**Summary**: (of the stutter hypotheses) *EXPLAN Hypothesis:* * Stuttering arises from a timing mismatch between speech planning (PLAN) and execution (EX) processes in speech production. This mismatch leads to disfluencies as the speech plan fails to achieve sufficient completeness for timely execution. **Speech Planning (PLAN):** This involves the cognitive processes required to formulate what and how to say a planned word or sound (like, selecting words, structuring sentences, and preparing the linguistic content, and phonological encoding). **Speech Execution (EX):** This involves the physical act of speaking (motor movements of articulators to produce sounds) * **Mechanism of stuttering:** Occur when the speech plan is incomplete or insufficiently prepared at the time it is required for execution. This results in stalling behaviors (repetitions, prolongations) as the speaker attempts to buy time for planning to catch up *Anticipatory Struggle Hypothesis:* * Stuttering is a result of the anticipation of speech or communication failure, leading to maladaptive speech adjustments and disfluencies. In an attempt to avoid failure, PWS make conscious or unconscious changes to their speech production, which paradoxically result in stuttering - similar to Johnson's perspective (effort to avoid stuttering actually triggers it), and Sheehan's perspective (the desire to speak (approach) conflicts with the fear of stuttering (avoidance) resulting in disfluencies) * **Factors Influencing Stuttering:** Immediate factors (like delayed language development or articulation problems) and general communicative pressure (like high parental expectations, societal pressures, or the speaker’s own high standards). Stuttering is cognitively mediated by the belief in anticipated speech failure, which can be self-sustaining once established. The cues that evoke stuttering vary between individuals based on personal experiences and perceptions *VRT Hypothesis:* * Stuttering results from an excessively high activation threshold required for the release of speech plans. A certain level of activation is needed before a speech plan can be executed. In people who stutter, unrealistic expectations about speech accuracy can lead to evaluating 'the anticipation of communication failure' negatively resulting in raising the execution threshold too high - leading to increased anxiety and adjustments (such as, the desire to speak our own name too accurately or appropriately). So, this mechanism acts as a quality control to prevent the execution of incorrect or inappropriate speech plans - that decides whether we say our thoughts out loud. This release threshold is variable and fluctuates from word to word based on the speaker's perception of the importance and accuracy required for their speech * **Role of dopamine**: The desire to speak increases post-synaptic dopamine levels, while the fear of communication failure or facing negative reactions decreases these dopamine levels. During the critical period of speech development, children's release thresholds are still being fine-tuned. Negative social feedback can condition them to raise their thresholds excessively, contributing to persistent stuttering. Speech blocks are more likely to result from Operant Conditioning (than from classical conditioning) - resulting in poorly fine-tuning the execution threshold. Classical conditioning is likely responsible for the gradual generalisation of stimuli that can elicit blocks as the stutter develops. Dopamine plays a crucial role in operant conditioning, that occurs when a person’s speech performance is evaluated by the speaker as “punishing” or “rewarding". In contrast, classical conditioning occurs simply when two stimuli occur at the same time – and thus become associated with one another