Single Subject Research (Richards et al.) Chapter 8

Multiple Baseline Across Behaviors Design

Hargrove, P. M., Roetzel, K., & Hoodin, R. B. (1989). Modifying the prosody of a language-impaired child. Language, Speech, and Hearing Services in the schools, 20, 245-258.

Feature description

Type of Design Multiple baseline across behaviors

Goal of study Determine if a behaviorally based treatment can affect or modulate prosody of a child with language-impairments

Subject Six-year-old male receiving services for language dysfluencies

Setting The child’s home

Dependent variable The prosodic performance of the child

Independent variable Positive verbal feedback, token reinforcement, and a variety of cues along with specific training

Results and outcomes The performance by the subject on the probe items reached a 78% level of accuracy on two of behaviors and 67% on the third over the 18 training sessions that were implemented over a 9-day period

Across Behaviors DesignThe intervention was sequentially applied as the

criterion level of performance was met on the preceding target behavior.

Treatment was also discontinued with a target behavior once criterion was achieved.

Why using an across behaviors design for this study?

Permits performance on the three speech parts (subjects, verbs, objects) to be treated as separate variables.

The lack of covariance among the targeted responses before implementation of the training procedure strengthens the argument for internal validity.

Limitations of the StudyThe lack of identification of the training

components or combination of components that might have been responsible for changes (loose training).

The gains were not fully maintained. suggestions includes implementing a longer training phase, more vigorous criterion, or addition of a maintenance phase.

Multiple Baseline Across Subjects Design

Yoder, P. J., Yarren, S. F., Kim, K., & Gazdag, G. E. (1994). Facilitating prelinguistic communication skills in young children with developmental delay: II. Systematic replication and extension. Journal of Speech and Hearing Research, 37, 841-851.

This section is focused only on the first hypothesis among 3.

Feature description

Type of Design Multiple baseline across subjects

Goal of study Determine effectiveness of the modified milieu method for increasing intentional requests

Subject Four children between ages 21 and 27 months with mental retardation

Setting University-based early intervention program

Dependent variable Subjects’ behavior for intentional prompted and self-initiated requests and other intentional communication and preintentional signals

Independent variable Modified milieu teaching approach

Results and outcomes The modified milieu teaching approach is an effective method for increasing intentional questing and facilitating generalized communication in the subjects’ interactions with their mothers

Across subjects DesignThe researchers used abrupt changes in the level of

responding and slope of the data path as indicators of intervention effects rather than a specific criterion level to determine when to implement the intervention with the next subject.

Why using an across subjects design for this study?

It was easier to observe the effects of the intervention across subjects using this design.

Other designs (e.g., withdrawal design) would have been inappropriate. Once the requesting had increased, it is difficult to reverse this behavior in order to demonstrate a functional relationship.

Staggered introduction of the intervention helped build a strong case for verification and replication within the design itself.

Based on previous research conducted in the area of the milieu approach, it was expected before the study that there would be a functional relationship between the intervention and the subjects’ performance.

Limitations of the StudyIt was difficult to get the mothers into the clinic

for the intervention sessions. The effects of the generalization with the

mothers were not expected to be immediate due to the level of retardation of the students.

Suggestions: Future research should seek an extended study using control and experimental groups.

Although small groups are a strength of single subject research designs, such a small group (4 subjects) can affect degree of confidence in the generalizability of the intervention.

Multiple Baseline Across settings Design

Cushing, L. S., & Kennedy, C. H. (1997). Academic effects of providing peer support in general education classrooms on students without disabilities. Journal of Applied Behavior Analysis, 30,139-151.

Feature description

Type of Design Multiple baseline across settings

Goal of study Peer support provided by students without stabilities to students with disabilities will have positive effects on academic engagement and associated measures for the peers without disabilities

Subject Two 11-year-old students, one student without disabilities (Louie)and one with moderate intellectual disabilities (Leila)

Setting Suburban intermediate school with 1,100 students from diverse backgrounds; English, science, and social studies classes

Table ContinuedFeature description

Dependent variable Percentage of time academically engaged for Louie, defined as involvement in ongoing classroom activities and/or work-related assignments

Independent variable The peer support system of academic engagement that included participation with student with disabilities and training and/or supervision from special education and general education teachers

Results and outcomes The percent of time in which Louie was academically engaged increased during the periods he was serving as a peer support for Leila

Across settings DesignWhy using an across settings design for this study?

Using across settings design was more convincing, than using only one setting, to demonstrate a functional relationship between independent and dependent variables.

The multiple baseline design offered the advantages of providing intervention in all settings of need without having to withdraw treatment.

Limitations of the StudyBecause the sample of students was so

selective, the robustness of the findings requires systematic replication across a variety of students without disabilities.

The question that hasn’t been answered is that whether positive effects would occur for students who are already performing at high levels in general education classes.

Issues with Multiple Baseline Designs

The time and resources are sometimes problematic.

There may be no other behaviors, settings, or individuals available who are in need of the intervention.

At times, the need to identify an effective intervention as quickly as possible is very important. In this case, alternating treatments design may be appropriate.