This study aims to test whether the addition of transcranial direct current stimulation (TDCS) to speech fluency training results in improvements in speech fluency in adults with developmental stuttering. Half of the participants will receive anodal TDCS on five consecutive days, the other half will receive a sham stimulation for the same amount of time.

Studies using TDCS have shown improvements in motor performance, and in expressive language skills in clinical and healthy populations. The benefits of single sessions of TDCS are short-lived. However, stimulation over multiple sessions can increase and prolong learning effects that can persist for several weeks after the end of the stimulation period. We aim to target left hemisphere frontal regions involved in speech production with TDCS, and to pair this stimulation with speech fluency training.

Inclusion Criteria:

• Native speaker of English.
• Right handed.
• Participant has moderate to severe Developmental Stuttering (Stammering)

Exclusion Criteria:

• Speech, language or communication disorder other than Developmental Stuttering.
• Sensory impairment (hearing loss or visual impairment)
• History of drug abuse.
• History of seizures
• History of a neurological or psychiatric illness.
• History of neurosurgical procedure.
• Currently taking certain prescription medications such as anti-depressants and anti-malarial medication (as these may lower the seizure threshold)