PSYC 4032 EXAM 2 STUDY GUIDE: CHAPTER 3: PAVLOVIAN LEARNING (CONDITIONING)

1.        Recall that we started this course by looking at selected behaviors that, by definition were NOT learned (reflexes, Fixed Action Patterns, etc.) Reflexes = "HARD WIRED" neurological responses to environmental stimuli. They can fluctuate somewhat in intensity (habituation and sensitization), much like the brightness from  light bulbs fluctuate with changes in voltage—but basically we come into the world with these circuits ready to go – out of the box er... uh... womb ... so to speak.

2.        Ivan Pavlov was a Russian physiologist who studied the mechanism of a set of reflexes, specifically digestive reflexes... the reflexive secretion of various enzymes from localized glands in the digestive tract when foods (hopefully) are ingested.

3.        His fame as a scientist (physiologist) resulted from his innovative surgical techniques. He developed ways of exteriorizing the ducts of various glands (stomach, gallbladder, pancreas, etc.) so that the experimental animal was not in any pain (this was VITAL to him and in fact, the relationship between experimenter and animal was what allowed his later learning theories to develop) and could continue to function and eat normally. This methodology (experimental preparation) allowed him to collect various digestive secretions from various glands and examine their chemical composition to determine how they enzymatically turned food into energy  (for what its worth... he basically won a Nobel prize for figuring out how your lunch turns into you).

4.        Pavlov was fascinated by the adaptability of the glands. For example, with the salivary glands, he found that hard dry food = heavy salivation but
wet food = light salivation
acidic food = heavy alkaline salivation, etc.

5.        Although he went on to win to the Nobel Prize for his surgical and physiological investigations—he began to “scare” his peers by saying “Non-Physiological” things like "the psychic intelligence of the glands"

6.        He  became particularly fascinated by the observation that the subjects (dogs) would sometimes begin salivating BEFORE they ate anything—usually when himself or a favorite lab tech would enter the lab to start the day's work.

7.        In the final analysis—the questions that kept “itching” at Pavlov were:

        “How can a gland have intelligence?” or

        “How can reflexes (which are supposed to be unlearned, hardwired behaviors) show CHANGES DUE TO EXPERIENCE?” (this is the definition of learning from chapter 2 no?)

        He risked the ridicule of his peers when he left the science of physiology to enter the realm of what was then thought of as being “the psychic friends network" (It must have been like the reaction of the folk music community when Dylan went “electric”...oh... well... whatevernever mind).

8.        Through careful observation Pavlov concluded that there were two (2 kinds of reflexes)

• The inborn-permanent ones that we talked about in chapter one called UNCONDITONED REFLEXES (UR's) and ORIENTING RESPONSES (OR's) 
• Another kind that is NOT present at birth—it is Aquired through Experience.He called these CONDITIONED REFLEXES (CR's) because they actually depend upon many CONDITIONS!

9.        IMPORTANT!!:   Pavlov's specialty in PHYSIOLOGY was digestion SO.... to him SALIVATING TO FOOD was the UR and turning one's head (ears) a bell/tuning fork was the OR

(BUT.... he could have been an auditory physiologist—and you may be tempted to think that we would then learn his theory as salivating to food = OR and...head turning to food = UR

WRONG...it turns out certain reflexes are more easily conditioned to some stimuli but not others... and none of this would have worked if it would have been referenced toward the auditory ORIENTING REFLEX (OR).

10.        So to summarize: Pavlov was a physiologist studying digestion. In the course of his work investigating the enzymatic composition of saliva he noticed what he called the "intelligence of the glands" – the amount and         composition of salivary secretions was exquisitely tuned to the amount and type of food placed in the mouth. But it went beyond this; because he was so accurate in his operational definition of the salivary response and so precise in its measurement—he was able to detect that after working with a test subject (dog) for a while... the animal would begin to secrete saliva before it had any food placed in its mouth. Almost as if the salivary gland  had "psychic powers". Given the low esteem with which other scientists held psychology, Pavlov did NOT want to publicly admit to studying inner life of the mind... but he could NOT let go of the urge to know what was going on here... he decided to go for it.

11.        Because the thing about these psychic secretions that struck him as the most interesting was the fact that the dogs would start salivating when an experimenter who had become attached to the dog would enter the testing room (open the door, footsteps etc) Pavlov decided to set up a very controlled environment in which he could isolate the important stimulus elements of that situation.

12.        He knew that both the orienting reflex (OR)(to an auditory stimulus) and the salivation reflex (to food in the mouth) were inborn and unconditional.

13.        To recreate the original conditions under which he first observed the "psychic secretions" he began testing dogs as follows:

        a)         strike the tuning fork and wait for + 1 second

        b)         place the food in the dog's mouth

        c)         record salivation rates throughout (operationally defined by the gauge etc)

        d)         at first—nothing unusual, the US-->UR  and the NS--->OR

        e)         however after repeatedly paring the NS and US something weird happened!

        f)         the NS produced a “UR like” reflex: Salivation INSTEAD of the OR

14.        Dogs are NOT born with a hardwired salivary reflex to sounds (DUH!) so once the dog began to salivate after hearing the tone... Pavlov realized that he had a behavioral phenomenon that was NOT a product of NATURAL SELECTION! (NOT a reflex, fixed action pattern, or inherited behavioral trait)

15.        Each pairing of the NS/CS and US is one trial and the procedure is known as Pavlovian or classical conditioning. Two (2) important features of Pavlovian procedure are

17.    Contingency (Predictability)
In order to examine whether contingency is important above and beyond the number of times the CS and US occur together, you could require a procedure in which the correlation between CS and US occurrence is varied while the total number of times the subjects are exposed CS-US pairings are held fixed. An experiment which examined this question was devised by Rescorla (1968). He took four groups of rats and exposed them all to tone-shock pairings While a target behavior (lever pressing was occuring-- the Dependent Variable of the CR is going to be the degree to which that lever pressing is suppressed by the CS). In each test session the animals heard a number of 2 minute tones interspersed by silences. For all groups the probability that they would experience a shock while hearing the tone was 0.4. The groups differed in the probability that they were also shocked during the silences occurring between tones - one group received no shocks during these intervals (a probability of 0.0), the other groups received shocks during the 'no tone' intervals with probabilities of 0.1, 0.2 and 0.4. So, although all the groups receive the same number of tone-shock pairings the tone becomes a progressively better predictor of shock as the probability of shock occurring during the 'no-tone' intervals decreases. He also tested a control group who received no shocks but heard the same number of tones as the experimental groups. The results below clearly show that CS-US predictability is an important factor in determining the efficacy of conditioning - the more the experimental groups were shocked during no-tone intervals the less the tone could predict shock and the less an ongoing target behavior (lever pressing) was suppressed by the tone (see the diagram below):
In trying to explain the classical conditioning process, experiments where two (or even more) CSs are presented with a single US were conducted. By varying aspects of the CSs and comparing the effectiveness of their conditioning to the single US the scientists hoped to discover what properties of the CS (and, eventually the US), as opposed to the CS-US pair, determine the effectiveness of conditioning. Probably the simplest experiment comparing two CSs is a demonstration of the phenomenon of overshadowing. In this experiment two CSs, CS1 and CS2, are always presented together during training. In the test-phase, the strength of conditioning to the stimuli CS1 and CS2 presented individually are measured. The typical outcome shows that the strength of conditioning to each CS depends on their relative intensity. If CS1 is a dim light and CS2 a bright light then, after conditioning to the CS1-CS2 combination, the CR to the bright light is very strong while the dim light alone produces little or no reaction.

19.    Blocking
In addition to variations in the subjective characteristics, variations in the history of these experiences were also investigated. Suppose that two stimuli CS1 and CS2 will be paired with a single US. Rather than presenting the two CSs together throughout the training of an animal only CS1 is used in the first half of training and later the CS1-CS2 combination together, just as in an overshadowing experiment for the second half of training. The result, in general, is that when subsequently tested individually the animal will show strong conditioning to CS1 and little or no conditioning to CS2. The effect where the prior pairing of one stimulus with a US stops the US being associated with other subsequently presented stimuli is called blocking. 
Procedure for a simple blocking experiment:

Group Name	1st Training	2nd Training	Test
Blocking	CS1-US	CS1-CS2 and US	CS2 alone
Control	nothing	CS1-CS2 and US	CS2 alone

To control for the possible confounding effects of overshadowing, experiments were conducted, in which the roles of CS1 and CS2 were reversed so that CS2 was experienced paired by itself with the US in the 1st training before the 2nd training with the CS1-CS2 compound stimulus. In this experiment normally strong conditioning to CS2 and little conditioning to CS1 would be expected. 
In order to compare the effectiveness of overshadowing vs. blocking and include some measure for the predictability of the CSs, a "blocking and predictability" experiment could be devised:

Group Name	1st Training	2nd Training	Test
Correlated	Correlated CS1 and US	CS1-CS2 and US	CS2 alone
Uncorrelated	Uncorrelated CS1 and US	CS1-CS2 and US	CS2 alone
Overshadowing	US alone	CS1-CS2 and US	CS2 alone
No US	CS1 alone	CS1-CS2 and US	CS2 alone

when this has been done the strength of conditioning to CS2 acquired during 2nd training was much weaker in the group which had received prior correlated parings of CS1 and the US than in the groups which had received no prior pairings (overshadowing) or which had received random presentations of CS1 and the US. Finally, the group which had received CS1 alone with no US in phase 1 showed even stronger conditioning to CS2 than the overshadowing or uncorrelated controls.

20.    Rescorla and Wagner's model of classical conditioning
This is an example of Preparatory Response or information processing explanation of Pavlovian Learning.
According to Rescorla and Kamin, associations are only learned when a surprising event accompanies a CS. In a normal simple conditioning experiment the US is surprising the first few times it is experienced so it is associated with salient stimuli which immediately precede it. In a blocking experiment once the association between the CS (CS1) presented in the first phase of the procedure and the US has been made the US is no longer surprising (since it is predicted by CS1). In the second phase, where both CS1 and CS2 are experienced, as the US is no longer surprising it does not induce any further learning and so no association is made between the US and CS2. This explanation was presented by Rescorla and Wagner (1972) as a formal model of conditioning which expresses the capacity a CS has to become associated with a US at any given time. This associative strength of the US to the CS is referred to by the letter V and the change in this strength which occurs on each trial of conditioning is called dV. The more a CS is associated with a US the less additional association the US can induce. This informal explanation of the role of US surprise and of CS (and US) salience in the process of conditioning can be stated as follows:
dV = ab(L - V)
where a is the salience (intensity) of the US, b is the salience (intensity) of the CS and L is the amount of processing given to a completely unpredicted US. In words: when the US is first encountered the CS has no association to it so V is zero. On the first trial the CS gains a strength of abL in its association with the US which is proportional to the saliences of the CS and the US and to the initial amount of processing given to the US. As we start trial two the associative strength is V is abL so the change in strength that occurs with the second pairing of the CS and US is ab(L - abL). It is smaller than the amount learned on the first trial and this reduction in amount that is learned reflects the fact that the CS now has some association with the US, so the US is less surprising (cute...very cute--oops I'm not supposed to impose my opinions). As more trials ensue, the equation predicts a gradually decreasing rate of learning which reaches an asymptote at L.
However, the diagram below shows: this is not what is seen when the development CS-US associations is measured over time. Instead the learning curve is sigmoidal. Rescorla has argued that the equation is consistent with observed behavior if one assumes that very small changes in associative strength are undetectable and that there is a limit to the amount of effect that very large changes can have on behavior.

CS-US aquisition
There are other respects, however, where the model performs better in predicting experimental outcomes. It can also be applied to a number of CSs each of which contributes to an overall associative strength V of the US in the right hand side of the equation. It is reasonably clear that the presence of the CS salience term b in the equation lets it account for overshadowing. The meaning of the equation is clearest if the specific dVs on the left hand side are seen as referring to the increments in association between specific CSs while V on the right hand side is referring to the predictability of the US and so is the sum of all the different CS-US associations. If the conditioning strength accrued to CS1 is denoted by dV1 and that to CS2 by dV2 then our equations are:
dV1 = ab1(L - V)
dV2 = ab2(L - V)
and both dV1 and dV2 accrue to V on each trial. The amount of association directed to each CS is proportional to their salience.
The equation also models blocking well. During the initial phase of a blocking experiment the associative strength of the US is increased so later, when a second CS is presented the amount of associative strength it can gain has been reduced.
The critical question is, however, does the model predict experimental outcomes it was not explicitly divised for, i.e. can it be generalized? In one example the model predicts the effects of pairing two previously learned CSs on learning about a third new stimulus. If on separate occasions (not as compound stimuli) two CSs of equal salience have both been completely associated with a US then V=L for both stimuli and dV on subsequent trials is zero for both. Now a third CS in conjunction with the original pair is presented so three CSs are presented together whereas only two of them were presented singly in the past. The overall associative strength of the US is now 2L, a contribution of L from both of the original CSs. The equation predicts that there will be a negative change in associative strength on this trial proportional to the salience of the CSs:
dV = ab(L - 2L)
dV = -abL
Conducting the experiment shows: the third stimulus becomes a conditioned inhibitor of the US - it provokes a CR of the opposite quality to that produced by the other two CSs.
So you can see that there is more to this stuff than a drooling dog...for best results please read Chapter 3 (and keep it out of reach of small children).