Mazur Chapter 9: Stimulus Control & Concept Learning Flashcards
Probe Trials
Stimuli are presented to measure the responding but no reinforcer is given
Method of measuring generalization gradients
What causes generalization gradients?
Pavlov
Innate
Generalization is an automatic byproduct of the conditioning process
Conditioning somehow spreads across to nearby neurons in the cerebral cortex
What causes generalization gradients?
Lashely and Wade
Learned through experience
Explicit discrimination training along the dimension in question is necessary before the typical peaked generalization gradient is obtained
e.g. person needs to be reinforced when a certain color is delivered but not when it is absent
Without discrimination the individual would respond just as strongly to all colors
nondifferential training
Every trial is the same
Produces a flat generalization gradient
e.g. same response rate for all frequencies
presence-absence training
Produces typical generalization gradients
Intradimensional training
same stimulus (e.g. tone) just different dimension ( e.g. tone frequency)
Produces narrower generalization gradients
e.g.frequency is only reliable cue.
Sensory deprivation and generalization
Sensory deprivation can sometimes produce peaked generalization gradients even when animals have no
prior experience with a particular stimulus dimension
In other words, experience may not always be necessary to obtain
Simultaneous discrimination procedure
Present two stimuli together (a dark gray card & a medium gray card) and the animal/human must choose between them
Differences in opinion if learning is absolute or relational [refer to other flashcards]
absolute theory of stimulus control
animal has learned about the 2 stimuli separately
e.g. the medium gray gives me food, but the dark gray does not
Relational theory of stimulus control
animal learned about the relationship b/w the 2 stimuli
it knows that the lighter gray card is associated with food
Transposition
transfer of the relational rule
e.g. if medium gray (which before predicted reinforcer) and lighter gray are presented→ they chose the lighter gray
they realized that the lighter gray always gets the food
Peak Shift
Shift in the generalization gradient in a direction away from the S-
Spence’s Theory of Excitatory & Inhibitory Gradients
Accounts for both transposition & peak shift
In intradimensional training
excitatory generalization gradient develops around the S+ inhibitory generalization gradient develops around the S-
Spence’s theory does not do a good job predicting the results on a test called intermediate size problem
Some situations respond to the absolute properties of stimuli, however, considerable evidence points to and favors the relational approach to stimulus control
Spence: associative strength
The ability of each stimulus to elicit a response
Spence: net associative strength
Determined by subtracting a stimulus’ inhibitory strength from its excitatory strength
Behavioral Contrast
Phenomenon in which responding to one stimulus changes as a result of a change in reinforcement conditions for another stimulus
Gutman and Behavioral Contrast
Gutman’s study used a type of successive discrimination procedure known as multiple schedule: 2 or more reinforcement schedules that are presented at one time, in an alternating pattern, and each schedule is associated with a different discrimination stimulus (light & noise)
1st trial- light & noise were presented alternating on the same VI schedule, and eventually response rates were the same
2nd trial-extinction trial for the noise and eventually response rates reduced for the noise stimulus
surprisingly although the reinforcement schedule did not change for the light, the response rates increased
This is called behavioral contrast
Gutman found a Positive contrast- b/c it involved an increase in responding during the unchanged light component
If the light stimulus had decreased in responding during the unchanged light component it would be called-negative contrast.
Behavioral reallocation hypothesis
Rapid responding in the unchanged component is possible because of the slower responding that occurs in the component that is changed to extinction
This gives the subject time to recover from fatigue, and they can respond faster to the unchanged component
reinforcer habituation/satiation hypothesis
The more frequently a reinforcer is presented over a short priod of time, the less effective it becomes, because of habituation, satiation, or both
Errorless Discrimination Learning
The learner typically makes few or no responses to the S-
Rather than waiting for steady responding to the S+, the experimenter introduces the S- in early in the training
Fading: An effective way to decrease the number of responses to the S – and improving the learners long-term discrimination performance
Terrace example of Fading
Terrace knew that pigeons do not usually pack at a dark key, so at first, the S- was not illuminated green key but a dark key
Using a feeding procedure, he gradually progress from a dark to a dimly lit green key, and over trials intensive the green light was increased
In other words, the S- was introduced early in training, presented very briefly at first, and it was initially a stimulus that was unlikely to elicit responding
Errorless Learning: education application
Pavlov explains that if we do not want our children to avoid school, then we need to make sure that they do not make incorrect responses b/c it could be aversive
Used fading to teach children with down syndrome shapes
First the cards only had a correct shape and two blank spaces
then very small incorrect shapes were added and over trials the sizes were increased.
Drawbacks of errorless learning
children may have difficulty learning discrimination reversal in which the S+ and S- are reversed.
may also have trouble generalizing
Learning Set
If an animals is given many discrimination tasks, one after another, each of which have a different pair of stimuli as the S+ and S-, they get faster and faster at solving the problem
Different species vary on their ability to develop new learning sets
Animals higher on the phylogenetic scales develop stronger learning sets.
Higher species have the ability to acquire more abstract info and can recognize similarities btw problems at developing a behavior strategy that improves performance on subsequent problems.
A learning set can also develop in discrimination reversal procedures- subject first acquires one discrimination and then the S+ and S- are switched. they learn quickly to switch to other stimulus
difficulty doing this may be indicator of brain damage (schizophrenics have trouble).
Exemplar Theory of Concept Learning
Category such as bird consists of the memory of many individual examples of birds the person has seen
If a novel instance occurs that is similar to the examples it will be judged to be a member
Prototype Theory of Concept Learning
A person develops a prototype–an idea of what an ideal or typical bird is like
If a new instance is similar to the prototype it becomes a central instance
If it is only moderately similar to the prototype then it becomes a peripheral instance
If it is not it will not be considered a member
Feature Theory of Concept Learning
Person judges whether a given instance is a member of the category by checking for specific features
e.g. wings, feathers, beak, 2 legs, it sings, flies…etc
The Structure of natural categories
People tend to judge category members as either typical (central instances) or atypical (peripheral instances)
Animal Studies on Natural Concept Learning
Hernstein (1979) conducted a study using pigeons and their ability to discrminate between trees and nontrees
Pigeons are able to also do concept formation with: people, water, fish, artificial objects., and even ABC letters
Other animals such as monkeys, dog are also able to do this
Pigeons can also recognize that the view they are seeing (2 dimensional) is a 3 dimensional object
Able to categorize Monet’s paintings which depicted 3D objects
Some similarities between animal & human concept learning
Animals differentiate b/w central & peripheral instances of a category ( they respond slower for an item that contains less positive features to the category)
Animals do not categorize complex stimuli simply on the basis of which individual features are present, but on how features are arranged into a whole
Concept learning is flexible→ animals can classify stimuli according to a variety of different criteria depending on the what the task demands
There is still speculation on whether animals are able to learn concepts that involved abstract relationships
Developing stimulus Equivalence
situation in which subjects learn to respond to all stimuli in a category as if they are interchangeable even though they have been taught only a few relations between stimuli, not all possible relations
Researchers believe that Development equivalence sets is closely related to the ability to learn language
This would also mean that animals should not be able to learn equivalence sets b/c they do not hold language
Vaughhan (1988) demonstrated that pigeons do have an ability to learn equivalence sets
Stimulus Control in Behavior Modification
Stimulus equivalence training
e.g. teaching children how to read
telling them to write a word down, and matching it to a spoken word
learning equivalences between ⇒ hearing a spoken word, seeing the written word, and reading the word out loud
Can also be used to teach college students a difficult topic
Stimulus Control and Study Habitss
Fox (1962) explained that poor studying is due to ineffective stimulus control
The procedure involved the students establishing a particular time, place as a strong stimulus for studying a particular subject by repeatedly pairing this time/place with nothing but study behavior.
if they were getting distracted they were asked to read one more page and go home
the students grades eventually approved, however it is unknown if the improvement is due to specifically to this type of procedure as they also received training in other areas ( recite, review.. etc)
Stimulus Control And Health Habits
Stimulus control techniques has also been done to improve eating habits/fighting obesity
Also is helpful in increasing physical activity
e.g. limiting the amount of hours of tv one watches → method called narrowing
Stimulus Control and Insomnia
Although some cases may be due to medical concerns, some are due to inappropriate stimulus control
Individuals would be instructed to :
get out of bed if you are not falling asleep within a few minutes
do not do anything other than sleep in your bed ( no reading, TV)
These instructions are used to make the proper associations so that you may fall asleep in your bed.
These procedures for training stimulus control may hinge on the reduction of incompatible behaviors to eliminate an undesirable behavior
Summary
Pavlov proposed generalization is an automatic by product of the conditioning process
Lashley & Wade said that experience is necessary for typical gradients to occur
stimulus control : absolute or relational?
spence’s theory accounts for peak shifts in generalization gradients (excitatory gradients around S+, inhibitory gradients around S-)
but does not explain intermediate size problem
Terrace developed an errorless discrimination training procedure which has been used in behavior modification programs with children
Concept formation-occurs when we treat one class of stimuli as either positive or negative
Pigeons can learn categories
Humans can learn equivalence sets, but some psychologists have found that some animals can too
Stimulus control techniques are used in behavior modification when a desired response seldom occurs in the presence of the appropriate stimulus
e.g. insomnia, studying
