Behavior Analysis
Lectur8
Discrimination training
Review
 Last time we talked about punishment
 The procedure of providing consequences for a behavior that
make it less likely to occur
 Two other procedures for decreasing the frequency
of behavior are


Extinction
Differential reinforcement
 If we want to increase the frequency of behavior then
reinforcement is the way to go

If the behavior does not occur by itself then we can use
prompting, shaping and chaining
Review
 All the procedures we have discussed so far are
concerned with increasing or decreasing the
frequency of behavior

Which is appropriate since solving behavior problems usually
requires changing the frequency of behavior
 But sometimes the problem isn't as simple as that
 Sometimes the problem isn't that the behavior is occurring too
much or too little
 Sometimes the problem is that the rate of behavior is
too high in one situation and too low in another
situation
Review
 In these cases we must increase the rate of behavior
in the situation in which the rate is too low
 And decrease the frequency of behavior in those
situations where the rate is too high


For example, when we learn to drive we learn to use two
pedals, the accelerator and the break.
But driving does not involve just pressing both pedals more
often


Slamming the accelerator to the floor when in traffic could be
fatal!
Learning to drive a car means learning to perform certain acts
under certain circumstances, and learning to avoid doing those
acts in other circumstances
Stimulus discrimination
 The tendency for behavior to occur in one situation, but not in another,
is called stimulus discrimination
Stimulus discrimination: the tendency for behavior to have different
frequencies in different situations
 Discriminating between two situations requires that the situations
differ in some detectable way
 E.g. students dress more formally for a job interview than they do for
my class
 This is because they can discriminate between the two situations.
 They can do this because there are detectable differences between the
two situations
 Meeting in a classroom versus an office
 Being surrounded by class mate versus being one on one with an
interviewer
Discriminative stimuli
 There are probably many more differences between
the two situations which allow us to discriminate
between them
 These differences are called Discriminative stimuli
Discriminative stimulus: any event in the presence of
which a target behavior is likely to have consequences
that affect its frequency
 For example, waiting outside an interview room,
instead of being sat in a classroom would be a
discriminative stimulus
Discriminative stimuli
 Since the consequences associated with a discriminative
stimulus can be those that either strengthen or weaken a
behavior, it follows that there are two types of discriminate
stimulus
SD : an event in the presence of which the target behavior is
reinforced
 (pronounced ess-dee)
SΔ : an event in the presence of which the target behavior is
not reinforced
 (pronounced ess-delta, the little triangle is the greek letter
delta, which actually means the letter D)
Discriminative stimuli
 So both kinds of discriminative stimuli have been
designated the letter D, for discriminative.
 Why have 2 different letters been used?
 So that we can discriminate between them! If we used the
same symbol for both kinds, we wouldn’t know what sort
of consequences the behavior would have
 So the letters D and Δ are discriminative stimuli
 Its is sometimes said that discriminative stimuli signal the
availability of reinforcement
 An SD indicates a high probability of a target behavior
being reinforced, whilst an SΔ indicates a low probability
of of reinforcement of behavior
Example
 Imagine the target behavior of Billy is crying in order
to get food.
 Now Billy's past history of reinforcement has led him
to learn that whenever he cries whilst in the presence
of his parents, his parents will give him food

In this situation, his parents serve as an SD
 Now imagine that one day Billy is at his Aunt’s
house. In the past his Aunt does not feed him every
time he cries. The target behavior has not been
reinforced.

In this situation his Aunt serves as an SΔ
Example
 Remember the definitions
 SD : an event in the presence of which the target
behavior is reinforced

In our example, when Billy was in the presence of his
parents (the event) his behavior of crying was reinforced
 SΔ : an event in the presence of which the target
behavior is not reinforced

In our example, when Billy was in the presence of his Aunt
(the event) his behavior was not reinforced
Ess-dee’s and Ess-delta’s
 Discriminative stimuli are antecedent events that are
correlated with certain kinds of consequences
 SD ‘s are correlated with reinforcement
 SΔ’s are correlated with extinction or punishment
 The functional relations between these antecedents, the
behavior and the consequences make explaining behavior
easier
 All sorts of things can serve as discriminative stimuli



A parent saying ‘dada’ is an SD for the baby to say ‘dada’
The symbol 8 is an SD for saying ‘eight’
The positions of the hands on a clock can be an SD for eating, going to
class, leaving work or going to bed!
Discrimination training
 Sometimes people don’t respond appropriately to
discriminative stimuli

For example, Billy might see his Aunty and cry
 Theses are called discrimination failures
 If Billy has not had enough training in discriminating that his
Aunty serves as an SΔ then he wont know that crying does
not work
 In these situation it is likely that whether a person
discriminates appropriately has to do with the
training they have received
Discrimination training
 Discrimination training is a set of procedures for
establishing discriminations
Discrimination training: any procedure that results in a target
behavior having different frequencies in different situations
 This training usually involves reinforcing a behavior in the
presence of the SD and not reinforcing in the presence of the
SΔ
 There are three ways of doing this
 Simultaneous discrimination training
 Successive discrimination training
 Errorless discrimination training
Simultaneous discrimination training
 With this training, people are presented with a choice.



For example we might present people with an apple and a banana, and say ‘point to the
apple’
Then if they do point to the apple they get reinforced
If they make the wrong choice then they are ignored or mildly punished, such as ‘no that’s
wrong’.
 He the apple is the SD and the banana is the SΔ
 Now the procedure I just described constitutes one training trial
 Following this we would remove the apple and banana, re-place them,
and complete the trial again


It is important in these trials to vary the position of the fruit as we want to reinforce the
behavior of pointing to the apple, and not pointing left.
If we don’t vary the position then the child will not have learned to discriminate between the
apple and the banana, he would have simply learned to point to the object on the left
 Although this training could be done with more than 2 items,
simultaneous discrimination training always involves items presented
at the same time
Successive discrimination training
 In successive discrimination training the discriminative
stimuli are presented one after the other




For example, we would hold the two fruits behind a screen.
Then we would present the apple and ask ‘what's this?
After the child answers we would provide the appropriate consequence
Then we would put the apply back behind the screen and repeat the
process either with the apple or the banana
 If the child does not know the answer then you may have to
prompt the answer in the early stages
 The successive procedure is a more difficult task than the
simultaneous one, since the alternative item is not available
for comparison.
Errorless discrimination training
 In simultaneous and successive procedures, the person will
inevitably make a number of errors.


These mistakes include failing to perform the target behavior in the
presence of the SD
And performing the target behavior in the presence of the SΔ
 For example, in training people to discriminate between a
ball and a table, we would want them to say ‘table’ when
shown a picture of a table (SD).


However on some trials it is likely that some people would say ‘ball’
when shown a picture of a table (SD)
Or they would say ‘table’ when shown a picture of the ball (SΔ)
Errorless discrimination training
 Such errors are common during discrimination training
 However errors are thought to be problematic, partly because
they can arouse emotional reactions that can interfere with
learning
 Herbert Terrace developed a procedure for establishing
discriminations essentially without errors
 It is essentially a variation of simultaneous training




The SD is presented in its usual format and appropriate behavior is
reinforced
The SΔ however is presented in a very weak form, so that it evokes no
reaction at all
For example, when asking people to name the table, we would show
table, and then we would show a faded picture of a ball
Gradually the strength of the SΔ is increased
Case study
 Some people are great at picking up non verbal cues in social





interactions
 Eg. Knowing that a smile means pleasure, or frown means
displeasure
Others are quite bad
Azrin and Hayes (1984) decided to give discrimination training to those
who struggled with interpreting non verbal cues
They asked male participants to watch a 1 minute video of a man and
woman interacting, and then asked them to rate the woman's degree of
interest.
The women on the tapes also rated their interest
The idea was that if the woman rated her interest as 2, and the man
rated her interest as a 7, then the man was mis-reading signals
Case study
 After this pretesting stage, the male students began




training.
The training was similar to the video, except they
now received feedback.
This procedure was repeated until the the students
had completed 24 trials
The researchers then took a post training measure
The researchers found that men gradually got better
at discriminating non verbal cues.
Rules for Discrimination training
 Define the target behavior
 Select appropriate discriminative stimuli and their
consequences
 Present the SD and the SΔ with appropriate
consequences
 Monitor results
Define the target behavior
 By now you know the importance of defining the
target behavior
 In discrimination training, defining the target
behavior means deciding what you want the person
to do in the presence of the SD, but not in the
presence of the SΔ
Select appropriate discriminative stimuli and their
consequences
 To do discrimination training you have to identify two or more




situations that can be discriminated in some way.
The differences that allow discrimination are the SD and the SΔ
In the initial stages of training it is important that the SD and SΔ
are sharply different in some way, so that the person being
trained is almost certain to be successful
Because failing is punishing and may make someone less likely to
try again. Additionally, you can reinforce a behavior until it
occurs
As an example, when teaching kids fruit, we would start with two
very different fruit and then move on to more similar items
Present the SD and the SΔ with appropriate consequences
 In other words, when showing a child a picture of an apple (SD) and the





child says apple (target behavior) then the consequence is ‘well done,
good Billy!’
If you show a child a picture of a banana (SΔ) and they answer with the
word apple (target behavior) then the consequence is ‘no, that’s not
right’
When working with younger or mentally retarded people it is probably
best to start with simultaneous procedure.
With older people you can start with successive training.
And moving from one procedure to another is always an option
One thing you have to be careful about is the use of punishment, it may
be best to simply ignore the incorrect answers and reinforce the correct
answers
Monitor results
 As always you must monitor the results so that you
can tell how well the training procedure is going.
 Its usually helpful to tally the successes and plot
them on a graph
Stimulus control
 When a satisfactory level of discrimination has been
achieved, we say the behavior is under stimulus control
Stimulus control: the tendency for the target behavior to
occur in the presence of the SD, but not in the presence of
the SΔ
 Stimulus control basically means that a desired level of
discrimination has been achieved
 In APA stimulus control refers to the tendency for a
particular behavior to occur in situations where it is
appropriate and not in situations where it is inappropriate

E.g. if you are a good driver then you will discriminate between red lights
and green lights!
Stimulus control
 Stimulus control is a routine and important part of
our lives
 However, naturally occurring discrimination training
sometime results in inappropriate stimulus control
 In fact many behavior problems involve
inappropriate stimulus control

For example, sometimes a student is an angel in one class in a
devil in another class. But if the one teacher has reinforced
good behavior and the other teacher has not, then the teachers
become a discriminative stimulus for appropriate behavior
Flash card!






Stimulus discrimination
 the tendency for behavior to have different frequencies in different situations
Discriminative stimulus
 any event in the presence of which a target behavior is likely to have consequences
that affect its frequency
SD
 an event in the presence of which the target behavior is reinforced
SA
 an event in the presence of which the target behavior is not reinforced
Discrimination training
 any procedure that results in a target behavior having different frequencies in
different situations
Stimulus control
 the tendency for a target behavior to occur in the presence of the SD, but not in the
presence of the SA