This document discusses operant conditioning and B.F. Skinner's experiments with it. Operant conditioning is a method of learning through reinforcement and punishment for behaviors. Skinner designed experiments using a Skinner Box to teach rats behaviors like lever pressing through positive reinforcement with food and negative reinforcement by removing electric shocks. He found that behaviors increased most when rewards were given on a variable schedule, not consistently. The technique of shaping breaks behaviors into small steps and reinforces progress, allowing animals to learn complex actions. Skinner used shaping to teach pigeons many tasks. His work showed how reinforcement can guide learning.
2. Operant Conditioning
A method of learning that occurs through reinforcements
and punishments for behavior. We learn to perform
certain behaviors more often because they result in
rewards, and learn to avoid other behaviors because they
result in punishment or adverse consequences.
3. Operant Conditioning
Experiences shape our
future behavior choices,
even if we don’t realize
it is happening.
“Punishment” is something
bad happening to you.
“Reinforcement” is something
good happening. Remember,
“Negative” means something is
taken away, and “Positive” means
something is added to the
environment.
5. B. F. Skinner
Lived 1904-1990. Influential
American psychologist considered
to be one of the founders of
behaviorism (along with Watson
and Pavlov). He identified the
principles behind operant
conditioning, and was the first to
study the behavioral effects of
punishment and reinforcement in
highly controlled experiments.
6. The Skinner Box
Skinner’s operant conditioning chamber (also called a
Skinner Box) was designed to teach rats how to push a
lever. This behavior is not natural to rats, so operant
conditioning with positive and negative reinforcement
were performed in order to teach the behavior.
Positive Reinforcement:
A rat was awarded with food
when he pressed the lever.
Negative Reinforcement:
A rat was able to turn off
electric shocks produced by the
floor by pressing the lever.
7. Positive Reinforcement
• Initially, the rat’s behavior
was random. It accidentally
tripped the lever and a
food pellet was released.
• The rat soon discovered
that intentionally pressing
the lever resulted in a
reward.
• The consequence of
performing the behavior
(lever press) was desirable,
ensuring that the rat
would repeat the action.
8. Negative Reinforcement
• An unpleasant electric
current ran through the
floor of the rat’s cage.
• Initially, accidental lever
pushing turned off the
electric current.
• The consequence of
avoiding something painful
(removal of an unpleasant
stimulus) ensured that the
rat continued to push
the lever.
9.
10. Variable Schedule of Reinforcement
Skinner learned that behaviors become the most
frequent when rewards are not given on a consistent
schedule. Rather, rewards that are given at variable
times cause behaviors to increase greatly.
Wow! Slot
machines are so
addictive!
11. Schedules of Reinforcement
Continuous Schedule
of Reinforcement
Every time a behavior
is performed, a reward
is given.
(When first teaching a behaviour, this
schedule helps the subject learn quickly.)
Variable Reinforcement
Schedule
Behavior is reinforced/
rewarded at random
(unpredictable) times.
(In the long-run, this schedule causes the
subject to perform the behavior more
often, and remember it for longer.)
12. Shaping
To achieve a desired behavior, step-by-step trials are
used to direct the participant towards the end goal.
Skinner noticed that the pigeons in the
skinner box were not accidentally
pushing the button that would release
food. How could he teach the pigeon
that pressing the button would result in
a positive outcome?
In other words: breaking down behavior into small steps,
and giving positive reinforcement along the way can
result in the learning of more complex behaviors.
13. Shaping
Step 1: give the pigeon
food when it turns
toward the button.
Step 3: give the pigeon
food when raises its
head to the height of
the button.
Step 2: give the pigeon
food when it walks
toward the button.
Step 4: give the pigeon
food when it taps the
button with its beak.
14. Shaping: What else can we train the bird to do?
“We first give the bird food when it
turns slightly in the direction of the spot
from any part of the cage.This increases
the frequency of such behavior. We then
withhold reinforcement until a slight
movement is made toward the spot.This
again alters the general distribution of
behavior.We continue by reinforcing
positions successively closer to the spot,
then by reinforcing only when the head
is moved slightly forward, and finally only
when the beak actually makes contact
with the spot. ...In this way we can build
complicated operants which would never
appear in the repertoire of the organism
otherwise.”
16. Shaping
Skinner was able to teach pigeons many complex behaviors
- such as telling the difference between different words and
knocking bowling pins over with a miniature bowling ball.
The technique did not work
equally on all animals.
Raccoons, for example,
thought the ball itself was
food, and did not cooperate
in the experiment!
17. Shaping Humans
EXAMPLES
Learning to write. You might begin by
tracing letters. Next, by connecting dots
or dashes. Next, by looking at letters
and copying them below. Finally, by
writing the letters from memory.
Learning to eat with a spoon. First you need
to pick up the spoon. Next you need to put
the spoon in the bowl. Next you need to
scoop the food into the spoon. Next you
need to lift the spoonful out of the bowl.
Finally, you need to put the spoon into your
mouth. Encouragement from parents along
the way can reinforce these movements.
