Students: some additional slides have been added to these lecture notes which contain material that

1
Students some additional slides have been added
to these lecture notes which contain material
that will be discussed in the first part of the
lecture prior to the exam on Nov. 29. These
slides are being made available now to aid you in
studying material from chapter 7. You will note
that we have not covered the entire chapter.
2
Sensation and Perception
Perception of Motion
Changes in the retinal size of an image indicate
if the object is moving towards or away from you
(getting bigger getting closer)
Changes in the retinal position of an image also
indicate if the object is moving
3
Sensation and Perception
Perception of Motion
There is more to motion perception than image
changes on the retina, however
Look at a page of text and nod your head up and
down (image remains stable)
Look at a page of text and move your eyeball with
a finger (image does not remain stable)
4
Sensation and Perception
Perception of Motion
Your eyes are always moving, even when
concentrating on an object
Saccadic eye movements are compensated for in the
visual system (appearance of an unmoving object)
5
Sensation and Perception
Perceptual Constancy
Why do we identify an object as being the same
object when seen from different angles, different
distances, different lighting conditions, etc?
Shape constancy we assume that an object
actually has the same shape when seen from
various angles (even though the retinal image can
change dramatically)
6
Sensation and Perception
Perceptual Constancy
Why do we identify an object as being the same
object when seen from different angles, different
distances, different lighting conditions, etc?
Size constancy we assume that objects are
actually the same size as we move towards / away
from them
7
Sensation and Perception
Size-Distance Relationship
If 2 objects cast the same size image on the
retina, depth cues (e.g., linear perspective) may
suggest that one is farther away than the other
(and therefore must be bigger)
8
Sensation and Perception
Size-Distance Relationship
9
Sensation and Perception
Lightness Constancy
We see black objects as being black and white
objects as being white even under very different
lighting conditions
The actual luminosity of an object (I.e., the
amount of light it is reflecting into your eyes)
is less important than the context (e.g., bright
sunlight vs dark classroom)
10
Sensation and Perception
Lightness Constancy
11
Sensation and Perception
Perceptual Set
What we see / hear etc is often influenced by
what we expect to see / hear
Satanic messages found when rock music played
backward
Sexual references in Disney movies
12
(No Transcript)
13
Sensation and Perception
Perceptual Set
half the class should close their eyes
14
Sensation and Perception
Perceptual Set
15
Sensation and Perception
Perceptual Set
16
Sensation and Perception
Perceptual Set
- seeing either of these...
...will influence your subsequent interpretation
of this
17
Sensation and Perception
Perceptual Set
18
Sensation and Perception
Perceptual Set
Things that are particularly important or
relevant to you (I.e., things for which you have
a well-developed schema) will be emphasized in
your perceptions
What is emphasized in a childs drawing of a
person?
19
Sensation and Perception
Perceptual Set
Most people have a well-developed schema for
faces (you have some expectations that a face
will have a particular set of features, and that
all faces share these common features)
20
Sensation and Perception
Perceptual Set
Who are these people?
21
Sensation and Perception
Perceptual Set
Your schema for faces doesnt work so well when
the faces are inverted
22
Sensation and Perception
Perception without Sensation
Extrasensory Perception (ESP)
Can humans read/receive thoughts?
Can humans predict the future?
Can humans cause physical effects at a distance
(telekinesis)?
Can humans sense events at a distance
(clairvoyance)?
23
no
(you are, of course, free to form your own
opinion, just dont call it science)
24
Learning
Learning is defined as an enduring change in the
mechanisms of behavior that occurs as the result
of experience
There are many factors other than learning which
can affect behavior
motivation
fatigue
reflexive responding
25
Learning
Traditionally, two types of learning have been
studied by psychologists
Classical or Pavlovian conditioning
Instrumental or Operant conditioning
Most current researchers probably believe that
the same basic mechanisms are involved in both
types of associative learning
26
Learning
Many species demonstrate the ability to learn
associatively
Humans
Rats
Drosophila (fruit flies)
27
Learning
Is associative learning necessary for survival?
No. In many cases hard-wired reflexive
behavior is sufficient for the success of a
species (e.g., the adult mayfly)
It does, however, come in pretty handy for us
humans (e.g., the efficient digestion of food)
28
Classical/Pavlovian Conditioning
Terminology
Unconditional Stimulus (US) a biologically
relevant event (food, sex, shock, etc)
Conditional Stimulus (CS) an event that
initially produces some orienting response, but
that has no strong biological consequences
(flashing lights, sounds, etc)
29
Classical/Pavlovian Conditioning
Terminology
Unconditional Response (UR) the unlearned
reflexive response to the US (e.g., start
sweating when room gets too hot)
Conditional Response (CR) a learned response to
a CS that predicts a US (e.g., start salivating
at the smell of food)
30
Classical/Pavlovian Conditioning
Pavlovs original experiment
31
Classical/Pavlovian Conditioning
Pavlovs original experiment
CS (tone) initially has no effect on salivation
US (meat powder on tongue) unconditionally
elicits salivation (reflexive response)
CS and US paired on repeated trials
32
Classical/Pavlovian Conditioning
Pavlovs original experiment
CS (tone) comes to elicit salivation when
presented by itself
CS has become associated with the US (it can
predict the US)
Associative learning allows for (for example)
anticipatory salivation, which makes eating a lot
easier
33
Classical/Pavlovian Conditioning
Acquisition and Extinction
Learned associations must be acquired (i.e., they
have to be learned)
the learning curve
Increased amount of total learning over time
Decreased rate of learning over time
34
Classical/Pavlovian Conditioning
Acquisition and Extinction
After sufficient conditioning, the association
will reach asymptote (maximum strength)
No further increases in associative strength,
regardless of number of additional trials
35
Classical/Pavlovian Conditioning
Acquisition and Extinction
After an association between the CS and US has
been formed by pairing them repeatedly, what
happens if we start to present the CS by itself?
Extinction of the association CS no longer
elicits CR
36
Classical/Pavlovian Conditioning
Acquisition and Extinction
What is extinction?
Not the unlearning of the association
- spontaneous recovery
- speed of reacquisition
37
Classical/Pavlovian Conditioning
Acquisition and Extinction
Spontaneous Recovery
A previously extinguished CR may reappear at the
beginning of a subsequent conditioning session
38
Classical/Pavlovian Conditioning
Acquisition and Extinction
Speed of Reacquisition
CR Strength
CR reaches asymptote faster on reacquisition than
during initial acquisition
Trial
39
Classical/Pavlovian Conditioning
Acquisition and Extinction
If extinction is not the unlearning of an
association, what is it?
The best answer would seem to be that extinction
training results in the suppression of a learned
association
40
Classical/Pavlovian Conditioning
Little Albert
- early behaviorist study by Watson Raynor
- classic demonstration of learned fear
- also demonstrates the principle of stimulus
generalization
- this study would never pass ethical review today
41
Classical/Pavlovian Conditioning
Discrimination and Generalization
Discrimination can a rat learn that a yellow
light means a shock will be delivered, but an
orange light does not? (i.e., is the distinction
between yellow and orange perceived by rats?)
Drug discrimination studies often used to assess
drug effects
42
Classical/Pavlovian Conditioning
Discrimination and Generalization
Generalization If a CR is acquired to a
particular CS, will similar CSs also elicit a CR?
43
Classical/Pavlovian Conditioning
Discrimination and Generalization
After conditioning, the CS alone elicits a CR
44
Classical/Pavlovian Conditioning
Discrimination and Generalization
What about CSs of other colours?
45
Classical/Pavlovian Conditioning
Discrimination and Generalization
Maximal CR seen in response to CS
Reduced CR seen in response to other stimuli (the
more similar to the CS, the bigger the CR)
46
Classical/Pavlovian Conditioning
Biological Predispositions
Many early theorists assumed that all stimuli
were equally associable
There is evidence, however, that some CS-US
associations are formed more easily than others
E.g., taste aversion learning
47
Classical/Pavlovian Conditioning
Taste aversion learning
Many organisms, including humans, are predisposed
to associate tastes with gastrointestinal illness
48
Classical/Pavlovian Conditioning
Taste aversion learning
There is an obvious adaptive advantage to the
predisposition to associate tastes with
gastrointestinal illness, as these illnesses are
far more likely to be the result of something we
ate than something we saw, heard, etc
49
Operant/Instrumental Conditioning
Where classical conditioning involves the
association of 2 stimuli (CS and US), operant
conditioning involves the association of a
response with an outcome
e.g., driving fast ? speeding ticket
Note that the subject is not passive here, as is
the case in classical conditioning
50
Operant/Instrumental Conditioning
Thorndikes Law of Effect
If an action has pleasant consequences, the
probability that the action will be repeated
increases if an action has unpleasant
consequences, the probability that the action
will be repeated decreases
Based on observations of cats in puzzle box
Incremental modification of behavior
51
Operant/Instrumental Conditioning
Skinner and the Operant Chamber
52
Operant/Instrumental Conditioning
Skinner and the Operant Chamber
53
Operant/Instrumental Conditioning
Skinner and the Operant Chamber
54
Operant/Instrumental Conditioning
Skinner and the Operant Chamber
55
Operant/Instrumental Conditioning
Shaping
Many responses you might wish to reinforce are
not already in the repertoire of the subject
(e.g., lever pressing in rats)
The subjects behavior can be shaped through the
use of successive approximations of the desired
behavior
56
Operant/Instrumental Conditioning
Types of Reinforcement
Type of Stimulus
Appetitive
Aversive
Present it
Positive Reinforcement
Positive Punishment
What you do
Remove it
Negative Punishment
Negative Reinforcement