In the last section, we began
talking about some aspects of classical conditioning and some variables that
were associated with the classical conditioning. In this section, we’re
going to begin to determine whether or not, and what factors determine
whether a conditioned response will actually develop. We begin this process
by discussing the concept of contiguity, which is shown in slide two.
In essence, what contiguity says is this, that the
conditioned stimulus must precede the unconditioned stimulus, even if only
for a brief time period. In general, the longer the delay between the
conditioned stimulus and the unconditioned stimulus, the poorer the
conditioning. We will talk about this in more detail as we talk about this
concept in schedules of conditioning.
In essence, what’s happened is that the conditioned
stimulus as we see in slide three, must act as a cue, and the conditioned
stimulus that provides the most reliable information about the occurrence of
an unconditioned stimulus is going to be chosen over all the other stimulus
cues that are present in the environment. In essence, the conditioned
stimulus must predict the unconditioned stimulus the best. However, other
cues could also prevent or block the development of the conditioned response
and we will talk about that at a little bit later time.
Now when we’re talking about classical conditioning, as we
see in slide four, there’s an optimal period for learning. It also depends
on the organism, the conditioned stimulus that we’re using, and the
unconditioned stimulus we are using. Let’s give some examples to give us
some context.
The classic example begins with looking at an eye blink
reflex. What we want to do when we present the conditioned stimulus and the
unconditioned stimulus is to have it very rapid. And as you see with the
other ones as we go down the list, two seconds for skeletal movements, four
seconds for salivary responses and on and on and on. We can see this change
and increase in time occurs. The question becomes why? Primarily it is due
to the latency of respondents, or responding in the particular reflex
system. So, it’s not just the fact that we’re having the relationship
together, but that there’s an optimal period of time for the presentation of
the CS and the unconditioned stimulus. And as we see in slide five, there is
an actual relationship that you can do. This changes for each type of system
and learning.
Now there’s one exception to this rule and that is shown
in slide six. This is called Poison Based Avoidance Conditioning (also
called PBAC). Long, delayed conditioning can also occur (several hours) The
question becomes why? What is an example of this particular issue?
Poison based avoidance conditioning, basically occurs when
an organism eats some food, a period of time elapses (could be hours), and
the organism gets sick. The classic example goes something like this. A long
time ago in a galaxy far, far away I went to a restaurant and had a new dish
( of food) that I had never tried before. And after eating that food, I went
home. In about seven or eight hours I got astronomically sick (puking,
vomiting, etc.) From then on, I have never liked that particular food, and
I’ve never had that particular food again. Why, because I developed an
association between the particular food and the nausea and vomiting. Now in
all likelihood, I probably had some stomach flu or something else. But that
hasn’t changed my view of this particular type of food and I still haven’t
eaten it since.
A second variable that will determine whether a
conditioned response will develop is shown in slide seven. This relates to
the strength of the unconditioned stimulus. In general, the stronger the
unconditioned stimulus, the faster the learning. And the stronger the
unconditioned stimulus, the higher the level of the unconditioned response
that occurs.
In addition,as we see in slide eight, the strength of the
conditioned stimulus will have a major impact on the conditioned response.
Also, the strength of UCS can significantly influence the CR. Sometimes, a
conditioned stimulus will cause a conditioned response to increase and
sometimes it doesn’t. The question becomes why? When you only get one
conditioned stimulus, you may get a weak conditioned response, but if you
get a weak and a strong CS, you will get greater conditioned responding to
the strong conditioned stimulus. For example, if you are giving two tones,
(a weak tone versus a strong tone) the organism will go for the strong tone
over the weak tone.
The next variable that will determine whether a
conditioned response will occur is shown in slide nine and that’s the
saliency or the nature of the conditioned stimulus. Stimuli differ in their
abilities to become associated with UCS. That is, some will become
conditioned and some will not. Salience, in essence, refers to the degree of
associative ability (how things that will cause that particular pairing to
occur). In essence, salient stimuli become highly associated and non-salient
stimuli do not become associated.
The next variable is, relates to the conditioned stimulus
delivery. This is shown in slide 10. That is, the conditioned stimulus must
precede the unconditioned stimulus and no conditioning will occur if the UCS
occurs without the CS as often as occurs with it (50/50 ratio presentation).
In essence, what this means, is that there must be some predictability of
the CS with the UCS. No conditioned response will occur if the CS occurs
without the UCS. That is, if you ring the bell alone, no conditioned
response actually occurs.
The next variable is called predictiveness. This was shown
by Bowles. Bowles believed that the contiguity of stimuli was not enough.
That is, the events must occur together before we get a conditioned
response. However, as we talked about earlier, the CS must predict the UCS
and not some other stimuli. So, of all the stimuli that are out there, and
all the unconditioned stimuli that are out there, the CS must predict one
particular UCS and not some neutral stimulus or conditioning will not occur.
The next concept, as we see in slide 12, relates to
blocking. Bowles suggested the cues must first, predict the UCS and provide
information not signaled by other cues in the environment. A man named Kamin
basically demonstrated that the presence of
positively - predicted cues will prevent or block the
development of an association with a second cue. This is shown in an
experiment beginning on slide 14. In phase one, Kamin gave rats a
distinctive CS (a light), and then he paired it with the UCS (a shock). Then
he gave a second phase. He put rats in the two groups. The rats in the
experimental group received eight pairings of light with the conditioned
stimulus and a second cue (a tone). So, we present a light, then we’re
present a tone and then the shock. A control group only received the tone
with the shock but no light. The results showed when he presented the light
only, the rats didn’t bar-press. When he presented the tone only, the rats
continued to bar-press. That is, it had no effect. The light became
associated with the shock and the tone did not. That is, the light blocked
the tone and so the rats in the experimental group continued to bar press,
but the rats in the control group did not continue bar press. The question
for this is shown in this next slide, why?
In essence, what happens, says Kamin is that the presence
of the light causes the experimental animals to not pay attention to the
tone. For surprise, they receive the shock. So in essence, surprise causes
the rats to associate the light with the shock. Later on, when you present
the light with the shock, the animal was always surprised before the tone
was presented. So in essence what we find is when we present CS1, then CS2 ,
and then the unconditioned stimulus, over a period of time and pairings, CS1
will in essence block CS2.
That is different from higher order conditioning where CS2
is presented first, then CS1, and a conditioned response occurs. In essence
CS2 and in higher order conditioning causes a conditioned response. So
there’s a difference. In blocking, you have CS1, then CS2, then you get a
conditioned response. In higher order conditioning, you get a CS2 then a CS1
and then the conditioned response. I would suggest that you write these
down, the differences between these two, and make sure that you understand
them for our discussions at a later time.
And so we will close in this section and we’ll begin by
talking about some other variables shortly, so until that time, have
yourself a great day.
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