1. 1
System of Least Prompts
Chain Task
Instructional Objective:
When given the verbal direction “Open a can of (content)”, Ted will perform with
95% accuracy for 2 consecutive sessions over 2 consecutive days all the steps in the task
analysis, when reinforced on a VR-3 and respectively on a FR-22 schedule.
Task Sequence and Task Analysis:
The instructional framework will be a total task presentation, when the
interventionist will give Ted the opportunity to perform independently each step of the
task analysis. In order to break this activity into discrete behaviors, I performed the entire
task for myself and noted down the steps that I usually carry out in order to open a can.
The 22 steps of the task analysis are described on page 8.
Instructional Arrangement: 1:1.
Description of subject and prerequisite behaviors:
Ted is a 14 year-old male identified with mild intellectual disabilities and
impairment in fine motor coordination. Ted will be screened in order to assess
prerequisite behaviors. Ted should display the ability to (a) to recognize and respond to
stimuli used as discriminative stimuli during the intervention, (b) voluntary motor control
to perform the task, (c) to adequately perform the target skill, i.e. gross motor abilities to
stand, walk, grasp, pull, and turn his wrist, (d) to remain on task for up to 30 minutes
without interruption, and (e) to have an instructional history with a contingency
reinforcement system.

2. 2
Target Stimuli/Materials:
Two sets of materials will be used during the intervention, one for the student to
use, and one for the interventionist. The materials involved in performing the task will
vary, e.g. cans of different sizes, color, with various contents, different can openers,
different sinks, different trainers, different cabinets and drawers from different settings,
such as classroom, school home economics room, learner’s home, etc.
Probes: A number of at least 3 probe sessions will be conducted or until a stable trend
will be established. The teacher will deliver the task direction “Ted, open a can of
(content)” and wait 5 seconds for the student to initiate a response and 8 seconds for the
student to complete the response. If Ted does not perform the correct response, he will be
asked to turn around, and the teacher will perform the step for him. Then, Ted will be
asked to attend to the discriminative stimulus, i.e. the completed previous step, and he
will be given 5 seconds to initiate and 8 seconds to complete his response. Only correct
or incorrect responses will be recorded. Correct responses will result in delivery of the
reinforcer, and incorrect responses will be interrupted.
Procedure Description:
Procedure: A system of least prompts (SLP) will be used to teach Ted to open a can.
Prompt Hierarchy: The SLP procedure will use a 4 level hierarchy of prompts, arranged
from least intrusive to most intrusive amounts of assistance. The last level of prompt in
the hierarchy is a controlling prompt, one that ensures correct responses for each step of
the task analysis. The prompt hierarchy consists of the next levels of prompts:
(1) independent or no assistance;
(2) verbal directions;

3. 3
(3) model and verbal directions;
(4) full physical prompt and verbal directions.
Discriminative Stimuli: The discriminative stimulus for the first step in the task analysis
is the task direction delivered by the teacher/interventionist “Ted, open a can of
(content)”. For the remaining 21 steps of the task analysis, the completion of the previous
step will represent the discriminative stimulus for the next step in sequence. The target
stimulus will be present(ed) at each level in the prompt hierarchy.
Specific Active Attentional Cues: The teacher will use specific active attentional cues to
ensure that the student will attend to the critical features of the discriminative stimulus,
such as “Ted, what are you supposed to do?” for step 1, when Ted is required to verbally
respond “(I am supposed to) open a can of (content)”; “Ted, look in the drawer. Where
are you going to look?” for step 7, when Ted is required to verbally answer “(I am
looking for) the drawer”; “Ted, look for the trash can” for step 20, to which Ted is
required to answer “(I am looking for) the trash can”; or simply “Ted, what is next?”,
when Ted is required to verbally describe the next step in sequence.
Prompt Interval: After the presentation of the discriminative stimulus, the teacher will
wait 5 seconds for the student to initiate the target response.
Response Interval: Upon initiation of the correct target response, the teacher will wait 8
seconds for the student to complete his response on all steps of the task analysis, except
step 14, when the teacher will wait 30 seconds for the student to cut the lid of the can.
Possible Student Responses: (1) unprompted corrects, also known as correct
anticipations, are correct responses initiated by the student within 5 seconds, before the
trainer delivers the prompt at a certain level; (2) prompted corrects, also known as correct

4. 4
waits, are correct student responses given after the prompt has been delivered; (3)
unprompted incorrects, also known as nonwait errors, are incorrect student responses
exhibited before the prompt was presented, that is within 5 seconds from the presentation
of the target stimulus or completion of the previous step in the task analysis; (4)
prompted incorrects, also known as wait errors, are incorrect student responses performed
after the prompt has been presented; and (5) no response errors are recorded when the
student does not perform any response after the prompt has been presented. Unprompted
and prompted incorrect responses (errors) will be coded as topography (the shape of
student’s behavior is incorrect), duration (student’s response exceeds 8 or 30 seconds, as
previously established), or sequence (student initiates an out of sequence behavior, that
is, a step that does not follow the order of the task analysis steps) errors. Only correct
independent responses will count toward final criterion.
Reinforcer: All correct responses will result in descriptive verbal praise delivered at each
level of the prompt hierarchy on a continuous reinforcement schedule (CRF) until the
student performs independently 60% unprompted correct responses, and on a variable
ratio of every 3 correct responses schedule (VR-3) until the student performs 95%
independent correct responses for one session, after which he will be reinforced on a
fixed ratio of every 22 correct responses (FR-22). If Ted’s performance decreases after
one session of 95% correct responses when reinforced on a VR-3 schedule, the
interventionist will return to the VR-3 schedule of reinforcement until first part of final
criterion will be reached again. The back-up reinforcer will be delivered at the end of the
22 steps of the task analysis, namely the opportunity to consume the content of the
opened can.

5. 5
Incidental Information: Following each correct response, the teacher will include in the
consequences, i.e. s/he will add to the descriptive verbal praise, non-targeted information
related to the task, information that will remain consistent for each step of the task
analysis throughout the intervention. For example, after Ted will correctly touch can (step
2), the teacher will say “Good job, Ted. This is a can of (content). A can is made of
metal”; following a correct response on step 6, opening the drawer, the teacher will say
“Yes, this is the drawer under the counter. Drawers can also hold cooking and eating
utensils”, etc.
Error Correction: Unprompted incorrect responses will result in the teacher interrupting
the response, reminding the student that he has to wait if he does not know the correct
response, and delivering the next, more intrusive, level of prompt in the prompt
hierarchy. Prompted incorrect responses will result in the teacher interrupting student’s
response, saying “No”, and delivering the next level of the hierarchy. No responses will
result in the teacher delivering the next level of prompt. If no responses occur or the
student opposes resistance after the presentation of the controlling prompt, i.e. the final
level of prompt in the hierarchy as the most intrusive prompt, the teacher will avoid eye
contact with the student and will not attend to the student for 5 seconds.
Training sessions: The teacher will deliver the task direction and the specific active
attentional cue “Ted, open a can of (content). What are you supposed to do?”. Upon
student’s correct verbal response “(I am supposed to) open a can of (content)”, the
teacher will wait 5 seconds for the student to initiate the first step in the task analysis, i.e.
open the cabinet door. If the student will initiate the target response within 5 seconds, the
teacher will wait 8 seconds for Ted to complete his response and record an unprompted

6. 6
correct response if he does open the cabinet door within 8 seconds from initiation and
deliver the reinforcer and incidental information, or an unprompted incorrect if Ted does
not complete the correct behavior within 8 seconds. If Ted does not independently initiate
the correct response within 5 seconds, the teacher will deliver the next more intrusive
prompt in the hierarchy, i.e. the verbal description of the step, the task direction, and will
wait 5 seconds for the student to initiate a correct response. If Ted will initiate the correct
response within 5 seconds and complete it within 8 seconds, the teacher will record a
prompted correct response and will deliver descriptive verbal praise and incidental
information for that step. If Ted will initiate an incorrect response, the teacher will
interrupt his response, deliver the next prompt in the hierarchy and the task direction.
Also, if Ted does not initiate any response within 5 seconds, the teacher will deliver the
the next prompt in the hierarchy, that is, the teacher will model the correct response on
his set of materials while describing the step “Ted, watch me. You are supposed to open
the cabinet door”, followed by the delivery of the task direction. If the student will
initiate the correct response within 5 seconds after the prompt and complete it within 8
seconds from initiation, a prompted correct response will be recorded at level 3 of the
prompt hierarchy. If the student does not initiate a response within 5 seconds from the
presentation of the task direction, complete the correct response within 8 seconds from
initiation, or initiates an incorrect response, the teacher will interrupt the incorrect
response, deliver the task direction again, and the next prompt level in the hierarchy, i.e.
full physical prompt. The teacher will perform the task with the student, hand-over-hand,
and record a prompted correct response for the 4th level of the prompt hierarchy. If Ted
will oppose resistance, a no response will be recorded and the teacher will avoid eye gaze

7. 7
and will not attend to the student for 5 seconds. Then, the teacher will perform the step
for the student, on Ted’s set of materials, and wait 5 seconds for Ted to independently
initiate the correct response for the next step in the task analysis. Instruction on each step
will continue in this manner, the teacher delivering descriptive verbal praise and
incidental information for each correct response or interrupting the incorrect response and
delivering the next level of the prompt hierarchy until Ted will complete all steps in the
task analysis. Only independent unprompted correct responses will count toward final
criterion.
Data Collection Methods:
An event recording data collection sheet will be used to record information about
the student and procedural data; the five types of student responses will be recorded by
putting a mark in the appropriate column and row (in the errors column a T will be
recorded for a topographical error, a D for a duration error, a S for a sequence error, or a
O for other behavior); and a summary section with a total number and percent of each
type of response.

8. 8
Task Analysis for Opening a Can:
1) Open cabinet door.
2) Touch can.
3) Pick up can.
4) Close cabinet door.
5) Place can on the counter.
6) Open drawer (under the counter).
7) Touch can opener.
8) Pick up can opener.
9) Close drawer.
10) Place can opener on the counter.
11) Detract (open) can opener handles.
12) Place the cutting top (blade) of can opener on the edge of can so that the blade
touches the lid of the can.
13) With left hand, squeeze the can opener handles on the edge of the can until the
blade of can opener penetrates the lid of can (the blade gets into the can).
14) With right hand, turn forward the rotating key of the can opener while continuing
to squeeze its two handles with left hand. Continue turning the can opener key
until the lid is cut off completely.
15) Switch can opener to right hand.
16) Position the narrow top (the hook) of can opener on the lid of can.
17) Press the hook against the edge of the lid until part of lid enters the can and the
other part rises on the opposite side.
18) With left hand, grab the lid from the raised edge.
19) Take lid off can.
20) Place lid into trashcan.
21) Place can opener in sink.
22) Stop.