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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 :

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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


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

  • 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



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





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


(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


(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 1Group 2

soft background noise loud background noise

(60-dB) (80-dB; not as intense as the tone)



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



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 fatiguesensory adaptation

muscles become incapacitated sense organs become

by fatigue 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


-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


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 long-term 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


-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 Every 3 seconds on 1 day

Tones Once a Day

Tones Once a Day


Blocks of 30 Tones


Leaton, 1976; see page 46 of Domjan


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