Chapter 6
Learning and Behavior
Learning
A more or less permanent change in behavior that results from experience
Behavior
The ways in which animals act or respond in an environment– influenced by both biological and learned
components
Richard Dawkins: Memes
A cultural invention that is passed on from one generation to the next
Marvin Harris (1974)– “Our primary mode of biological adaptation
is cultural not anatomical”
Ivan Pavlov
Learning is an associative process– Pavlov studied a learned association
between a neutral stimulus and a reflexive response
Classical Conditioning
US - Unconditioned Stimulus– stimulus that evokes the behavioral response of
interest (Meat powder) UR - Unconditioned Response
– the reflexive response to the presentation of the US (Salivation)
NS - Neutral Stimulus– a stimulus that does not result in an
unconditioned response (Bell)
Classical Conditioning
NS (Bell)No UR (No Salivation)
Before Conditioning
produces
produces
Classical Conditioning
Before Conditioning
NS (Bell)No UR (No Salivation)produces
produces
US (Meat) UR (Salivation)produces
produces
Classical Conditioning
NS (Bell)+
US (Meat) UR (Salivation)
During Conditioning
produces
produces
+
Trial 1
Classical Conditioning
NS (Bell)+
US (Meat) UR (Salivation)
During Conditioning
produces
produces
+
Trial 2
Classical Conditioning
NS (Bell)+
US (Meat) UR (Salivation)
During Conditioning
produces
produces
+
Trial 3
Classical Conditioning
NS (Bell)+
US (Meat) UR (Salivation)
During Conditioning
produces
produces
+
Trial 4
Classical Conditioning
CS (Bell) CR (Salivation)
After Conditioning
produces
produces
Classical Conditioning
CS - Conditioned Stimulus (Bell)– what used to be called the neutral stimulus.
• Initially it evoked no response, but, after conditioning, it now evokes a response
CR - Conditioned Response (Salivation)– similar (but often not identical to) the
unconditioned response• but is evoked by the conditioned stimulus
Habituation and Sensitization
Can animals learn without association? Habituation
– Decreased responsiveness to repeated stimulation
Sensitization– Increased responsiveness following a
single stimulus presentation
Extinction
A reduction in the conditioned response when the conditioned stimulus is presented without the unconditioned stimulus– e.g. presenting the bell repeatedly without
the meat will eventually eliminate the salivation
Spontaneous Recovery
The reappearance of the conditioned responses following a delay in the extinction process
CR
: D
rops
of
Sal
iva
Trials
AcquisitionBell+Meat
ExtinctionBell Only
SpontaneousRecoveryBell Only
24 H
our
Del
ay
Higher Order Conditioning
First Order Conditioning:– Associating Bell + Meat Powder eventually
leads to salivation to Bell alone (Bell = CS1)
Higher Order Conditioning– Associate CS1 with a new CS (e.g. Light)
– Associating Bell + Light eventually leads to salivation to Light alone (Light = CS2)
Higher Order Conditioning
CS1 (Bell)+
NS (Light) CR (Salivation)
During Conditioning
produces
produces
+
Higher Order Conditioning
CS2 (Light) CR (Salivation)
After Conditioning
produces
produces
Important:The Light is never directly
associated with meat
Basic Rules of Conditioning
The more association trials, the better the conditioning
CS and US must be closely linked in time
Physically intense stimuli are conditioned more easily
Some things are more easily conditioned than others
Stimulus Generalizationand Discrimination Stimulus Generalization
– Animals will show a Conditioned Response to stimuli similar to the original CS
Stimulus Generalizationand Discrimination Discrimination
– If you repeatedly associate one CS with the US and do not associate the second, the CR will discriminate the two
CS+ CS-
Figure 6.4
Real-Life Examplesof Classical Conditioning Conditioning Emotional Responses
– Baby Albert (Watson and Rayner, 1920)• Conditioned fear to a white rat by
associating a loud noise with the rat– CS = rat– US = loud noise– UR = startle to loud noise– CR = startle to rat
Real-Life Examplesof Classical Conditioning Learning the meaning of words
– Word is associated with the sensory impression
• e.g. “apple” and view of an apple
– “Second-signal system”
Real-Life Examplesof Classical Conditioning Conditioned Taste Aversion
– a taste (CS) associated with a toxin (US) leads to nausea (UR)
– later, the taste alone evokes nausea (CR)
Real-Life Examplesof Classical Conditioning Drug Tolerance
– drug users become increasingly less responsive to the effects of the drug
– tolerance is specific to specific environments (e.g. bedroom)
– familiar environment becomes associated with a compensatory response
• taking drug in unfamiliar environment leads to lack of tolerance
Instrumental Learning
Pavlov– Classical conditioning of reflexes
Can learning occur with nonreflexive behavior?– Instrumental Response: a voluntary
response that acts on the environment in a meaningful way
Instrumental Learning
The modification of instrumental responses using reinforcers and punishers
E.L. Thorndike’s Puzzle Box
Cat placed in a box that can be opened from inside by pushing on latch
Initially, cat shows random behaviors– scratching– sniffing
Eventually cat will hit latch– hitting latch leads to pleasant
consequence - escape• increases likelihood action will occur again
Thorndike’s Law of Effect
Responses followed by “satisfiers” tend to be repeated
Those followed by “annoyers” are not repeated– useful behaviors are stamped in
Operants
B.F. Skinner:– An operant is an instrumental response
that operates on the environment Positive Reinforcer
– Any stimulus that increases the likelihood of an operant response
Skinner developed a general model of learning called “operant conditioning”
The Operant Chamber
Shaping Behavior
Reinforce responses that approximate the target behavior
Secondary Reinforcement
Neutral stimuli can acquire reinforcing properties through the process of higher-order conditioning– e.g. the reinforcing effect of language
(“good boy”)
Schedules of Reinforcement
Rate at which reinforcer is delivered influences nature of response
Continuous reinforcer– each response is reinforced
Partial Reinforcement– reinforcer is not delivered for each
response
Partial Reinforcement
Fixed Ratio (FR) Schedule– reinforcer is delivered only after a fixed
number of responses have been made• e.g. FR-10 schedule: reinforcer
delivered after every 10th lever press
Partial Reinforcement
Variable Ratio (VR) Schedule– the number of responses before a
reinforcer is delivered varies
Partial Reinforcement
Fixed Interval (FI) Schedule– the first response following a specified time
interval is reinforced• e.g. FI-10 schedule: only responses
made after 10 seconds are reinforced
Partial Reinforcement
Variable Interval (VI) Schedule– the first response following a varying time
interval is reinforced
Partial Reinforcement affects Response Rate
Partial Reinforcement Effect
If you train an animal using partial reinforcement, it is more resistant to extinction than one that received continuous reinforcement
Extinction– a reduction in the rate of response when a
reinforcer is withheld
Differential Reinforcement
Differential Reinforcement of a High Rate of Response (DRH)
– reinforce bursts of responses
Differential Reinforcement of a Low Rate of Response (DRL)
– reinforce pauses between responses
Behavioral Control
Skinner:
– The likelihood of any behavior depends on reinforcement and punishment contingencies
Environmental Determinism
– environmental stimuli exert total control over behavior
Stimulus Control
The Discriminative Stimulus (Sd)– a signal that indicates when a response will
be reinforced• e.g. reinforcing lever pressing only when light is
on
Negative Discriminative Stimulus (S)– A signal that indicates that a response will
not be followed by reinforcement
Stimulus Control
Responding only in the presence of Sd
and not in the presence of S
Punishment
Another potential consequence of behavior– An aversive stimulus that decrease the rate
of responding When is punishment most effective?
– It must be relatively intense– It must follow the response relative quickly– It must be applied consistently
Negative Reinforcement
Any stimulus whose withdrawal increases the probability of a behavior– e.g. pushing a lever to turn off a shock
Avoidance Learning– when an instrumental response prevents
and aversive stimulus• e.g. pushing a lever before the onset of shock
Persistence of Avoidance Learning Negatively reinforced responses show
slower extinction than positively reinforced responses– avoidance learning - gaining both positive
reinforcement and avoiding punishment
Observational Learning
Not all learning occurs through direct reinforcement
We can learn by watching others and through imitation
Limitations to Pavlov’s andSkinner’s Theories of Learning Instinctive Drift
– Animals will often show instinctive behaviors even if they are not being reinforced
• e.g. raccoons “washing” coins
Limitations to Pavlov’s andSkinner’s Theories of Learning Cognitive Maps
– Animals can create a mental representation of a maze even if they haven’t been reinforced to solve the maze
Limitations to Pavlov’s andSkinner’s Theories of Learning
Latent learning– when animals that
have not been reinforced are reinforced, they show faster than expected learning
Limitations to Pavlov’s andSkinner’s Theories of Learning Preparedness
– some associations are learned more easily than others
• e.g. associating taste with nausea is easier than associating noise with nausea
Conceptual Learning
Do associations or reinforcement explain all types of learning?
Learning to learn: – some animals can learn strategies– win-stay, lose-shift: continue response if
reinforced, switch response if not reinforece
Behavioral Complexity and Environmental Complexity The more complex the behavior, the
more complex the environment required