[SLP10415] Theories of Stuttering Development

Theory

• An explanation of something or a phenomenon

• Does not apply to all

• Puts together findings in a systematic way so that past phenomena are explained and future ones are predicted

• Used by scientists to mean a formal set of hypotheses that explain the important causal relationships in a phenomenon

Hypothesis

• A specific and testable proposition derived from a theory

• A supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation

• ____ are tested, and the theory may be thrown out, improved, or partially confirmed as a result.

Historical perspective of Stuttering

• The clinician’s understanding about the possible etiologies of the problem will also have an influence on the clinician's treatment decisions.

• the clinician’s explanation may influence parent’s response to the child

  • How they deal with guilt 

  • How they respond when their child speaks fluently or stutters

Negative stereotypical responses

• A wide variety of groups including SLP clinicians, teachers, and naive listeners, have consistently assigned _____ __________ _______ to people who stutter

• Limited experience with individuals who stutter

• Influenced by books, movies, and the news media (neurotic or psychopathologic characteristics)

Greater mental effort

The ______ ______ _______ required by listeners to both recall and comprehend information from stuttered speech may elicit a negative behavioral response from listeners

Negative internal states

• Normally fluent speakers interpret stuttering in terms of the ________ _______ ______ (e.g., self-consciousness, anxiety, and stress) associated with their own speech disfluencies

• Fluent speakers infer from their own experiences of disrupted fluency that people who stutter (PWS) are chronically anxious or nervous.

Lack of Understanding about the nature of stuttering

Leads to failure to make a full adjustment in the case of the PWS, interpreting their experiences as similar to the reactions of the typical fluent speaker (too negative)

Theories of Etiology — A Historical Perspective

• Bloodstein and Bernstein Ratner

• Many unique aspects of developmental stuttering that differentiate stuttering from other communication problems

  • A relatively sudden onset between the ages of 2 and 4 (often following a period of fluent speech) 

  • The recovery of as many as 80% of children who stutter, especially females

• While some theories focus on the onset or etiology of stuttering, others attempt to explain the nature of the stuttering event.

Punishment for wrongdoing

Stuttering is a form of __________ ___ _________ or sin on the part of the child or the parent

Nitnit or njtnjt

• to talk hesitantly

• earliest recorded indication of stuttering provided by the Egyptians

• used a sequence of hieroglyphics to represent the term ____ or _______

“The Tale of the Shipwrecked Sailor”

Earliest known evidence of the human communication disorder

Abnormality in the tongue’s structure or function

• Many anatomical structures of the body, particularly those associated with speech production, have been implicated as a cause of stuttering.

• The belief that stuttering results from an _________ __ __ _______ ________ _ ____, or both, appears to have been the most widely held view between the time of Aristotle and the Renaissance, approximately 1500 C.E.

Various forms of surgery for PWS

• Severing hypoglossal nerve

• Piercing the tongue with hot needle

• Blistering tongue with fluids

• Encouraging smoking as sedative for the vocal folds

• Tonsil and adenoidectomy (early 1900s USA)

• Placing objects in the mouth or next to a variety of location in the vocal tract (both externally and internally) in order to elicit fluency

Repressed need hypothesis and psychosexual theory

Types of Psychological theories (2)

Psychological Theories

• Stuttering as a Symptom of Repressed Internal Conflict

• Suggesting that stuttering behaviors are a symptom indicative of an underlying psychological or emotional neurotic conflict 

• Stuttering is a psychopathology and that the overt stuttering behaviors are symptomatic of a deep-seated psychological disorder

Repressed Need Hypothesis

• Another term for neurotic or psychoanalytic explanation of stuttering

• Stuttering is seen as a neurosis and individuals who stutter do so as a result of a repressed, neurotic, unconscious conflict 

  • Stuttering behavior is seen as a symptom that is symbolic of this conflict

• A neo-Freudion view that the source of conflict was the result of inadequate interpersonal relationships 

• Stuttering is to gain attention sympathy or to void responsibilities 

Psychosexual Theory

• Fixation of psychological development at an oral or anal stage of infant sexual development 

• The one who stuttered had not experienced oral erotic gratification as an infant, possibly due to a disturbance in the mother-child relationship

• A person with stuttering tends to have a fixation 

• di pina breastfeed nung bata 

• possible due to disturbance in mother child relationship

Learning Theories

• Stuttering as a Learned Anticipatory Struggle

• Stuttering is a learned behavior

• At or near the onset of stuttering the speaker learns that speaking is difficult and subsequently learns to anticipate stuttering and struggles when attempting to produce fluent speech

Diagnosogenic theory, Anticipatory-struggle model, Continuity hypothesis, Classical Conditioning, Operant Conditioning

Types of Learning Theories (5)

Diagnosogenic Theories

• A most influential result of the Iowa development proposed by Wendell Johnson. 

• A belief that stuttering is caused by the misdiagnosis of typical dysfluencies as stuttering

• Stuttering evolves from normal fluency breaks to which the parents (or other significant people in the child’s environment) overreact and mislabel as “stuttering.” 

• The theory assumed that many children, including those who eventually stutter, experience a period of effortless fluency breaks.

• When children are penalized (typically by their parents) for producing these normal dis fluencies, the result is both greater anticipation and increased struggle behavior. 

• Stuttering, therefore, is created by the listener as normal breaks in fluency are shaped into stuttering.

Anticipatory-Struggle Model

• Also called “communicative failure and anticipatory struggle”

• Developed by Oliver Bloodstein

• Proposes that stuttering emerges from a child’s experiences of frustration and failure when trying to talk

• A view of stuttering that supposes the stuttering begins when a child experiences problems with communication (e.g. having many repetitions of being told he must try harder to say sounds correctly) and then develops a fear of having difficulty, which then causes tension and fragmentation of speech

Continuity Hypothesis

• Described by Bloodstein and Shames and Sherrick

• This view also proposes that stuttering develops from the normal fluency breaks produced by young children.

• Misdiagnosis and negative reactions by one or more listeners are not seen as part of the problem

• Both the tension and the fragmentation of fluency breaks increase as a result of communicative  pressure

• The development of stuttering is not a consequence of the child’s trying to avoid normal fluency breaks that have been mislabeled, but as tension and fragmentation increase, especially for part-word repetitions, the pattern becomes chronic and the child is more likely to be identified as someone who stutters.

Classical Conditioning

• Also called “respondent conditioning”

• The speaker learns to associate speaking with emotional arousal and the involvement of the autonomic nervous system (just as a dog salivates having learned that a ringing bell is associated with the dispensing of food).

  • Through a reinforcement schedule, a previously neutral stimulus (a bell) is associated with the food

Stage 1 of Classical Conditioning

The speech features of stuttering are a “form of fluency failure” which is believed to be associated with a negative emotional state (negative emotion causes initial fluency failure)

Stage 2 of Classical Conditioning

Negative emotion and resulting fluency failure become linked to certain external stimuli through associative learning

Stage 3 of Classical Conditioning

There is an extension of the range of stimuli to which the negative emotional response becomes associated.

Operant Conditioning

• Also called "instrumental conditioning"

• Based on B.F. Skinner’s concepts of experimental analysis of behavior 

• The primary association in operant models is between a behavior and the consequence of the behavior. 

• Propose that the fluency breaks of young children are shaped by the response they elicit

• Speaker responses to listener reactions tend to shape somewhat distinctive coping behaviors

Positive reinforcement, negative reinforcement, positive punishment, and negative punishment

Kinds of operant conditioning (4)

Positive reinforcement

Adding something they like to increase or decrease the behavior

Negative reinforcement

Removing something they don’t like to increase or decrease the behavior

Positive punishment

Adding something they don’t like to increase or decrease the behavior

Negative punishment

Removing something they like to increase or decrease the behavior

Physiological Theories

• The speaker's ability to produce fluent speech breaks down, particularly in response to various forms of stress.

  • Cerebral Asymmetry

  • Temporal Processing

  • Linguistic Processing

  • Cybernetic Dysfunction

  • Genetic Factors

  • Modified Vocalization

• Problems with the speaker’s anatomical and physiological systems

Left handed or ambidextrous

A number of anecdotal reports suggested that individuals who stutter are more likely to be ____ ______ _ ________ than nonstutterers and that the onset of stuttering had occurred in conjunction with attempts to change their handedness in some way.

Cerebral Dominance Theory

• Samuel T. Orton (1927)

• Orton and Travis theorized that because the muscles of the speech mechanism receive nerve impulses from both the left and right hemispheres of the brain, it is necessary for one hemisphere to be dominant over the other in order for speech movements to be properly synchronized and proposed that the left hemisphere was the more dominant in this process. 

• They suggested that the nervous system of PWS had not matured sufficiently to achieve left hemispheric dominance over speech movements, and that this maturational failure resulted from hereditary influences, disease, injury, or even emotional arousal and fatigue.

  • For PWS: Right side of the brain is more dominant. 

Hemispheric Dominance

• The phenomenon that one hemisphere of the brain (left or right) takes the lead or is stronger for a particular function.

• Refers to the fact that the left side of the brain is usually more specialized for speech and language than the right side. 

Modified Vocalization Hypothesis

• Popular during the late 1960s and 1970s

• Attribute an inefficiency or over adduction of the vocal folds as a core aspect of stuttering etiology. 

• Proposed by Wingate (1969)

• Led to many investigations of vocal fold function during both stuttered and fluent speech.

• Although not specifically implicating vocal folds, Starkweather (1995) stated that “elevated muscle activity is itself the proximal cause of stuttering behavior”

• This may be questionable, as Marilyn Monroe herself presented with a breathy voice and still exhibited stuttering.

Dual Premotor Systems Hypothesis

• Alm (2004, 2005) expands on the roles of the basal ganglia in stuttering by emphasizing their motor functions.

Direct medial pathway and Lateral Indirect medial pathway

2 Associated Pathways important to the Dual Premotor Systems Model/Hypothesis

Basal Ganglia

• Subcortical structures in the center of the brain that receive input from many areas of the cerebral cortex and the limbic system.

• Plays a key role in the automatization of fast motor sequences and provide timing cues to the supplementary motor area (SMA), which in turn plays a key role in motor control and timing for many activities, including speech.

Frontal Cortex

Normally, the medial and lateral pathways work in synergy to modulate the activity of the _____ _____.

High number of D2 receptors

Results in reduced inhibition of the cortex. A peak in dopamine receptors in the basal ganglia occurs at age 2.5 to 3 years, approximately the same time of stuttering onset in young speakers.

Lower D1/D2 ratio in boys

A decreased function of the direct (D1/D2) pathway results in deficient activation of the desired action, such as initiating speech movements. Impairment of the direct pathway prohibits diffuse inhibition of the cortex, resulting in unintended movements and the impaired release of intended movement.

Medial System

• Includes the basal ganglia

• Associated with self-initiated actions, and in connection with the limbic system, motivational factors

• Alm associates the medial system with the production of spontaneous speech (similar to the emotionally based response of a true smile)

Lateral System

• Including the lateral premotor cortex and the cerebellum

• Functions in response to sensory input based on feedback control and is associated with voluntary and conscious control.

• Associated with speech that is mediated by external stimuli (similar to non-emotional or “staged” smile)

Covert Repair Hypothesis

• Proposes a psycholinguistic perspective involving both production and perception to account for fluency breaks. 

• An explanation of stuttering as the result fo the brain’s stopping production of speech when it detects an error in the plan that the brain has made to produce a word. 

  • Covert repair: when the brain detects there is something wrong, the brain repairs.

• The model proposes that internal or covert monitoring allows speakers to detect errors in phonological encoding prior to the implementation of articulatory commands.

• As errors are detected, the planning of the phonetic sequence is interrupted and the correct plan is initiated.

• As a result of this error detection and subsequent covert repair of the speech plan, fluency breaks occur.

Covert repair

when the brain detects there is something wrong, the brain repairs

Execution and Planning Model (EXPLAN)

• Howl & Au-Yeung (2002)

• Elaborates the covert repair hypothesis by suggesting independent linguistic and motor processes

• Presented as an autonomous model in that this sequence of production is not linked to internal or external monitoring.

• Speech is initiated by an internal cognitive-linguistic system that covertly plans (PLAN) the syntactic, lexical, phonetic features in serial order.

• The motor process organizes and executes (EX) the output.

• Linguistic is planning, motor is execution

• Fluent speech occurs when the motor system receives and executes the linguistic sequences in order. If the linguistic system experiences difficulty in generating a linguistic (syntactic, lexical, and phonetic) sequence, the motor system is unable to execute fluent speech.

• Breakdowns in fluency occur at the language-speech interface; although one linguistic plan is completed the next plan is not ready for execution.

• Speakers may respond by stalling and either repeating speech already produced (whole words) or pausing, allowing time for the completion of the linguistic plan. Speakers may also continue with the linguistic sequence that is available and attempt to advance forward. However without sufficient time speakers are likely to:

  • prolong the fit part of the word (e.g., ssssister) 

  • repeat the first syllable (as in suh-suh-sister) 

  • insert a pause (as in s-ister)

Cybernetic and Feedback Models

• Fairbanks (1954) and Mysak (1960) 

• Cybernetic theory has to do with the automatic control inherent in many mechanical and biological systems.

  • Our body have feedback systems and once we receive that feedback nagkakaroon ng errors 

• Incorporate various forms of feedback that are used to regulate the output of a system–similar, for example, to a thermostat that is part of a closed-loop arrangement that controls the temperature of a building. The goal of such a system, termed servosystem, is to match the intended output to the actual output and reduce any differences that are detected between the two–the error signal–to zero.

• If for some reason there is a distortion of the information arriving via the feedback loop, the error signal will be incorrect. When this occurs, the system tends to go into oscillation. 

• The basic idea was that for speakers who stutter, the distorted feedback creates the misconception that an error has occurred in the flow of speech. Stuttering occurs when the speaker attempts to correct an error that has, in fact, not occurred.

Multifactorial Theories

Stuttering as a Multifactorial Dynamic Disorder

Dynamic Multifactorial model, Demands and Capacities model, Neurophysiological model

Theories under Multifactorial theories (3)

Dynamic Multifactorial Model

• Stuttering may be seen as multifactorial because many factors (e.g. genetic, emotional, cognitive, social, environmental) interact to create it. 

• It is also dynamic because the overt signs of stuttering are seen as surface manifestations of an ever changing neurophysiological process underlying the disorder.

Demands and Capacities Model

• A view of stuttering that suggests that stuttering results when the demands put on a child’s speech are greater than the child’s capacity for fluency

• proposes that children who stutter possess genetically influenced tendencies for fluency breakdown that interact with environmental factors to both originate and maintain the problem

• the fact that human genotypes (the fundamental hereditary constitution of an individual) interact with the environment to create what we observe as the phenotype (the outward, visible expression of a specific person) 

• nature-nurture

Demands

Environmental and Self-imposed demands

Environmental (extenral) demands

• Fast-speaking rates 

• Time pressure 

• Competition and lack of turn taking of other speakers

• pressure to talk rapidly

Self-imposed (Internal) demands

• Overstimulation of language centers and demand for language performance 

• Need to formulate complex sentences 

• Excitement and anxiety 

• Cognitive requirements to express complicated thoughts

Capacities

• inherited tendencies, strengths, weaknesses, and perceptions which may influence child’s fluency

  • Motoric (initiate and control, smooth coarticulation)

  • Linguistic (formulate sentences)

  • Socio-emotional (under communicative/emotional stress)

  • Cognitive (metalinguistic skills) 

• capacity to manage the complex components of spoken language production at a high rate

Neurophysiological Model

• De Nil and his colleagues describe a model that provides a comprehensive and unifying model of stuttering

• also includes capacities or skills similar to those noted in the demands and capacities model

• proposes that just as nature and nurture are not separate phenomena, psychological and neurophysiological processes are not independent entities 

Processing, output, and contextual influences

Dynamic interplay among three levels of influence on human behavior and on stuttering in particular (Neuropsychological model)

Central Neurophysiological Processes

Processing influence

Motor, cognitive, language, social, and emotional processes

Output influence

Contextual

Environmental influence