Watch the below video, or alternatively, read the transcript, then move on to Consolidation Exercise 1.
In our earlier lessons, we learned about how different types of consequences impact on behaviour.
We learned that consequences can reinforce, extinguish or punish a behaviour.
We know that if a behaviour that is reinforced increases in frequency. For example, if a child asks for a cookie, and that behaviour is reinforced, then they are more likely to ask for a cookie in the future.
However, you will probably have noticed in your own life that behaviour is not quite that simple.
A child may be more likely to ask their grandmother for a cookie than their mother. They may never ask a teacher or a stranger for a cookie.
Similarly, a teenager may curse or swear regularly when talking to a peer, but never does so in the presence of his or her parents.
The stimuli present in the environment before a behaviour also clearly impact on the occurrence of a behaviour.
Antecedents
We describe stimuli that occur before a behaviour as antecedents. Antecedent simply means ?what came before?.
From our previous examples, we know that different types of antecedents impact on the occurrence or non-occurrence of a behaviour.
When a behaviour is reinforced in the presence of a particular stimulus (or class of stimuli) and not reinforced in its absence, the behaviour will start to occur more often in the presence of that stimulus.
The Principle of Stimulus Control
A behavior that occurs more often in the presence of a certain antecedent stimulus (or class of stimuli), is referred to as being under stimulus control.
A behaviour comes under stimulus control because that behavior has been reinforced when that stimulus is present and not when it is absence.
Developing Stimulus Control ? Discrimination Training
To understand how stimulus control develops, we need to introduce two new terms ? the SD and the S-Delta.
The term SD stands for discriminative stimulus. A discriminative stimulus is the antecedent stimulus that has stimulus control over behavior because the behavior was reliably reinforced in the presence of that stimulus in the past. An SD signals to a person that a particular reinforcer is available.
A person, place, phrase or any form of detectable sensory stimuli can function as an SD.
The term S-Delta is another type of antecedent stimulus. It is an antecedent stimulus (or class of stimuli) in whose presence a behaviour has not been reinforced.
Let?s look at some examples:
A driver will stop their car when they see a red light. The behaviour of stopping is under the control of the red-light stimulus. In behaviour analysis, we would call this red light a discriminative stimulus for stopping.
Brian is a teenager. He regularly tells dirty jokes to his friends. When he tells them dirty jokes, his behaviour is reinforced. Brian does not tell dirty jokes to authority figures such as his teachers or parents. When he tried to do so in the past, the consequences were not reinforcing.
The presence of friends is an SD for telling dirty jokes. It signals to Brian that reinforcement is available.
The presence of authority figures is an S-Delta for telling jokes. It signals that reinforcement will not be available for that behaviour.
Our environments subject us to stimulus discrimination training every day. That is we learn to recognise SD?s and S-Deltas for a wide variety of behaviours and these can change over time.
Sometimes there is an instructor who is consciously trying to teach us something. This could be a parent, a teacher or a peer. But most of the time, our behaviour is reinforced, extinguished or punished without anybody consciously trying to do so.
Imagine that you could picking strawberries. You like strawberries, so seeing one is an SD for picking them. The reinforcer is eating them. But one day, you pick a green strawberry and you don?t like the taste. The behaviour of picking strawberries comes under the stimulus control of a strawberry?s colour. A red strawberry indicates that reinforcement is available. It is an SD. A green strawberry indicates that reinforcement is not available. It has become an S-Delta.
The Three Term Contingency
Stimulus Discrimination Training involves something called a Three-Term Contingency. In ABA, a contingency is effectively an ?if-then? statement that describes the likelihood of a certain behaviour and its consequences.
The three-term contingency attempts to describe how our environment affects our behaviour by looking at the relationship between antecedents, behaviours and consequences.
For example, let?s look at the behaviour of someone going to a restaurant:
Jim is walking down the street and sees a restaurant with a ?closed? sign. He does not enter that restaurant because there is a closed sign in the window. He walks further down the road and sees a restaurant with an open sign. He walks in and gets a meal.
In this scenario, we see two types of antecedent stimuli
- An closed sign (An S-Delta)
- An open sign (An SD)
The closed sign signals that reinforcement is not available (you can?t order food), while the open sign signals that reinforcement is available (you can order food).
The behaviours in this scenario are entering the restaurant and ordering food.
The consequence is eating food.?? In this case, this is likely to be a reinforcer.?
Summary
It is important for ABA professionals to understand the components of a three term contingency.
When we can describe the antecedents and consequences that affect a behaviour, we can identify why a behaviour is occurring and, potentially, how to address problems that a client might be experiencing. We?ll look at some of the ways we can do this in future modules, but for now, it is time to make sure you?ve mastered these concepts by completed the consolidation exercises.