Experimental Control Definition
 Is a predictable change in behavior (dependent
variable) that can be reliably produced by the
systematic manipulation of some variable
(independent variable)
Goal of Behavior Analysis
Experimentally determine the effects of
environmental manipulation on behavior
2. and demonstrate the effects can be reliably produced
1.
Internal Validity
 The extent to which an experiment shows that changes
in behavior are a function of the independent variable
 and not the result of uncontrolled or unknown
variables
Problem: Confounding Variables
 Variables known or suspected to exert an uncontrolled
influence on the dependent variable
 Effects must be evaluated and eliminated to
demonstrate experimental control
 Problem:
 May not know all of the confounding variables

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Time of day
Barometric pressure
Other unknown
Solution
 Eliminate as many uncontrolled variables as
possible
OR
 Hold constant the influence of all other
variables except the independent variable
Behavior
 Can be an individual phenomenon
 Can be a continuous phenomenon
 Assumes That:
 Behavior is determined
 Behavioral variability is extrinsic to the organism
Behavior as an Individual Phenomenon
 Examine a person’s interaction with the environment
 With ABA
 Strategy often based on within-subject (single-subject)
designs
Contrast: Dynamic / Continuous Behavior
 Behavior changes over time
 Requires continuous measurement over time
• Complete record of behavior as it occurs in context
• Often uses cumulative recorder types of
methodologies for recording
• Systematic repeated measurement is the “hallmark” of
ABA
Assumes
1. The occurrence of any event is determined by
the functional relations it holds to other events
2. Behavior is a natural phenomenon
3. Behavioral variability is the result of some
environmental influence
• In ABA
• Try to find out what it is
• Try to find interventions to change the
behavior
Components of Experiments in ABA
• Examine at least one
–
–
–
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Subject or participant
Behavior (dependent variable)
Setting
Treatment or intervention condition (independent
variable)
Research Question(s)
 Are statements about what the person wants to learn
about a behavior by conducting an experiment.
 Specifically: What are the effects of the independent
variable on the dependent variable
 Are always written down:
 Nothing exists until it is on paper (Brigham)
 Allows you to identify what you are examining
 Allows you to identify problems
 Allows you to create solutions
Many Different Designs
 Group Designs
 Single Subject
 Multiple Baseline
 Simultaneous Treatment
 Others
 Each has its advantages and disadvantages.
 Past research and experience helps you decide on the
type of design to use
Experiment using Groups
 Randomly selected pool of subjects from relevant
population
 Divided into experimental and control groups
 Pretest, application of independent variable to
experimental group, and posttest
Problem
 Group data may not be representative of individual
performance
 Some individuals within a group may stay the same or
decrease, while the improvement of others could make
it appear as overall average improvement
 To be most useful, treatment must be understood at an
individual level
 Individual can mean a group in an organization
Group Data Masks Variability
 Hides variability that occurs within and between
subjects
 Use statistical control to compensate
 Should not be a substitute for experimental control
 To control effects of any variable, must either hold it
constant or manipulate it as an independent variable
ABA
 Often uses single-subject designs
 Subject becomes its own control
 Measures of the subject’s behavior during each phase of the
study
 Allows you to compare variables as they are presented or
withdrawn during various conditions
May have Single or Multiple
Dependent Variables
• Single
• Only manipulation one variable
• Can often see clear results
• Multiple
• Still manipulate one variable
• Have multiple dependent variables
Reasons
 Gives data patterns that can serve as controls when
evaluating & replicating the effects of an independent
variable
 Allows you to assess the presence or extent an
independent variable may effect behaviors other than
the response class.
 Allows you to determine whether changes in behavior
of others occur during the course of an experiment
 Changes may explain changes in the subject’s behavior
Measurement Systems and Visual Analysis
• Observation & recording procedures must be
conducted in a standardized manner
• Standardization involves every aspect of the
measurement system
– Definition of the target behavior to scheduling of
observations
• Behavior analysts must develop skills in the
detection of changes in the level, trend, and
degree of variability in behavioral data
Independent and Dependent Variables
– Independent Variable
– The aspect of the environment that the experimenter
manipulates
– The researcher controls or manipulates this variable
independent of the subject’s behavior or any other
event
– Dependent Variable
– The behavior that changes as a result of changes in
the independent variable
– Is the thing you are observing
Experimental design
• Nonparametric study
– Independent variable is either presented or absent
during a time period or phase of the study
• Parametric study
– The value of the independent variable is manipulated
– Seeks to discover the differential effects of a range of
values
Fundamental Rule in Experimental Designs
• Change only one variable at a time
– Experimenter can attribute any measured changes to
a specific independent variable
– If investigating the effects of a “treatment package”
• Ensure that the entire package is presented or withdrawn
each time a manipulation occurs
• Allows you to make causal statements
Some Additional Rules
• Do not get locked into textbook “designs”
• Select & combine experimental tactics that best
fit the research questions
Steady State Strategies
– Repeated exposure of a given subject to a given
condition
– Try to eliminate or control extraneous influences on
behavior & obtaining a stable pattern of responding
before introducing the next condition
Baseline Data in ABA
• Serves as a control condition
• Does not imply the absence of intervention
– Absence of a specific independent variable
• Why examine?
– Allows you to observe a level of responding in the
absence of an independent variable
– Allows you to make comparisons when you
introduce an intervention
Benefits
• You can obtain descriptions of antecedent-behaviorconsequent correlations for the planning of an
effective treatment
– Valuable guidance in setting initial criteria for
reinforcement
– Baseline data may reveal the behavior targeted for
change does not warrant intervention
Types of Baseline Data Patterns
• Stable baseline (A)
• Ascending baseline (B and C)
• Variable baseline (D)
Types of Baseline Data Patterns
Example
Problem
 May be due to other variables
Need Verification
• Done by termination or withdrawal of the
treatment variable
Verification
Can use Replication
Conclusions
 Lots of aspects to experimental designs
 Need to make sure you know the strengths and
weaknesses of the designs you plan to use.
 Want to ensure your conclusions are based on solid
data.