Download Mechanisms of Learning

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Learning is a relatively permanent change in an organism’s
behavior due to experience. In associative learning, we
learn to associate two stimuli (as in classical conditioning)
or a response and its consequences (as in operant
conditioning). In observational learning, we learn by
watching others’ experiences and examples. Learned
associations also feed our habitual behaviors.
As we repeat behaviors in a given context—the sleeping
posture we associate with bed, our walking routes on
campus, our eating popcorn in a movie theater—the
behaviors become associated with the contexts.
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Conditioning is not the only form of learning. Through
observational learning, we learn from others’ experiences.
Chimpanzees, too, may learn behaviors merely by watching
others perform them. If one sees another solve a puzzle
and gain a food reward, the observer may perform the trick
more quickly.
By conditioning and by observation we humans learn and
adapt to our environments. We learn to expect and prepare
for significant events such as food or pain (classical
conditioning). We also learn to repeat acts that bring good
results and to avoid acts that bring bad results (operant
conditioning).
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In classical conditioning, a unconditional reflex (UR) is an
event that occurs naturally (such as salivation), in response
to some stimulus. A unconditional stimulus (US) is
something that naturally and automatically (without
learning) triggers the unlearned response (as food in the
mouth triggers salivation).
A conditional stimulus (CS) is a previously irrelevant
stimulus (such as a bell) that, through learning, comes to be
associated with some unlearned response (salivating). A
conditional reflex (CR) is the learned response (salivating)
to the originally irrelevant but now conditioned stimulus.
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Pavlov repeatedly presented a neutral stimulus (such as a tone)
just before an unconditioned stimulus (UCS, food) that triggered
an unconditioned response (UCR, salivation). After several
repetitions, the tone alone (now the conditioned stimulus, CS)
triggered a conditioned response (CR, salivation).
Salivation in response to the tone was conditional upon the dog’s
learning the association between the tone and the food. Today we
call this learned response the conditioned response (CR). The
previously neutral (in this context) tone stimulus that now
triggered the conditional salivation we call the conditioned
stimulus (CS). Distinguishing these two kinds of stimuli and
responses is easy: Conditioned =learned; unconditioned =
unlearned.
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Our educational, cultural, and life
experiences shape what we perceive. As a
simple example, consider airplane cockpits.
If your knowledge of the instruments
contained in an airplane cockpit is limited,
as is the case with your author Sandy, an
airplane cockpit looks like a confusing,
meaningless jumble of dials.
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It agrees when giving experimental researches, two neuron
classes take part in formation of conditioned reflexes:
command neurons which realize specific behavioral acts and
modulating neurons, which adjust a condition of command
neurons. Before the first appearance of stimulus and
supporting reflex neurons were mainly monotouch. In process
of the further development of a conditioned reflex neurons get
ability to answer different stimulus, that is become polytouch.
After the conditioned reflex is produced, again it is observed
selective reaction of neurons - they answer only stimulus, which
became conditional irritant.
The synaptic hypothesis considers that the mechanism of
formation of a conditioned reflex is caused by change of an
overall performance of synapses.
The membrane hypothesis asserts that in a basis of the
mechanism of formation of a conditioned reflex change of
excitability of postsyneptic membrane lays.
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For development of a conditioned reflex it is necessary, that any
factor of an environment, which may be perceived by one of
analyzer systems of an organism, occur repeatedly and acted on an
organism of the person or an animal. If at each occurrence this
irritant outstrips a little or takes place simultaneously with
performance of any unconditioned reflex in an organism, probability
of development of a conditioned reflex very high. But for formation of
a conditioned reflex still it is necessary, that the brain cortex be in an
active, awake condition.
For development of a conditioned reflex the important value has
optimum force of irritant, which may become conditional irritant. Small
force irritant does not cause a sufficient level of activity in neurons of
appropriate analyzer system. In this case the conditioned reflex is
formed slowly. Such conditioned reflex exists the short period of time
and then is fast inhibited.
In real conditions irritants from the environment do not occur as
isolated factor. There are a set of similar irritants and such irritants,
which operate simultaneously
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The opportunity spreading excitation in the central nervous
system is caused by presence in it of numerous branches of
shoots of nervous cells - axons and dendrites. Shoots connect
neurons and the nervous centres in a uniform network.
Strengthening of irritation neurons stimulates distribution of
excitation on nervous circuits. Due to existence of such
communications excitation long time may circulate on closed
neuronal to circuits, till opportunities of synapses to transfer
impulses will be exhausted or there will be a braking process in
any of neurons, so the circuit will be opened.
The centre of excitation, which arises in a brain cortex under
action of conditional stimulus may be spread on neuronal circuits
in all directions. But if simultaneously in an organism the
unconditioned reflex is carried out, in a zone of cortical
representations of this reflex the prepotent centre varying a
direction spreading of excitation develops. In such a case
distribution of the excitation caused by a conditional irritant, will
be directed aside dominants.
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Dominanta (from Latin dominare - to dominate) - is the centres of
excitation prevailing in the central nervous system, which change
and subordinate to themselves activity of other nervous centres at
present. The principle of a dominant is one of main principles of
activity of the central nervous system. The Russian scientist O.O.
Ukhtomsky was formulated these principles.
The prepotent centre of excitation is characterized by such
properties:
1) Increase of excitability;
2) Stability of excitation;
3) Ability to summarize excitation - to accumulation of excitation
from stranger irritants;
4) Ability to inhibit function of other nervous centres and reflex
reactions;
5) Ability long time to keep excitation after the termination (ending)
of irritation, which has caused it (inertia of a dominant).
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I. On a way of formation:
1. Classical conditioned reflexes - are formed in natural
conditions.
2. Tool conditioned reflexes - are developed artificially. More
often they represent purposeful motor reactions. As supporting
stimulus for their development the unconditioned reflex causing
in a laboratory animal feeling of pleasure (effect of "award") or
painful irritant, causing avoidance reaction usually serves.
II. Under the relation of conditional irritant to unconditional:
1. Natural conditioned reflexes - conditional irritant it is related to
an unconditioned reflex. For example, a smell and how a food
looks have the direct relation to irritation by food of tongue
receptors, which starts unconditional salivatory discharge
reaction.
2. Artificial conditioned reflexes - conditional irritant has no the
direct relation to an unconditioned reflex which serves as a
reinforcement. For example, the bell or a light signal in natural
conditions have no the relation to unconditional salivatory
discharge reflex.
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III. On biological importance:
1. Food conditioned reflexes - provide getting food and digestion.
2. Sexual conditioned reflexes - provide sexual behavior.
3. Protective conditioned reflexes - provide defensive reactions.
4. Statokinetic conditioned reflexes - provide motor behavioral reactions
and impellent skills.
5. Homeostatic conditioned reflexes - are directed on maintenance of a
constancy of the inner environment of an organism.
III. On a degree of complexity:
1. Conditioned reflexes of the first order - the conditioned reflex is
developed on the basis of a unconditioned reflex.
2. Conditioned reflexes of the second order - the conditioned reflex is
developed on the basis of other conditioned reflex of the first order.
3. Conditioned reflexes of the third order - the conditioned reflex is
developed on the basis of a conditioned reflex of the second order.
4. Conditioned reflexes of the higher order - are formed only at the high
organization of nervous system. In human formation of conditioned
reflexes of the second - twentieth order is probably.
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B. F. Skinner (1904–1990) was a college English major and an
aspiring writer who, seeking a new direction, entered graduate
school in psychology. He went on to become modern
behaviorism’s most influential and controversial figure.
Skinner’s work elaborated what psychologist Edward L. Thorndike
called the law of effect: Rewarded behavior is likely to recur.
Using Thorndike’s law of effect as a starting point, Skinner
developed a behavioral technology that revealed principles of
behavior control. These principles also enabled him to teach
pigeons such unpigeonlike behaviors as walking in a figure 8,
playing Ping-Pong, and keeping a missile on course by pecking at
a screen target.
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Skinner showed that when placed in an operant chamber,
rats or pigeons can be shaped to display successively closer
approximations of a desired behavior. Researchers have
also studied the effects of primary and secondary
reinforcers, and of immediate and delayed reinforcers.
Partial reinforcement schedules (fixed-ratio, variable-ratio,
fixed-interval, and variable-interval) produce slower
acquisition of the target behavior than does continuous
reinforcement, but they also create more resistance to
extinction.
Punishment is most effective when it is strong, immediate,
and consistent. However, it can have undesirable side
effects.
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Fixed-ratio schedules reinforce behavior after a
set number of responses. Just as coffee shops
reward us with a free drink after every 10
purchased, laboratory animals may be
reinforced on a fixed ratio of, say, one reinforcer
for every 30 responses.
Once conditioned, the animal will pause only
briefly after a reinforcer and will then return to a
high rate of responding.
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Variable-ratio schedules provide reinforcers after an
unpredictable number of responses. This is what slotmachine players and fly-casting anglers experience—
unpredictable reinforcement—and what makes gambling
and fly fishing so hard to extinguish even when both are
getting nothing for something.
Like the fixed-ratio schedule, the variable-ratio schedule
produces high rates of responding, because reinforcers
increase as the number of responses increases.
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Fixed-interval schedules reinforce the first
response after a fixed time period.
Like people checking more frequently for the
mail as the delivery time approaches, or
checking to see if the Jell-O has set, pigeons on
a fixed-interval schedule peck a key more
frequently as the anticipated time for reward
draws near, producing a choppy stop-start
pattern rather than a steady rate of response.
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Variable-interval schedules reinforce the first response
after varying time intervals. Like the “You’ve got mail” that
finally rewards persistence in rechecking for e-mail,
variable-interval schedules tend to produce slow, steady
responding. This makes sense, because there is no
knowing when the waiting will be over.
Animal behaviors differ, yet Skinner contended that the
reinforcement principles of operant conditioning are
universal. It matters little, he said, what response, what
reinforcer, or what species you use. The effect of a given
reinforcement schedule is pretty much the same: “Pigeon,
rat, monkey, which is which? It doesn’t matter. Behavior
shows astonishingly similar properties.”
Learning by Observation
• In observational learning, we
observe and imitate others.
Mirror neurons, located in the
brain’s frontal lobes,
demonstrate a neural basis for
observational learning.
• Another important type of
learning, especially among
humans, is what Albert Bandura
and others call observational
learning.
Mirror Neurons in the Brain
• PET scans of different brain areas reveal that humans, like
monkeys, have a mirror neuron system that supports empathy
and imitation.
• Mirror neurons help give rise to children’s empathy and to
their ability to infer another’s mental state, an ability known as
theory of mind. People with autism display reduced imitative
yawning and mirror neuron activity—“broken mirrors,” some
have said.
Bandura’s Experiments
• Albert Bandura is the
pioneering researcher of
observational learning. A
preschool child works on a
drawing. An adult in another
part of the room is building
with Tinkertoys.
• As the child watches, the adult
gets up and for nearly 10
minutes pounds, kicks, and
throws around the room a
large inflated Bobo doll,
yelling, “Sock him in the nose. .
. . Hit him down. . . . Kick him.”
Experienced and imagined pain in the brain
• Brain activity related to actual pain (left) is mirrored in the
brain of an observing loved one (right).
• Empathy in the brain shows up in emotional brain areas, but
not in the somatosensory cortex, which receives the physical
pain input.
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Children tend to imitate what a model does and
says, whether the behavior being modeled is
prosocial (positive, constructive, and helpful) or
antisocial. If a model’s actions and words are
inconsistent, children may imitate the hypocrisy
they observe.
The big news from Bandura’s studies is that we
look and we learn. Models—in one’s family or
neighborhood, or on TV—may have effects—
good or bad.