy breathing)

    • CS (Tone) alone → CR (Slower heartbeat, breathing)

  • Example:

    • CS (Injection) → US (Morphine) → UR (Less pain)

    • CS (Injection) alone → CR (More pain sensitivity)

What Gets Learned?

• Pavlov’s View: CS-CR (Conditioned Reflex)

• Modern View: CS-US Association → CS provides information about US

• Backward Conditioning (US before CS) fails

Split-Brain Studies

• Corpus Callosum Severance:

  • Done to reduce seizures

  • Minimal effect on daily life

• Visual Pathways:

  • Right eye → Left hemisphere

  • Left eye → Right hemisphere

Operant (Instrumental) Conditioning

• Developed by Edward Thorndike (1898)

• Trial-and-error learning

• Law of Effect:

  • Behavior is strengthened when followed by reinforcement (“satisfying state of affairs”)

  • Behavior is weakened when followed by punishment (“annoying state of affairs”)

Thorndike’s Puzzle Box (Cat Experiment)

• Studied animal problem-solving

• Reinforcement strengthens response

• Insight: Sudden grasp of a problem’s structure

• Wolfgang Köhler (1914): Experimented with chimpanzees to test insight learning

Operant vs. Classical Conditioning

• 
  Delay of reinforcement weakens response

• Operant Conditioning Example:

  • Rat presses a bar in a Skinner Box → Reinforcement strengthens bar-pressing behavior

• Terminology:

  • Emitted Response: Spontaneously produced behavior (Operant Conditioning)

  • Elicited Response: Experimenter controls response (Classical Conditioning)

Key Concepts

• Contingency: Dependency between behavior and reinforcement

• Contiguity: Closeness in time makes learning happen

Operant Conditioning - B.F. Skinner & The Skinner Box

Basic Principles

• Many responses can be made with little time and effort.

• Responses are easily recorded and response rate is the preferred dependent variable (measured by the slope of a cumulative record).

• Cumulative record: Graph showing responses over time.

  • Example: 30 responses in 5 minutes = 6 responses per minute.

  • Extinction: Represented by a flat, straight line (unlike classical conditioning).

• Common test subjects: Rats and pigeons.

Reinforcement & Punishment

Reinforcement always increases behavior (both positive and negative).

• Positive reinforcement: Adds an appetitive stimulus (e.g., food, approval).

• Negative reinforcement: Removes an aversive stimulus (e.g., shock, alarms, clock noise).

  • Example: An alarm clock removes an aversive stimulus when turned off.

Punishment decreases behavior

• Positive punishment: Adds an aversive stimulus (e.g., shock when a response is made).

• Negative punishment: Removes a desirable stimulus (e.g., taking away a toy from a child).

Extinction & Spontaneous Recovery

• Extinction: When reinforcement is removed, the response stops.

• Spontaneous recovery: A previously extinguished response reappears after a delay.

Discriminative Stimulus & Operant Conditioning

• Discriminative stimulus: Signals under what conditions a response will be reinforced.

  • Example: A rat presses a bar but only gets food when a light is on → eventually, it only presses when the light is on.

  • The stimulus does not cause the response or reinforcement; it sets the occasion for the response.

  • Parallel to classical conditioning:

    • Instead of a conditioned response (CR) → operant response

    • Instead of an unconditioned stimulus (US) → reinforcement

    • Instead of a conditioned stimulus (CS) → discriminative stimulus

  • Order Difference:

    • Classical Conditioning: Stimulus (CS) → Reinforcement (US) → Response (CR)

    • Operant Conditioning: Stimulus → Response → Reinforcement

Conditioned (Secondary) Reinforcers

• A stimulus that gains reinforcing properties through classical conditioning.

  • Example: A clicker for training dogs → initially paired with food → eventually reinforces behavior on its own.

Schedules of Reinforcement

Continuous Reinforcement (CR)

• Every response is reinforced.

Partial Reinforcement Effect

• Reinforcing only some responses produces stronger responding than reinforcing all responses.

Types of Partial Reinforcement:

1. Interval Schedules (Reinforcement based on time)

   • Fixed Interval (FI): Reinforcement occurs after a fixed time interval (e.g., checking mail at a set time each day).

   • Variable Interval (VI): Reinforcement occurs after an unpredictable time interval (e.g., checking email, which is delivered at random times).

   • Predictability affects behavior—fixed intervals lead to responses closer to expected reinforcement time.

2. Ratio Schedules (Reinforcement based on number of responses)

   • Fixed Ratio (FR): Reinforcement after a set number of responses (e.g., factory workers paid per item produced).

   • Variable Ratio (VR): Reinforcement after an average number of responses (e.g., gambling, where payouts are unpredictable).

Shaping & Chaining

• Shaping: Reinforcing successive approximations of a behavior to gradually guide toward a desired response.

  • Example: Training an animal to press a lever by reinforcing behaviors that get closer to the goal.

• Chaining: Linking multiple responses into a sequence to train complex behaviors.

  • Example: Teaching a dog to fetch by reinforcing picking up the toy, bringing it back, and dropping it in order.