The Iowa Therapies: Secondary Behaviors and Acceptance
Modern stuttering treatment began in 1927 with the formation of the University of Iowa Speech Clinic. Lee Edward Travis, Bryng Bryngelson, Wendell Johnson, and Charles Van Riper developed what are now referred to as “the Iowa therapies,” including indirect therapy for children and stuttering modification therapy for adults.
Indirect therapy for childhood stuttering aims to reduce a child’s fears and anxieties about stuttering by altering the parents’ behavior. It’s based on a theory that stuttering begins “not in the child’s mouth but in the parent’s ear.”  Parents are instructed to not react to the child’s stuttering, but instead to speak slowly to their child, to pause before answering the child’s questions, to reduce the number of questions they asked of the child, and to slow the pace of family life.
Stuttering modification therapy for older children and adults is focused on accepting stuttering, reducing stutterers’ speech-related fears and anxieties, and helping stutterers to communicate better despite stuttering. Because they couldn’t treat the core behaviors of stuttering, speech-language pathologists of this era managed the secondary symptoms associated with stuttering to improve stutterers’ ability to communicate, while accepting stuttering.
Indirect therapy has been proven ineffective for helping children. Efficacy studies have found that stuttering modification therapy has little or no long-term effect on stuttering.
Fluency Shaping: Treating Core Stuttering
The second era of stuttering treatment began in 1965 when Israel Goldiamond discovered that delayed auditory feedback (DAF) induces stutterers to speak slowly and fluently. This discovery led to the development in the 1970s of fluency shaping, which has been proven efective in many studies with adults and school-age children. 
Fluency shaping treats the core behaviors of stuttering, training even severe stutterers to talk fluently. Fluency shaping programs typically ignore secondary stuttering behaviors, including speech-related fears and anxieties, assuming that these will disappear if the stutterer learns to speak fluently.
Fluency shaping therapy trains conscious awareness and control of speech processes that are normally automatic. Too often the result is that a stutterer can think about how he is speaking, and speak fluently; or think about what he is saying and revert back to stuttering (a dual-tasking problem). Fluency shaping therapy has a reputation for producing fluency in low-stress conversations in speech clinics, but failing to transfer to high-stress situations outside the speech clinic.
Neurological Treatments: Getting at the Roots of Stuttering
The neurological era of stuttering treatment began in the 1990s with brain imaging studies of adult stutterers. These studies found neurological abnormalities during stuttering. Some of these abnormalities, such as underactive auditory processing, were unexpected.
In 1993, Joseph Kalinowski, Andrew Stuart, Michael Rastatter and colleagues published a seminal study finding that DAF and a newer technology called frequency-altered auditory feedback (FAF) reduced stuttering at normal and faster-than-normal speaking rates, without conscious effort or control. This challenged the belief of the fluency shaping era that slowing down was the key to fluent speech. The research instead suggested that altered auditory feedback (AAF) corrects a neurological abnormality, likely the auditory processing abnormality found in the brain imaging studies.
In 1996 David E. Comings and colleagues correlated stuttering to three genes related to the neuroransmitter dopamine.
Medications have been tried with stutterers beginning with tranquilizers in the 1950s and the dopamine antagonist haloperidol in the 1960s , with severe side effects and minimal improvement in speech. Beginning in 1999 Gerald Maguire and colleagues published studies  finding that the newer dopamine antagonist medications risperidone and olanzapine reduced stuttering with fewer side effects.
In 2005 Ehud Yairi and Nicoline Ambrose published the results of longitudinal studies examining young children soon after the onset of stuttering, and following the development of the disorder for five years or more. The results dispelled many myths and suggested that stuttering begins when the speech and language areas of a child’s brain develop at different rates.
The aim of neurological treatments is to reduce stuttering without conscious effort, control, or training. Neurological treatments ignore both core stuttering behaviors and secondary behaviors, including speech-related fears and anxieties, in the belief that correcting the neurological abnormalities leads to fluent speech and the disappearance of secondary behaviors.
As an example of
neurological era thinking, Joseph Kalinowski and Tim Saltuklaroglu wrote the following letter in 2007:
For the last 40 years, practitioners of stuttering therapy have advocated systematic retraining of the peripheral speech mechanism in an attempt to create speech movements believed to be incompatible with stuttering. Such re-training has often resulted in “pseudofluent” or “labored” speech, characterized by unnaturalness, droning, and conspicuousness. Further, these new speech patterns have shown a strong history of instability and propensity for relapse, despite the countless hours taken to establish them…
…the major corpus of current evidence suggests, and most “experts” now concur, that stuttering is an involuntary central neurological disorder. Therefore, logically speaking, attempting to combat the disorder by altering speech patterns without attacking the source of the pathology seems only to provide temporary relief from the overt symptoms of stuttering. As such, these methods appear to be largely inefficient in treating the disorder, a contention that is obvious to most and most notably to the person who stutters.
Our research group suggests that stuttering can be inhibited at a central level, closer to its source, [with the result that] disruptions of stuttering are usually totally absent [by using] delayed auditory feedback (DAF) and frequency altered feedback (FAF)…
Prosthetic devices (e.g., all-in-the-ear fluency aids) that emulate choral speech (by using DAF and FAF) seem promising, and pharmacological agents for general inhibition also show potential…The data is irrefutable—current stuttering therapies have fallen short of their promises, and stuttering inhibition should be further explored. 
Neurological era treatments tend to be more promise than proven. Too often the neurological processes of stuttering are barely glimpsed or poorly understood. The early childhood research has not yet led to a new, more effective treatment for early childhood stuttering. Genetic research is controversial. Anti-stuttering medications are not highly effective and have side effects. Electronic devices are too often years ahead, in technology or marketing claims, of efficacy research.
Each era of stuttering treatment has contributed to the field. Each has shortcomings and each treatment alone is insufficient. Successful treatment of adult stuttering requires combining ideas from all three eras.
 Bloodstein, O. & Bernstein Ratner, N., A Handbook on Stuttering (2007; ISBN 978-1-4180-4203-5), pages 58-59.
 Bothe, A., Davidow, J., Bramlett, R., & Ingham, R. Stuttering Treatment Research 1970–2005: I. Systematic Review Incorporating Trial Quality As-sessment of Behavioral, Cognitive, and Related Approaches. American Journal of Speech-Language Pathology, 15, 321–341, November 2006.
 Bloodstein, O. & Bernstein Ratner, N., A Handbook on Stuttering (2007; ISBN 978-1-4180-4203-5), page 376.
 Bloodstein, O. & Bernstein Ratner, N., A Handbook on Stuttering (2007; ISBN 978-1-4180-4203-5), page 377.
 Kalinowski, J. & Saltuklaroglu, T. The Inhibition of Stuttering: A Viable Alternative to Contemporary Therapy. Family Medicine, 35, (1), 7-8.