In previous modules, we?ve looked at some of principles and procedures of ABA. We?ve looked at differential reinforcement, shaping and stimulus control as well as various prompting and fading procedures. We?ve talked about chaining and the use of task analysis.
In this module we are going to examine some commonly used teaching formats. The first format we will look at is discrete trial teaching (DTT).
Discrete Trial Teaching (DTT) is one of the most well-known and researched ABA teaching procedures. DTT involves breaking complex skills down into discrete sub-skills, teaching them intensively and later re-combining them into the complex skills.
Discrete trials are called ?discrete? because each teaching trial has a clear beginning and end. A trial is based on the three-term contingency and has five parts:
- The teacher obtains a readiness response from the learner
- The teacher presents a target antecedent SD (and a prompt if scripted as part of the teaching plan)
- The learner responds
- The teacher provides a consequence (reinforcement for correct responses or a correction)
- Then there is an intertrial interval
Let?s look at these steps in a little more detail.
Readiness Response
The purpose of obtaining a readiness response is simple: If a learner is not attending to the teacher, then they are unlikely to attend to the target SD. What constitutes a readiness response depends on the learner.
For some learners, you might recognise a readiness response by the learner initiating eye contact. In other cases, they might orientate themselves towards you or the teaching materials. In some cases, you might ask the learner ?Are you ready?? and if they responded ?Yes?, you would know that they were ready for teaching.
Antecedents
A skill acquisition plan will tell you what the target SD should be. For example, if you were teaching a young child to identify different types of animals, the skill acquisition plan might direct you to lay out an array of three pictures of animals and then direct you to present the instruction ?Find the sheep?.
In some cases, it might also state what type of prompt to use. For example, it might instruct you to use a gestural prompt or a positional prompt. If using a gestural prompt, you would point to the correct picture AFTER you delivered the instruction. In some cases, you might be instructed to use a more general prompting procedure such as most-to-least prompting or least to most prompting.
Behaviour
The skill acquisition plan will also let you know what response is required. In our current example, that would involve the learner pointing to the sheep (a listener response). However, other responses you could target include tacts, echoics and intraverbals.
Consequence
The type of consequence a teacher provides depends on the learner?s response. If the learner carried out the target response at the target prompt level, then they would receive some form of reinforcement. This could be praise, a token or some other form of positive feedback.
If the learner did not carry out the target response, then you would carry out a correction by re-presenting the SD (i.e. the instruction) and then prompting the correct response. For example, if the learner had not pointed to the sheep when you used a gestural prompt, you might use a more intrusive prompt (e.g. an elbow prompt or hand over hand prompt) to make sure they pointed to the correct item.
While you might provide neutral feedback after a corrected response, you do not reinforce it. This is because we are using differential reinforcement (reinforcement and extinction). In our example, the target behaviour we were reinforcing was pointing to a picture of a sheep when asked to do so and provided with a gestural prompt. All responses that require more intrusive prompts are placed on extinction.
The Intertrial Interval
Traditional DTT typically involves presenting many opportunities to respond in a short period of time. The time between two learning opportunities is called the inter-trial interval. This is usually 3-5 seconds long or in cases where the learner gains access to a tangible reinforcer, however long it takes for the learner to meaningfully engage with the reinforcer.
During this time, the teacher records data (whether the learner got the trial correct or not, or the level of prompting required), and prepares for the next trial. In our example, this might mean that the array of animals was rotated or some pictures might be substituted.
After the interval, the next trial is presented.
Embedded Discrete Trial Teaching
Traditional DTT is often carried out in schools or clinics at a table or on a tablet. An alternative way of carrying out DTT is using embedded discrete trial teaching. When embedding a discrete trial, you follow all of the steps we previously outlined but do so within a naturally occurring routine or activity. For example, for some young learners, you might teach them to identify animals by using story books and videos. You would still present the instruction, the prompt and the consequence in a similar fashion, but it would be during typically occurring activities rather than while sitting at a desk etc.
Shaping, Developing Stimulus Control, Prompting and Fading
The DTT format can incorporate procedures such as discriminating training and shaping.
For example, if you were teaching if using shaping to teach somebody to tact popcorn, a DTT procedure might look like:
- Antecedent: Present a picture of popcorn to Tom and say ?What is it?
- Behaviour: Tom will say ?Puh?
- Consequence:
- If correct, provide praise on an Fr1 schedule and a token on a Vr2 schedule.
- If incorrect, provide repeat and the antecedent and provide an echoic prompt
In this example, once Tom had achieved the mastery criteria 90% twice over two sessions of 20 learning opportunities, the next target was:
Antecedent: Present a picture of popcorn to Tom and say ?What is it?
- Behaviour: Tom will say ?Pop?
- Consequence:
- If correct, provide praise on an Fr1 schedule on a Vr 3 schedule.
- If incorrect, provide repeat and the antecedent and provide an echoic prompt
Each time the criteria was met, the DTT procedure would change to a more advanced approximation, until the terminal goal was achieved (i.e. saying Popcorn).
Let?s look at another example, that highlights how stimulus control can be achieved through discrimination training as part of DTT:
In this scenario, Tom?s RBT is teaching him to identify different fruits. He has already mastered three (apple, orange and pear). The current teaching procedure is:
- Antecedent: Present an array of three fruits (2 mastered and 1 strawberry). Give the vocal instruction ?Find _____?. Intermix 10 opportunities to find the strawberry and 10 to find mastered fruits
- Behaviour: Tom will point to the correct fruit
- Consequence:
- If correct, provide praise on an Fr1 schedule and a token on a Vr3 schedule.
- If incorrect, provide repeat and the antecedent and provide a gestural prompt
As you can see, in this teaching procedure the idea is to bring the behaviour of pointing to the strawberry under the stimulus control of the instruction ?Find the strawberry?. If told to point to the strawberry and Tom responds by pointing to the strawberry, he receives reinforcement. If told to point the strawberry and he points to the pear, he does not. If told to point to the apple and he points to the strawberry, he does not receive reinforcement.
In the above example where Tom was learning to discriminate fruits, the DTT procedure only involved prompting as part of the correct procedure, however prompting can also be included within such procedures. Let?s look at how we might do that:
- Antecedent: Present an array of three fruits (2 mastered and 1 strawberry). Give the vocal instruction ?Find _____?. Intermix 10 opportunities to find the strawberry and 10 to find mastered fruits
- Prompt: Gestural prompt for instructions to find a strawberry
- Behaviour: Tom will point to the correct fruit
- Consequence:
- If correct, provide praise on an Fr1 schedule and a token on a Vr3 schedule.
- If incorrect, provide repeat and the antecedent and provide a hand over hand prompt
In this example, the discrimination training procedure incorporates prompting. Tom is given a gestural prompt to find the correct response. The correction procedure provides a more intrusive prompt i.e. a hand over hand prompt.
The prompt would be removed if Tom met the mastery criteria. The mastery criteria is a rule for how to decide when a particular skill or a particular phase of a skill acquisition program is mastered based on the accuracy of a learner?s performance
For example, in this case, the learner is expected might be expected to get 90% of 20 trials correct over 2 consecutive days. When that happened, the prompt would no longer provided and the teaching procedure would change to the below:
- Antecedent: Present an array of three fruits (2 mastered and 1 strawberry). Give the vocal instruction ?Find _____?. Intermix 10 opportunities to find the strawberry and 10 to find mastered fruits
- Behaviour: Tom will point to the correct fruit
- Consequence:
- If correct, provide praise on an Fr1 schedule and a token on a Vr3 schedule.
- If incorrect, provide repeat and the antecedent and provide a gestural prompt
As you can see, in order to receive reinforcement, Tom now needs to point to demonstrate the target behaviour without the gestural prompt if his behaviour is to be reinforced. The default correction prompt is now a gestural prompt rather than a physical prompt because we know that he can already carry out the behaviour with a gestural prompt.
Maintenance
As you may remember from earlier lessons, in ABA our goal is for behaviors to occur under naturally occurring schedules of reinforcement, but when teaching a new skill, the skill is acquired more easily with thick schedules of reinforcement. When teaching a new type of skill to somebody during DTT, we typically start off with thick schedules of reinforcement, but over time we alter the reinforcement schedule to thinner schedules of intermittent reinforcement. This increases the probability of skills maintaining over time.
Generalisation
The spreading of the effects of intervention to outside of the intervention is known as generalisation.
Stimulus Generalisation
One type of generalisation is stimulus generalisation. Imagine going to a shop to buy a t-shirt. There will be many different types of t-shirt ? different colours, different sizes and different styles. But you can still identify a t-shirt and discriminate it from other items of clothing like sweaters or shirts.
You?ve never been taught to learn the a ripped, purple and black t-shirt is a t-shirt, but you?ve generalised from the examples you?ve been taught about in the past. You know (even you can?t quite find the words to describe it) that the common features of t-shirts are that they are short-sleeved casual tops that have the shape of a T when spread out flat.
We know that stimulus generalisation when a behaviour occurs in response to untrained or new stimuli or examples of stimuli.
Response Generalisation
When you meet somebody and they say ?Hi? to you, how do you respond?
Some days you might say ?Hi? back. On other days you might say ?Hello? or ?Hey, how are you??
While you might have been explicitly taught to say ?Hello? to people when you were a toddler, most responses you make to the stimulus of somebody saying ?Hi? have not been trained or taught.
You?ve placed many different forms of greeting or responses to greeting into a single class. They are united by their function. You know (even if you don?t need to think about it) that any of the responses is a response that you can use when somebody says ?Hi?. This is an example of response generalisation.
We know that response generalisation has occurred when somebody learns a skills and then performs a variation of it in response to a similar situation.
Discrete Trial Teaching and Generalisation
When using discrete trial teaching, there are some tactics we adopt to ensure appropriate stimulus and response generalisation.
Teaching using multiple exemplars
For example, if you were teaching a child to tact ?dog?, you would use lots of examples of dogs ? terriers, huskies, greyhounds and chihuahuas. You might even include cartoon dogs from Scooby Doo or Paw Patrol and make sure that the dog exemplars feature dogs in different positions and different contexts.
The greater the variety of exemplars we use during training, the more likely it is that stimulus generalisation will occur.
Vary Your Instructions
If teaching somebody the intraverbal responding to personal information questions, you might vary the way you ask the question.
For example two functionally equivalent examples of the same question would be ?What?s your name?? and ?Who are you?? Likewise, ?How old are you?? and ?What age are you?? both have the same appropriate response.
If teaching listener discrimination, saying ?Find the girl?, ?Point to the girl? and ?Where is the girl?? all require the same response.
The chances of the learner responding the novel versions of the same instructional increase if you teaching using multiple versions of the instructional SD.
Teach with Different People and Environments
As with instructions and materials, teaching across multiple environments and people increases the probability of stimulus generalisation. This is why it is important that when using DTT, you make certain that learning opportunities are provided by different RBTs in different situations.
Tips for Good DTT
Delivering the Antecedent
- Always ensure that you get a readiness response before delivering the target SD to the learner. A stimulus is only a stimulus when somebody is aware of it
- Use an instructional tone ? this is generally very slightly louder than your normal conversational volume
- Use clear and concise language that matches a learner?s listening skills ? When we talk about being clear, we mean saying something like ?Come here? rather than ?Comeere?. When talk about being concise and matching the learner?s level, we mean that you should avoid confusing a learner by providing more information than they are able to process. Saying ?touch the shoe on the table please? might be appropriate for learners who have good listening skills, but for those with emerging listening skills saying ?Touch shoe? may make it easier for them to understand you
- Only provide the instruction once ? If you?ve already observed a readiness response, then you know the learner has already heard you. Continually repeating an instruction can accidentally shape up undesirable behaviors
Delivering Prompts
- If using a stimulus prompt, ensure that it is ready before presenting an instruction to a learner.
- If using a response prompt, ensure that you present it immediately AFTER delivering an instruction. If you start to deliver it at the same time as the SD, the learner will not attend to the SD and the target behaviour will not come under the control of the target SD
Delivering Consequences
- If providing reinforcement, do so immediately after the target behaviour occurs. The closer reinforcement occurs in relation to the behaviour, the stronger the relationship between the target behaviour and gaining reinforcement will be.
- Only record data AFTER you provide reinforcement
- If a behaviour is incorrect and you need to provide a correction, always remember to repeat the SD before prompting the target response
- Remember not to reinforce the corrected response
During the Intertrial Interval
- Remember to record data during the intertrial interval
- If you are using teaching materials such as pictures etc., use the intertrial interval to alter them by substituting pictures or rotating an array etc.
Other Tips
- Avoiding providing inadvertent contextual cues. Sometimes behaviour technicians subconsciously provide the learner with some indication of the correct response. For example, if teaching a listener skill that involves an array, they might keep glancing at the correct item. If asking a learner to match an item, they might hold a card over the duplicate item.
- When rotating an array, make certain that you do not have positional biases. Sometimes, people will find themselves placing the target stimulus in the same position (e.g. on the right or in the centre)
- Make sure that your reinforcers are effective. Remember, the goal of DTT is to build an association between the target behaviour and reinforcement. If there is no motivating operation in place for the item you are using as a reinforcer, then learning may not occur
Advantages of DTT
- DTT isolates skills and teaches them in the smallest necessary components. This maximises the chances of learners achieving success when learning complex concepts
- It can be highly structure which helps make contingencies as clear as possible
- While structured, it can be flexible and adapted to teach a wide variety of skills
- It can be used in a variety of different environments with individuals who have different levels of functioning
- Progress occurs at a learner?s rate of mastery
- In addition to teaching the target skills it also teaches co-operation and interaction with instructors in a rewarding fashion
- The format facilitates the collection of reliable data which can be used to analyse problems
- It also facilitates consistency across teachers
Disadvantages of DTT
- DTT is teacher lead rather than learner led. This can make it more challenging for some learners
- Generalisation may not occur if the teacher is not skilled and does not program for generalisation.
- Some learners may find inflexible versions of DTT stressful or otherwise aversive