Fluency Mid-Term Test - Part Two: Theories and Models of Stuttering

Recovery & persistence of stuttering

• 70-80% of children recover unassisted 

• 20-30% of children’s stuttering will persist

Early theories of the causes of stuttering

Francis Bacon (1561-1626) 

• tongue stiff & frozen in act of stuttering 

Treatment

• tongue should be thawed with hot wine 

Johann Friedrich Dieffenbach (1792-1847)

• during stuttering the tongue ‘clave to the roof of the mouth’ 

treatment 

• cutting triangular wedge from back of tongue with scissors 

• performed >250 surgeries without anesthesia

Psychological theories of stuttering

• Psychoemotional theories 

• Psychobehavioural theories 

• Psycholinguistic theories

Psychoemotional theories

• Psychoanalytic theory 

• Temperamental & emotional processes

Psychological traumas (Psychoanalytic)

• psychoanalytic theories now refuted, but contributed to beliefs that

• stutterers are neurotic 

• parents are implicated 

• beliefs spread to medicine, social work & public knowledge 

• stutterers were routinely referred to psychotherapists for treatment

Temperamental & emotional processes

• CWS may exhibit increased reactivity & decreased regulation 

• linked with increased stuttering frequency/severity 

Bidirectionality? 

• temperament is a genetically influenced set of individual differences 

• experiences with stuttering probably not solely responsible for differences 

• emotional reactions may develop due to stuttering

Psychobehavioural theories

• Diagnosogenic theory 

• Approach-avoidance conflict theory 

• Two-factor theory

Psychobehavioural theories

• Stuttering acquired as behavioural response to some form of reinforcement 

• Pavlov – classical conditioning 

• Skinner – operant conditioning

Pavlov – classical conditioning

Skinner – operant conditioning

Diagnosogenic theory

• Wendell Johnson (1906-1965) 

• ‘Stuttering begins not in the child’s mouth but in the parent’s ear’ 

• stuttering caused by parents’ misinterpretation of their child’s normal disfluencies 

• reactions of parents & child result in worsening of speech, leading to stuttering

• tested in 1939 ‘Monster study’ 

• 12 children – 6 in ‘negative comments’ group developed symptoms of stuttering 

• 2001 University of Iowa made public apology and paid ~ 1 million $ to the 6 children 

• none of them developed permanent stuttering

• profound influence on treatment 

• children: indirect, focus on parent counseling & parent-child interactions 

• adults: reorientation of person’s perspective on the problem 

• disproven as disfluencies in CWS differ from those in NFC

Approach-avoidance conflict (Sheehan, 1953)

Stuttering due to conflict between approach (= drive to speak) & avoidance (= fear of speaking)

Two-factor theory (Brutten & Schoemaker, 1967)

• Core stuttering behaviours result from classical conditioning 

• anxiety to speaking situations 

• Secondary behaviours reinforced by operant conditioning 

• successfully prevent or end stuttering moment

Summary of Psychobehavioural theories

• assume that anyone may acquire stuttering under correct circumstances 

• concerned with observable phenomena 

• offer explanations for individual moments of stuttering rather than initial onset 

• cannot account for findings from genetic studies 

• therapy influence: what is learned can be unlearned

Psycholinguistic theories

• Covert repair hypothesis 

• EXPLAN theory

Psycholinguistic theories - Covert repair hypothesis

• Postma & Kolk (1993) 

• Stuttering results from self-monitoring of inner speech 

• Covert repairs made to phonetic plan before errors occur 

• phonological encoding deficit or hyperactive monitoring? 

• But inconsistent evidence on phonological abilities of PWS

Psycholinguistic theories - EXPLAN theory

• Howell (2004) 

• EXecution of linguistic plan cannot take place until its PLAN has been completed 

• Asynchrony occurs if motor execution rate exceeds linguistic planning capacity

Psycholinguistic theories - Summary

• Provide insights in nature of disfluent speech 

• Help account for various loci of stuttering & relationship between stuttering and language 

• Do not offer broad explanations of stuttering etiology, onset, social-emotional aspects or ameliorating conditions

Psychological theories

Conclusion 

• Psychoemotional, psychobehavioural & psycholinguistic factors can contribute to stuttering 

Clinical management 

• reduce anxiety 

• identify stimulus cues that trigger stuttering 

• slow down speech

Biological theories

• Genetic perspectives 

• Neurological perspectives

Genetic perspectives

Family studies 

• familial stuttering in 30-60% of PWS but only 10% in FS 

• genetic mechanisms may involve transmission of genes for predisposition of stuttering & genes that prevent natural recovery from stuttering

Twin studies

• higher concordance of stuttering in identical twins (in 2/3 of pairs) 

• but stuttering may occur in only one of the identical twin members

• -> estimates from 42-84% heritability of stuttering 

• -> genes alone do not explain stuttering

Adoption studies

• study role of genetics & environment as adopted PWS little contact with biological relative during formative years 

• information from biological & adopted relatives of adopted PWS 

• => having biological parent with history of stuttering more important than being raised by parent with stuttering history

Summary of Genetic Perspectives

• Strong genetic component to developmental stuttering 

• No single gene or mutation that explains all cases of stuttering 

• Do not know yet what exactly is being transmitted – motor, linguistic, neurological, temperamental, … factors

Neurological perspectives

• Genes can lead to atypical development of brain structure & function? 

• Clear support for neurological perspective 

• brain damage & fluency problems 

• brain structure differences between PWS & FS 

• brain activation differences 

• other neurophysiological differences 

• reduced stuttering following Tx associated with changes in brain activity

Neurological perspectives - Cerebral Dominance theory

• Lee Edward Travis (1896-1987) 

• PWS have speech centers in both hemispheres instead of just the left 

• stuttering results from lack of cerebral dominance for speech production 

• 2 sides of brain ‘competing’ for control of speech muscles leads to breakdown in speech

• treatment: restore L-handedness

Aberrant sensory-motor integration for speech production

• reduced white matter integrity in left hemisphere SLF/AF 

• anomalous activity in M1 

• deactivation of left auditory cortex during speech 

• -> speech planning & integration with motor and sensory areas affected

Aberrant timing & sequencing of speech sounds

• Impaired structural connectivity in core areas supporting internal timing – SMA, putamen 

• Dysfunctional BG circuits may lead to increased influence of cerebellum

• ->  If pathways supporting internal timed movement are affected in stuttering, external pacing conditions may provide PWS with cues to bypass internal timing deficiencies

Compensatory/maladaptive role of right hemisphere homologues

• Larger regional volume/thickness & white matter integrity in right hemisphere 

• Contrasts sharply with left hemisphere findings 

• ->  Suggests that core deficit in stuttering is impairment of left hemisphere feedforward control system, which forces overreliance on right hemisphere feedback control mechanisms

Why are Neurological perspectives helpful?

• Support for differences in brain structure & function between PWS & FS 

• Studies focusing on children/lesions/treatment important 

• Group results!

Conclusions about the biological theories

• stuttering has genetic & neurophysiological bases 

• growing evidence for generally unstable/unreliable neuromotor system for speech

Multifactorial models

‘workers in the area of stuttering should adopt a multifactorial, non-linear and dynamic framework’

Multifactorial models search for causal factors of stuttering rather than precise cause 

potential causal factors 

• predisposing – makes susceptible 

• precipitating – hastens occurrence of disorder 

• Perpetuating

Multifactorial models

• Demand and Capacities Model 

• The Multifactorial Dynamic Pathways Theory

Demands-capacities model?

• Starkweather (1990) 

• Attempted speech performance exceeds capacities for fluent speech 

• No deficit implied (!) 

• Model accounts for stuttering at group level, but can also account for individual cases
  

• Stuttering due to failed balance between demands and capacities

If there’s lots of demands and they exceed the capacity there will be dysfluency

 The Multifactorial Dynamic Pathways Theory

• Smith & Weber (2017)  

• no core factor(s) necessary for stuttering to emerge or persist 

• stuttering is complex, resulting from interaction between various risk factors 

• variables may be internal or external & can interact in different ways in different children 

• small change in 1 factor may result in onset, development or persistence