Learning- Test 1

Learning can be…

1. The acquisition of new behaviors:

• learning to drive a car

1. A change in the frequency of previous behaviors:

• a rat learning the more they press a lever, the more food they get

Learning theory is rooted in…

philosophy

Descartes

• Pre-descartes, all human behavior was considered free will

• Descartes observed many behaviors involuntary

• Unable to abandon free will, he maintained some behaviors were voluntary

~Thus, DUALISM

Reflex

involuntary behaviors that consist of automatic reactions to external stimuli

• Sensory input is “reflected” in the response (Reflex Arc)

• Descartes suggested that most behaviors are mental reflexes

  • Stimulus in, action out

Descartes reflex arc

**new items= nerves & brain

• Stimuli that affects sense organs

• Using nerves (“tube filled with animal spirits”) message is sent to the brain

• The pineal gland → mind

  • Innately human

• Sent back through the same tubes to form a reaction

Reflexes and free will

• Involuntary human and all human behaviors→  reflexes

• Voluntary human behaviors → free will

Nativism

a philosophical approach that we are born with innate ideas about certain things

John Locke

• Took umbrage with “free will.”

  • No such thing as free will

• Believed all ideas were acquired through experience after birth 

  • (Tabula Rasa- clean slate)

Thomas Hobbes

• Accepted voluntary vs involuntary, but believed that the mind operated predictably

• Hedonism- the pursuit of pleasure and the avoidance of pain

Empircism

• Empiricists believed all ideas originate from sense experience

• Complex ideas form as simple sensations combine by associations (ex. BURRITO)

• “Rules of associations” were proposed by Aristotle 2000+ years ago

Contiguity

 If 2 events (things) repeatedly occur together in time or space, they will become associated

• Example: snow and winter

**Has received the most attention and support

Similarity

 2 events (things) will become associated if they are similar in some respect

• Example: color (red & blue)

Contrast

2 events (things) will become associated if they are different in some characteristic.

• Example: salt and pepper

Rules of association

1. contiguity

2. similarity

3. contrast

Research dispelled some misconceptions of Descartes’ reflex arc:

• Sensory and motor nerves aren’t the same

• The Pineal gland is NOT central to learning

• Even reflexes are modifiable with experience

Sechenov

• “Even a small particle of dust could elicit a tremendous sneeze.”

• Complex behaviors can be formed by subconscious stimuli

• Believed no behavior was truly voluntary

Pavlov

• Demonstrated not all reflexes are innate

• Strong associations can create  new and lasting behavior

  • Nervism- all key physiological functions are governed by the nervous system

Charles Darwin

Expanded upon species overlap (emphasized commonalities of species)

• Not a large division between human & animals behavior

• Not true that animals can perform only involuntary behavior and humans can only perform voluntary behavior

  • Proposed evolution of physical and mental traits

What is intelligence?

Romanes- the ability “to make adjustments, or modify old ones, in accordance with the results of its own individual experience.”

• Basically, in sum the ability to learn

How does the brain learn?

Functional neurology- key behavioral functions are governed by the nervous system

• “All behavior is a reflection of brain function.”

  • Morris water maze

  • Long-term potentiation

Dollard & Miller

• “We are working on the hypothesis that people have all the learning capacity of rats.”

  • Ex. taste aversion, maze learning

• The assumption is probably true in most cases, but a rat would never drink Jose Cuervo again after getting sick

• Animal models should be relevant to human behavior (i.e., face validity)

Benefits of animal models

• Simplicity

• Controlled

• Cost effective

• Mechanistic

Dangers of animal models

• Overgeneralization 

  • Rats don’t really have a prefrontal cortex (different brain structures)

• Inappropriate model

• Unwarranted application

Formal definition of learning

Learning- an enduring change in the mechanisms of behavior involving specific stimuli and/or responses that result from prior experience with those or similar stimuli and responses

Enduring

– Some changes in behavior are too brief to be learning…

• Fatigue

  • Exhaustion is not learning

  • The decline in responding disappears if the person rests for a while

• Change in stimulus conditions

  • An abrupt change in conditions may alter behavior

    • Ex. lights randomly go off during a movie- response to a change in the environment

• Altered motivational scale

  • Estrous cycle may temporarily change behavior

Mechanisms of behavior

–Learning is NOT a change in an organism’s actions at one time or a performance

• Subject to alteration by opportunity and motivation 

  • Ex. singing in the shower vs in front of a group

• Mechanisms of behavior can be determined only with control groups across time

Prior experience

Enduring changes may occur without prior experience

• Ex. changes due to maturation are not learning

  • Maturation occurs in the absence of training or practice

    • Rooting reflex- disappears in development as the child matures (not learning)

—This can be tricky because maturation & learning often co-occur

Causal mechanisms of learning

1. efficient cause

2. material cause

3. formal cause

4. final cause

Efficient cause

the training procedure with specific stimuli and response that cause a behavioral change

• The stimulus (context), behavior (lever pressing), pellets/water (reinforcer) can cause a change in behavior

Material cause

physical changes in the brain that mediate learning

• Biological processes that underlie learning

• Ex. Rat swimming in water maze (hippocampus has encoded the room)

Formal cause

 theories of learning at the behavioral level

• Allows us to understand the change in behavior as a result of the variables across species; can make predictions about behaviors

Final cause

evolutionary mechanisms that contribute to the organism’s reproductive fitness

• With rats, it only takes one taste aversion experience and they will never eat something again in their life

Stimulus

an agent, action, or condition that elicits a physiological or psychological response

• Examples- Mosquito bite, close encounter with a shark, a burrito

Response

a unit of behavior; a discrete and usually recurring segment of behavior

• Examples- itch, heart rate, salivation

Elicited behavior

behavior that occurs in response to specific environmental stimuli

reflexes

• Simplist form of behavior

  • Knee tap— kick

  • Loud noise—-startle

• Anatomically specific, can be modified by the brain

• Can change with development…

  • Grasping 

  • Rooting reflex

Modal action patterns

 complex, species-specific response sequences

ex. herring gull beak

Important characteristics of MAPs:

1. Often unique to a species

2. All species members show the behavior

3. Not the result of prior learning

4. Behavior occurs in a rigid order

5. Triggered by a specific stimulus (sign stimulus)

Sign stimulus

The specific features required to elicit a MAP

Supernormal stimulus

An unusually effective sign stimulus based on preferred properties

• for humans: ads/marketing

Appetitive behavior

• Early part of the sequence

• Behaviorally flexible

• Easy to modify

Examples:

• Searching for food

• Looking for a (or to) mate 

Consummatory behavior

• End component of the sequence

• Often species-specific

• Difficult to alter

Examples:

• Feeding young 

  • Feeding occurs in pretty much the same way for each species

• Preparing a nest

Habituation

(decreased) response with repeated stimulation

Sensitization

(increased) response with repeated stimulation

Why habituate/sensitize?

To organize and focus behaviors based on stimulus relevance

• Allows us to adapt and survive 

Habituation is stimulus-specific

• Altering the stimulus elicits the habituated response

• Rules out muscle fatigue

  • Example: switching tone quality restores startle

  • Lemon/lime example

Habituation is response-specific

• Reduced responding to stimulus in one aspect of behavior but not others

• Rules out sensory adaptation 

  • Example: a child may still listen despite reduced eye contact

Sensitization can only be ruled out by what?

electrophysiological tests

Dual process theory

—Formal cause

• Two distinct neural processes:

  • Habituation process 

  • Sensitization process

• These processes act simultaneously

• The behavioral outcome (performance) depends upon the strength of each process (net sum)

Stimulus-response (S-R) system:

 habituation occurs in the reflex arc

• Specific stimulus and response

• Short neural loop

• Each stimulus presentation activates the loop

State system

sensitization occurs in CNS areas that determine activation

• Generalized response

• Only activated during arousing events

• Psychoactive drugs can affect the state system

Davis, 1974 (background noise)

–How would dual process theory explain Davis' study

• Response to tone decreases w/ soft background

• Response to tone increases w/loud background

• Change in 20 db, amplified state system

  • Sensitization processes become more dominant than habituation

Habituation - time course

• Semi-permanent

• Determined by stimulus interval

  • Short-term habituation: when stimulus is frequent

  • Long-term habituation: when stimulus is widely spaced

Sensitization- time course

• Temporary

  • Ex. 15 min. After 80 db background is off in Davis (1974), rats startle returns to baseline

• Determined by stimulus intensity

Spontaneous recovery

partial restoration of response with the same stimulus after time has passed

Habituation- stimulus-specificity

• Stimulus-specific

  • Changing taste reinstates responding

• Stimulus generalization

  • Sufficiently similar stimuli may generalize (ex. Sprite- Sierra Mist)

Sensitization- stimulus-specificity

• Not stimulus specific

• Animal will readily generalize to other cues in environment

• Reflects final cause

Dishabituation

• Habituation can be reversed by a change in stimulus features

  • Ex. lime, lime, lime, lemon

• Dishabituation- restoration of response by a strong, extraneous, surprising stimulus

  • Dishabituation is a result of state system activation

Aplysia

studying the MATERIAL CAUSE of learning

Habituation/sensitization reflect changes in CNS neurotransmitter release from….

Sensory » motor neuron

• Habituation: repeated skin stimulation ↓ SN neurotransmitter release in CNS, which ↓ MN response

• Sensitization: tail shock activates excitatory facilitatory neuron (FN) and ↑  SN neurotransmitter release in CNS to ↑  MN response

Habituation and sensitization can be applied to Biphasic emotional reactions to drugs

• Heroin:

  • Early: relaxed, euphoric

  • Late: irritable, depressed

Opponent process theory

 mechanisms that control emotional behavior minimize deviations from emotional neutrality (homeostasis)

Primary process (a)

• elicited directly by an arousing stimulus (it is efficient)

  • Heroin elicits euphoria immediately

Opponent process (b)

• elicited indirectly by the primary process (it is initially inefficient)

  • Euphoria elicits depression, which is delayed

Repeated exposure to drug x

• First drug experiences are often highly pleasurable, with minor aversive after-effects

• Addiction reflects attempts to reduce aversive after-effects (withdrawal), without initial pleasure (tolerance)

  • With repeated exposure, (b) processes become more efficient

Classical conditioning is more complex…

• Organisms learn associations between stimuli

• New responses are learned

Edwin B. Twitmyer

• Rang bell– hit knee

• Over time, the bell alone began to elicit knee-jerk

Ivan Pavlov

• Dogs increased stomach juices with the sight of food

• “Psychic juices” sold to the public 

Modern classical conditioning tests

• Fear conditioning

• Eyeblink conditioning

• Sign tracking (autoshaping)

• Taste aversion 

Fear conditioning

—pairing of a tone with a shock

• Freezing is a primary defensive response

• When presented tone or light they freeze, even without shock

Conditioned suppression procedure

• Acquisition- rats are trained to press lever for food

• Conditioning:

  • CS: tone

  • US: shock after tone

  • UR: rats freeze

    • Shock suppresses lever pressing

  • CR: rats freeze

    • The tone suppresses lever pressing

• Once the CS is learned, once tone is off, lever pressing re-starts

Suppression ratio

(S.R.)= A/ (A + B) 

• A= response during 2-min. CS

• B= response prior to the 2-min. CS

What does a low suppression ratio number mean?

strong suppression; lots of fear

Eyeblink conditioning

—a component of “starte”

• US: air puff at eyes

• UR: eyeblink

• CS: tone

• CR: eyeblink

  • Useful to study neurological substrates of learning

Sign tracking (autoshaping)

movement towards a stimulus signaling availability of a positive reinforcer (food, reproduction)

Brown & Jenkins

• Food-deprived pigeons for training

• Birds exposed to a “key” light 8 sec before food

• Predicted birds would see the light then go to the food cup

• Found that instead birds vigorously pecked the light

Hearst & Jenkins (Long box)

• Paired light (CS) with food (US; available only 4 sec.)

• Pigeons pecked the light as soon as it came on

• As soon as the light turned off, pigeons rushed to the food

Taste aversion

 learned aversion to a novel flavor if followed by illness

Taste preference

learned preference to a flavor paired with nutrient replenishment

• Ex. gatorade can produce a strong taste preference post-workout

What can taste aversion occur from…

• Food poisoning

• Chemotherapy

• Allergies 

Taste aversion procedure (saccharin)

• Intervals between CS (taste) and US (x-ray)

  • 0-6 hours- profound taste aversion

  • 6-12 hours- moderate taste aversion

  • 12-24 hours- mild to no taste aversion

• Rats learning the aversion maintain it for life

• Rats who did not, still show saccharin preference (~80%)

Excitatory classical conditioning

The organism learns associations between the CS and US and anticipates the presence of the US

Conditioning trial

 Single trial w/ 1 US and 1 CS

Training session

A series of conditioning trials

Intertrial interval

The end of 1 trial to the start of the next

Interstimulus interval

Time from start of CS to the start of the US

short delayed (excitatory training)

• Short ISI

• CS and US overlap

Trace (excitatory training)

• Larger ISI

• No overlap (trace interval)

Long-delayed (excitatory training)

• Large ISI

• Overlap btw CS and US

Simultaneous (excitatory training)

• No ISI

• Total overlap

Backward (excitatory training)

US precede CS

Random control (GOOD)- classical conditioning

• CS and US occur randomly in same trial

• Can still produce learning

Explicitly unpaired control (BEST)- classical conditioning

• US and CS presented on different trials

• Far apart to prevent associations

• How far depends upon the procedure

  • Example: eyeblink vs taste aversion

Which conditions produce the strongest learning?

Interstimulus interval

• Timing of CS and US onset is key

Conditioning is best when CS predicts the US will occur soon

• Best: short delay

• Worst: simultaneous

Temporal coding hypothesis

The organism learns not only the CS-US association, but when stimuli occur

Inhibitory classical conditioning

The organism learns associations between the CS and US, which predicts the absence of a US

Reasons for inhibition

• Unpredictable aversive stimuli are stressful

• We seek periods of low risk

• We are built to predict the absence of an event

  • Likelihood of no pain

  • Likelihood of no pleasure

Prerequisite for inhibitory conditioning

For the absence of the US to create CS- learning, the US must occur periodically

• Example: for a rainbow to predict end of rain, it must occasionally rain

Two basic procedures for inhibitory conditioning

1. standard procedure

2. negative contingency