PSYCHOLOGY 2250
LEARNING
Definition of Learning:
In defining learning we could refer simply to overt behavior.
For ex., if I see you riding a bicycle I can assume that you’ve
learned that skill.
Definition of Learning:
In defining learning we could also refer to an internal state of
knowledge.
For ex., you all know the 10 provinces (but I can’t tell that just by
looking at you).
So, behavior, or performance, is important.
A good definition of learning should have both components:
Overt behavior and internal state of knowledge
Learning as knowledge acquisition
Animals learn about stimuli in their environment
Such stimuli serve as signals for some important outcome
for ex., a particular odor could indicate that there is food or a
predator nearby.
Animals also learn about their own behavior
A certain action will produce a particular outcome
for ex., running to escape from a predator
Usually both types of knowledge occur together. For ex., an animal
detects a certain odor that tells it a predator is nearby and this odor
evokes an escape response, namely running, to avoid being attacked
by the predator.
Learning: is an inferred change in the organisms’ mental
state which results from experience and which influences
in a relatively permanent fashion the organisms’ potential
for subsequent adaptive behavior.
Why is learning defined this way?
Key components to definition of Learning
1. Learning is inferred from performance.
If there is no behavior to observe then we can’t say for sure
whether or not learning has occurred.
2. Learning involves a change in the mental state of an organism
We can’t see the neurological structures that underlie this
mental state but, in theory, they must exist. Acquired knowledge
must somehow be coded or represented in the brain.
3. Learning stems from experience
This distinguishes learning from instinct, which refers to
behaviors present at birth (i.e., imprinting in certain species of birds)
Key components to definition of Learning
4. Learning is relatively permanent
Learning persists through time. This part of the definition
guards against mistaking a temporary change in behavior, due to
fatigue for example, for real learning.
5. Learning is a change in the potential to behave.
An animal could acquire knowledge and yet not perform in
such a way as to demonstrate that knowledge. The organism
could have the potential to behave even though the behavior is not
occurring.
Other points:
Learning is assessed as a change in behavior —
this could mean an increase or decrease in behavior
For ex., In presence of light — barpress for food
In presence of tone — barpress for shock
What other things could influence behavior or performance
(other than learning)?
Fatigue — temporary change so not learning
Motivation — maze example; learning occurs but rat not
motivated to perform
Maturation — could also affect performance but wouldn’t
call it learning (i.e., kid reaching cookie jar on top of counter)
Domjan’s definition of Learning:
Learning is an enduring change in the mechanisms of behavior
involving specific stimuli and/or responses that results from prior
experience with those or similar stimuli and responses (p. 14)
Emphasize distinction between learning and performance
fatigue
maturation
motivation
Habituation and Sensitization
Much of behavior occurs in response to stimuli, that is, it is elicited,
as opposed to spontaneously produced.
The simplest form of elicited behavior is reflexive behavior.
-knee-jerk reflex
-a loud noise causes a startle response
-puff of air at the cornea makes the eye blink
These are all reflexes.
A reflex involves 2 closely related events:
-eliciting stimulus
-corresponding response
The response and stimulus are linked
-presentation of the stimulus leads to the response and the
response rarely occurs in the absence of the stimulus
(i.e., you don’t go around kicking your leg out unless someone
taps you on the knee).
The specificity of the relation between stimulus and response is a
consequence of the organization of the nervous system.
Simple reflexes involve three neurons:
(1). Sensory— afferent— to spinal cord
(2). Motor— efferent— to muscles
(3). Interneuron — sensory and motor neurons often
don’t communicate directly.
This is known as the reflex arc (see Fig. 2.1)
Other forms of elicited behavior
Two of the simplest and most common forms of behavioral change
are:
(1). Habituation—defined as a progressive decrease
in the vigor of an elicited response that may occur with repeated
presentations of the eliciting stimulus.
(2). Sensitization— defined as an increase in the vigor
of elicited behavior that may result from repeated presentations
of the eliciting stimulus.
Habituation and Sensitization occur in a wide variety of response
systems and are therefore fundamental properties of behavior.
Because elicited behavior involves a very close relationship
between the eliciting stimulus and the resulting response,
people often think that the behavior is invariant, or fixed.
The common assumption is that elicited behavior will occur the
same way every time the stimulus is presented--not true!
Behavior is plastic — it changes— it does not occur the
same way every time.
Procedures used to study Habituation and Sensitization
(examples of repeated stimulation):
1. Visual attention in human infants
In babies, visual cues elicit a looking response which can
be measured by how long an infant keeps her eye on one object
before shifting her gaze.
A study by Bashinski, Werner & Rudy (1985)-described
on p. 37 of Domjan.
2. Startle response in rats
A study by Davis (1974)-described on p.38 of Domjan
The startle response is a defensive response in many
species
(i.e., present loud noise, you jump).
In rats, we can measure startle in a stabilimeter chamber
Rat jumps, chamber bounces and sensors detect the amount
of movement
Davis investigated startle in rats by presenting a loud tone.
2 groups of rats
-each received 100 tones at 30 sec intervals (110-dB)
-noise generator that provided background noise
Group 1
soft background noise
(60-dB)
Group 2
loud background noise
(80-dB; not as intense as the tone)
Results:
Repeated presentations of the tone did not always elicit the
same response
With soft background noise, repetitions of the tone resulted in
weaker startle response (i.e., habituation)
In contrast, when the background noise was louder, repetitions
of the tone resulted in a bigger startle response (i.e., sensitization)
With the same tone, see 2 different patterns depending on other
circumstances.
These 2 studies show that increases or decreases in responding
can occur with repeated presentations of stimuli
Decreases in responsiveness by repeated stimulation = Habituation
Increases in responsiveness by repeated stimulation = Sensitization
Lots of everyday example: grandfather clocks, trains
Habituation is a decline in the response that was initially elicited
by a stimulus
However, habituation is not the only effect that can produce
a decrease in response
Must distinguish habituation from:
response fatigue
muscles become incapacitated
by fatigue
sensory adaptation
sense organs become
temporarily insensitive
(i.e.,won’t respond to
visual cues if you’re
temporarily blinded by a
bright light)
Habituation is stimulus-specific
-if you present a different stimulus, the animal will make
the response
-shows that they are not fatigued if they can still make the
response
-rules out response fatigue
Habituation is response-specific
-an animal may stop responding to a stimulus in one aspect
of its behavior but continue to respond in other ways
-e.g., orienting response to mother’s voice may habituate but
still listen to what she is saying
-rules out sensory adaptation
Sense organ
Sensory
neuron
Central
Nervous
System
Site of sensory
adaption
Muscle
Site of response
fatigue
Motor
neuron
Site of habituation
and sensitization
Dual-Process Theory
Habituation and Sensitization effects are changes in
behavior or performance
But what factors are responsible for such changes?
The Dual-Process Theory (Groves & Thompson, 1970)
was an attempt to get at this issue
The DPT assumes that different types of underlying
neural processes are responsible for increases and decreases in
response to stimuli.
The habituation process produces decreases in responding
The sensitization process produces increases in responding
These 2 processes are not mutually exclusive— they may be
activated at the same time.
The behavioral outcome depends on which process is stronger.
Net effect = summation of habituation and sensitization processes
(not to be confused with habituation and sensitization effects)
process = underlying neural process/mechanism
effect = behavior (what you actually observe)
if you observe habituation, might still have sensitization process
activated, but its not very strong
Groves & Thompson suggested that habituation and sensitization
processes occur in different parts of the nervous system.
Habituation processes are assumed to occur in the S-R system
-the shortest neural path connecting the stimulus
and the response (sense organs and muscles)
-similar to the reflex arc
Each presentation of the stimulus activates the S-R system
and causes some build up of habituation
Sensitization processes are assumed to occur in the state system
-this system consists of other parts of the nervous system
that determine the organism’s general level of responsiveness or
readiness to respond
-only arousing events activate state system; not necessarily
activated with every stimulus presentation.
The state system determines the animal’s readiness to respond,
whereas the S-R system enables the animal to make the specific
response that is elicited by the particular stimulus
Changes in behavior that occur with repeated presentations of a
stimulus reflect the combined actions of the S-R and state systems
Back to Startle Response in rats:
When the rats were tested with the quiet background noise,
there was little to arouse them – the state system was probably
not activated
- repeated presentations of the tone activated only the
S-R system and the result was habituation of the startle response
When the rats were tested with the loud background noise, the state
system was activated and the result was an increase in the startle
response to the same tone.
The State and S-R systems are activated differently by repeated
presentations of a stimulus
The S-R system is activated every time a stimulus elicits a response
-it is the neural circuit that conducts impulses from sensory
input to response output
The state system only becomes involved in special circumstances
-e.g., when stimulus is intense
Characteristics of Habituation and Sensitization
Time course
Sensitization is usually temporary
-sensitization can last for up to a week but not generally a longterm effect.
-with a stronger stimulus, the effects last longer.
Habituation can be short-term or long-term, depending on
presentation and interval between stimuli.
Short-term habituation:
-rapid presentations of a stimulus with a short interval between
presentations
-results in habituation quickly but see spontaneous recovery
-the degree of spontaneous recovery depends on length of
rest interval.
Long-term habituation:
-one stimulus presentation a day
-see more long-term effects
-see less spontaneous recovery
Tones Once a Day
Tones
Tones Every 3
seconds on 1 day
Blocks of 30 Tones
Leaton, 1976; see page 46 of Domjan
Tones Once a
Day
Tones
Stimulus specificity
Habituation is stimulus-specific
-if you change the stimulus, see recovery of the response
Sensitization is not highly stimulus-specific
-if an animal is aroused, it is usually aroused to a variety of cues
Effects of strong extraneous stimuli
If you change the nature of the eliciting stimulus you see recovery
of the habituated response.
Can also see recovery of the response if the animal is given a rest
period = spontaneous recovery.
The response can also be restored by presenting a strong stimulus—
this is called dishabituation.
Dishabituation refers to recovery of the response to the
habituated stimulus following presentation of a different, novel
stimulus.