The Antecedent

1. Discriminative Stimulus (S^D)

Before you learn the steps involved in the two categories of discrimination training, there are some definitions you need to know. These terms will be used regularly by other behavior technicians and by BCBAs. Therefore, you are expected to memorize and understand each of these definitions.

Stimulus/stimuli (singular/plural) is anything that one sees, hears, smells, tastes, or feels.

EXAMPLE

All of these are examples of stimuli: 2D photo of a cookie, an actual cookie, the smell of cookies baking.

S^D stands for discriminative stimulus. What does this mean? The technical definition of discriminative stimulus (S^D) is a stimulus in the presence of which a particular response will be reinforced and in the absence of which that response will not be reinforced.

A stimulus is called a discriminative stimulus (S^D) when it signals that a correct response to the stimulus will result in reinforcement. It is an instruction or cue to the patient that evokes a response. Keep in mind that S^Ds are not just questions or instructions, but can also be nonvocal cues such as pointing or a sign indicating something such as a stop sign.

EXAMPLE

A red light cues you to stop at an intersection.

EXAMPLE

Someone waves, and you wave back.

EXAMPLE

“What is your name?” evokes your response, “Jesse.”

Something is said to have stimulus control when there is a change in the occurrences of behavior due to a particular stimulus.

EXAMPLE

In this example, the phone ringing goes from being a stimulus to a discriminative stimulus, or S^D, when you answer the phone and receive reinforcement for doing so (someone on the other line says hello) in the presence of the stimulus, which is the ringing.

EXAMPLE

In this instance of a photo of a girl eating, note that an S^D does not have to be vocal. It can be something the patient sees, or smells, or tastes, or touches. In this case, we want to establish a picture of a girl eating as the S^D that evokes the response, “Eating,” or “The girl is eating,” or “She is eating.”

EXAMPLE

In this case of a picture of a dog in a book, we want to establish a picture of a dog as an S^D that evokes the response, “Dog,” or “It’s a dog,” or “I see a dog.”

EXAMPLE

In this last scenario, where Mom asks, “What did you do at school today?”, we want to establish the question, “What did you do at school today?” as an S^D that evokes a response about what the teen did at school on a given day.

think about it

Come up with your own example of an S^D.

terms to know

Stimulus/Stimuli (singular/plural)

Anything that one sees, hears, smells, tastes, or feels

Discriminative Stimulus (S^D)

A stimulus in the presence of which a particular response will be reinforced and in the absence of which that response will not be reinforced

Stimulus Control

A change in the occurrences of behavior due to a particular stimulus

2. Types of Discriminative Stimuli

Most of the stimuli and discriminative stimuli (S^Ds) we present are either vocal S^Ds, visual S^Ds, or a combination of vocal and visual.

2a. Vocal Discriminative Stimuli

EXAMPLE

“What does a cow say?”

EXAMPLE

"Tell me something that is red.”

2b. Visual Discriminative Stimuli

EXAMPLE

A toy cow, picture of a cow, real cow, etc. We might hold up a toy cow as the S^D for the patient to expressively label the cow, that is, to say, "Cow."

EXAMPLE

A red apple, green apple, sliced apple, etc.

2c. Combination of Vocal and Visual Discriminative Stimuli

EXAMPLE

Holding up a toy cow (visual) and asking “What is this?” (vocal)

EXAMPLE

Pointing to a picture of a boy sleeping (visual) and asking “What is he doing?” (vocal)

3. Guidelines for S^Ds

There are six guidelines that should be followed for presenting S^Ds:

1. Have the patient’s attention before you present the S^D.

This is important because if you fail to gain the patient’s attention, they are unlikely to respond and you are setting them up for failure.

2. Avoid presenting the patient’s name with the S^D.

So, in the example with DeShawn, if he wasn’t looking at the behavior technician and they wanted to get his attention, they might have said, “DeShawn,” and when he looked, she would have reinforced the eye contact and then gone on to present her other S^Ds.

Keep in mind that the name may become an extraneous variable that the patient comes to “ignore” so that when you call the patient’s name to gain their attention, they will not respond.

Or, the patient may start to respond only when their name is at the start of the S^D. When we are speaking with typically developing individuals one on one, we do not need to call their names to get them to answer us. We do this with individuals with ASD because it may be harder to get their attention. However, if we call their names before the presentation of each S^D, we are compensating for their poorer attention, rather than teaching them to attend to us.

hint

It’s okay to sometimes use the patient’s name with the S^D, but when we find ourselves doing this frequently, it usually means the patient is not making eye contact with us and we are trying to compensate by calling the patient’s name. If you experience this, you should speak with your patient’s BCBA about other ways to gain the patient’s attention.

3. Avoid repeating S^Ds without giving consequences.

This is the correct way because the patient will not respond consistently. We want the patient to learn that every time we present an S^D, a response is expected.

4. Change target S^D only when BCBA instructs you to do so.

It will slow the patient’s progress if every behavior technician works on their own target in a program.

5. Initially, S^Ds should be clear and concise.

Please note that “initially” is underlined. After our patients have learned beginning level language skills, vocal S^Ds or instructions must become more complex and less concise. As such, for a patient further along in their program, “Can you please come over here and sit down?” would be an appropriate way to present an S^D.

hint

You will not have to make these decisions alone; your BCBA will tell you how complex your instructions should be for a given client.

think about it

Consider why this is important. Imagine you are learning a new language and you want to learn to ask for an apple. Which way will you learn more quickly? A) “Look at this, we call this an apple. Repeat after me.” or B) “Apple.”

6. The patient should respond only after the entire S^D is presented.

This is important because if the patient responds before the S^D is completed, they are not responding to the S^D. Therefore, the patient is not learning what it is we are intending to teach.

4. Motivating Operations (MOs) and Establishing Operations (EOs)

The other aspect of the antecedent we will cover in this training is the motivating operation, or MO. In some cases, the antecedent in a discrete trial may include a condition or physical state that motivates the patient to respond to an S^D or even to respond when no S^D is present. An MO can also make a person less motivated to respond because they are satiated and are not feeling deprived of something.

By definition, a motivating operation (MO) is a condition or physical state that alters the effectiveness of a reinforcer by making the reinforcer either more reinforcing (establishing operation, or EO) or less reinforcing (abolishing operation, or AO). It can evoke responses that produce that item or activity.

Motivating operations that are EOs involve a state of deprivation, meaning when one is deprived of a reinforcer or hasn’t gotten it in a while, the reinforcer’s effectiveness is increased:

• Food (hungry state)
• Drink (thirsty state)
• Rest (state of fatigue)

• Feeling full
• Recent access to a reinforcer

EXAMPLE

If someone is very hungry, then food is likely to be a reinforcer (the person is said to be in a state of deprivation). However, if someone just ate lunch and is full (person is in a state of satiation), then food is not likely to be a reinforcer.

EXAMPLE

If someone is eating salty foods, then a beverage is likely to be a reinforcer (deprivation). If someone just drank a glass of water, then a beverage is not likely to be a reinforcer (satiation).

EXAMPLE

If someone is tired (state of fatigue), then jumping on the trampoline is unlikely to be a reinforcer.

EXAMPLE

If someone is hot, then a fan blowing in their face is more likely to be a reinforcer than when the person is cold.

Your BCBA might ask you to contrive an EO to make a specific item more reinforcing to encourage the patient to give a particular response.

EXAMPLE

Consider the case in which Conner is hungry. Hunger or deprivation from food is the EO. When someone provides the S^D “What do you want?”, Conner’s motivation to reply by saying he wants a banana is increased because access to a banana is highly reinforcing.

In fact, Conner may be so motivated by the opportunity to receive a banana that the EO itself may evoke the response, “Banana,” and the behavior technician may not need to ask Conner what he wants. In this case, the antecedent leading to asking for a banana is not an S^D but is an EO.

EXAMPLE

In the following case, Conner is full because he just ate lunch. Now, the behavior technician is trying to get him to say that he wants a banana. The behavior technician asks him what he wants and he is unmotivated to respond, so he says nothing. This is an example of a banana losing its effectiveness as a reinforcer.

think about it

What could you do if you know you are going to try to teach a patient to respond to “What do you want?”

You may be asked to “contrive” or “capture” an EO in order to teach various skills.

EXAMPLE

You are working on colors with Claudia and she is painting a picture of a tree. Move the green paint out of reach. Because she needs the green paint to finish her painting, she will be more likely to ask you for the specific color.

Your BCBA will specify what type of antecedent – S^D or MO – you are using or contriving for each skill being taught.

term to know

Motivating Operation (MO)

A condition or physical state that alters the effectiveness of a reinforcer by making the reinforcer either more reinforcing (establishing operation, or EO) or less (abolishing operation, or AO) reinforcing