Barkley’s Theory of ADHD
Laura M. Bimbo
November 3, 2004
DSM-IV ADHD
 Three core ADHD symptoms:
• Hyperactivity
• Impulsivity
• Inattention
 Three ADHD subtypes:
• Predominately Inattentive
• Predominately Hyperactive-Impulsive
• Combined Type
 Attention impairments have been thought to be
the central ADHD deficit
Why a new theory on ADHD?
 To date, most research is atheoretical
• Descriptive
• Exploratory
 DSM-IV criteria is descriptive only
– Observable behavior deficits only
 Current criteria for ADHD assumes that subtypes
represent similar deficits
– Individuals with ADHD do not show inattention in all
situations
(Barkley, 1997)
Subtypes = Different Disorders?
 Hyperactive-Impulsive type is a developmental
precursor to Combined type
• Preschool children vs. School aged children (Applegate et al.,
1995)
 Combined type = sustained attention and
distractibility
 High rates of ODD/CD comorbidity and other
poor outcomes (school suspensions, substance
use, etc.)
(Barkley, 1997)
Subtypes = Different Disorders?
 Purely Inattentive type usually appears at a later
age
 Inattentive type = deficit in speed of processing;
focused & selective attention)
 Symptoms = daydreaming, “spacing out”, “being
in a fog”, hypoactive, “sluggish cognitive tempo”
 Decreased rates of comorbidities
(Barkley, 2001)
Barkley’s Theory of ADHD
 Core impairment = Response Inhibition
 Due to abnormalities in the prefrontal cortex and
connections to other brain regions (striatum)
 Response Inhibition affects four intermediate
executive functions
 So, poor response inhibition + deficits in
executive functions = poor control
 Barkley also asserts that individuals with ADHD
don’t develop “future orientation and sense of
self across time”
Barkley’s Theory of ADHD
Response
Inhibition
Working
Memory
Self-Regulation
Of Affect/
Motivation/Arousal
Internalization
Of Speech
Motor Control/
Fluency/Syntax
Reconstitution
Response Inhibition
1.
2.
3.
Inhibiting the initial prepotent response to an
event.
Interrupting an ongoing response, permitting a
delay in the decision to respond or continue
responding
Protecting this period of delay from disruption
by competing events and responses
(interference control)
(Barkley, 1999)
Evidence for Poor Response
Inhibition in ADHD
 Behavioral Observations :
• Greater activity level (Luk, 1985)
• More talkative to others and self (Barkley, et al.,
1983; Copeland, 1979)
• More difficulty restricting behavior in laboratory
settings than other children (Luk, 1985)
• Less delay of gratification, less successful at
resistance-to-temptation paradigms (Campbell, et
al., 1994)
Response Inhibition
1.
2.
3.
Inhibiting the initial prepotent response to
an event.
Interrupting an ongoing response, permitting a
delay in the decision to respond or continue
responding
Protecting this period of delay from disruption
by competing events and responses
(interference control)
(Barkley, 1999)
Measuring Prepotent Responses
 Some studies have found no differences between
kids with ADHD and those without ADHD on
tasks measuring response inhibition
 Methodological problems:
– No immediate reinforcement within the task to
encourage prepotent responding
– If immediate rewards are provided, they are weak
reinforcers for this individual
– No history of reinforcement exists, so there is no
prepotent response for this individual
• (Barkley, 1999)
Evidence for Poor Inhibition of
Prepotent Responses
 Go-No-Go Paradigm (Barkley, 1997)
 Continuous Performance Test
– Errors of Commission
 Stop-Signal Paradigm
– Primary task of forced-choice letter discrimination
– When presented with a signal (tone), response is
inhibited
– Kids with ADHD show:
• Longer reaction times to signal
• Less inhibition of primary response
• More variation in their inhibition of primary response
Evidence for Poor Inhibition of
Prepotent Responses
Continuous Performance Test
– Errors of Commission
During a direct observation study, children
with ADHD interrupted more than control
children (Malone & Swanson, 1993)
Response Inhibition
1.
2.
3.
Inhibiting the initial prepotent response to an
event
Interrupting an ongoing response,
permitting a delay in the decision to respond
or continue responding
Protecting this period of delay from disruption
by competing events and responses
(interference control)
(Barkley, 1999)
Evidence for Difficulty
Interrupting Ongoing Responses
 Stop Signal Paradigm
 Wisconsin Card Sorting Task (WCST)
– Involves shifting to a more effective response pattern
when feedback indicates that the ongoing response is
incorrect
– Children with ADHD often perseverate, even when
feedback is given (Barkley, 1997)
– Interestingly, first-degree relatives of individuals with
ADHD are more prone to perseverations
Evidence for Difficulty
Interrupting Ongoing Responses
On an information processing task,
children with ADHD were less likely to
change their response style (i.e. slow
down) after corrective feedback
Card Playing Task
– Children with ADHD bet on more trials than
control subjects, despite increased liklihood of
being incorrect
Response Inhibition
1.
2.
3.
Inhibiting the initial prepotent response to an
event
Interrupting an ongoing response, permitting a
delay in the decision to respond or continue
responding
Protecting this period of delay from
disruption by competing events and
responses (interference control)
(Barkley, 1999)
Evidence for Poor Interference
Control
 Stroop Color-Word Test
– Subjects with ADHD (and their siblings) perform
poorly when responding to the color of words rather
than reading the words (Barkley, 1997)
– Differences are also found when comorbid conditions
are controlled for
– Neuroimaging studies have shown that the right
prefrontal region is involved in the performance of this
task
Barkley’s Theory of ADHD
Response
Inhibition
Working
Memory
Self-Regulation
Of Affect/
Motivation/Arousal
Internalization
Of Speech
Motor Control/
Fluency/Syntax
Reconstitution
Working Memory
Holding information in mind,
manipulating or acting on the information
Hindsight (retrospection)
Foresight (prospection)
Empirical evidence in kids with ADHD:
– Digit span (especially backwards)
– Mental arithmetic
Barkley’s Theory of ADHD
Response
Inhibition
Working
Memory
Self-Regulation
Of Affect/
Motivation/Arousal
Internalization
Of Speech
Motor Control/
Fluency/Syntax
Reconstitution
Self-Regulation of AffectMotivation-Arousal
Emotional self-control
Social perspective taking
Ability to express emotions internally
Intrinsic motivation directed at long-term
goals
Empirical evidence in kids with ADHD:
– More negative and emotional peer interactions
– Impairment in persistence of effort
Barkley’s Theory of ADHD
Response
Inhibition
Working
Memory
Self-Regulation
Of Affect/
Motivation/Arousal
Internalization
Of Speech
Motor Control/
Fluency/Syntax
Reconstitution
Internalization of Speech
 Self-directed speech (“private speech”)
 Formulating rules and plans to solve problems
 Internal reflection, description, questioning,
instructing
 Create internal rules for governing behavior
 Empirical evidence in kids with ADHD:
– Less compliant with verbal commands
– Immature self-directed speech
– Develop internal speech at a later age
Barkley’s Theory of ADHD
Response
Inhibition
Working
Memory
Self-Regulation
Of Affect/
Motivation/Arousal
Internalization
Of Speech
Motor Control/
Fluency/Syntax
Reconstitution
Reconstitution
 Ability to create complex and novel behavior
sequences in order to attain future goals
(generativity or fluency)
 Involves analysis and synthesis
 Empirical evidence in kids with ADHD:
–
–
–
–
Ideational fluency (Barkley, 1999)
Verbal fluency (esp. FAS)
Less info and organization in stories (Tannock, 1996)
Less creativity during free play (Funk, et al., 1993)
Barkley’s Theory of ADHD
Response
Inhibition
Working
Memory
Self-Regulation
Of Affect/
Motivation/Arousal
Internalization
Of Speech
Motor Control/
Fluency/Syntax
Reconstitution
Motor Control/Fluency/Syntax
Deficits in response inhibition and the four
executive functions lead to impairments in:
–
–
–
–
–
Control
Timing
Persistence
Flexibility
Goal-directed actions
Motor Control/Fluency/Syntax
Barkley asserts that these deficits manifest
in ADHD children through:
– Ability to adapt to new information
– Ability to predict what will happen
– Ability to generate responses to future info
ADHD = “nearsighted when it comes to
time” or “time blindness”
(Barkley, 1999)
Motor Control/Fluency/Syntax
Problems with sustained attention result
from a limited intrinsic motivation for
future goals
Effectiveness of stimulant medications:
– Due to enhancement of inhibitory
mechanismsimproved four areas of
executive functioning
Barkley’s Theory:
Limitations
 Are difficulties in inhibition a result of ADHD or
comorbid problems such as aggression, ODD, &
learning disabilities
 How much affect does response inhibition have
on the 4 executive functions in the model?
 How much does each executive function
contribute to motor control?
 Can the 4 executive functions be further reduced?
Barkley’s Theory:
Limitations
 Do stimulant medications differentially affect
each of the 4 executive functions?
 Is there some hierarchical organization to the
executive functions?
 Can this model be used to dissociate Inattentivetype ADHD from the other types?
 Does socialization affect the development of
these executive functioning?
 What gender and ethnic differences exist in the
development of these executive functions?
Barkley’s Theory:
Treatment Implications
Basis of treatment Environmental
modifications
No delay between response and outcomes
Breaking down tasks into smaller
components
Key conceptPoint of performance
Barkley’s Theory:
Treatment Implications
Place key information at the point of
performance:
–
–
–
–
Provide external rewards/motivation
Minimize distractions
Put clock on student’s desk
Display rules at point of performance