**My summary**: (of the post) * Stuttering does not occur on every syllable, so there must be a trigger for each moment of stuttering. * These triggers consist of certain inherent features of spoken language. They are more likely to trigger stuttering because they are associated with increased motor demands. These increased demands disrupt speech motor execution. * Stuttering is associated with linguistic features * Language is not necessarily impaired in people who stutter but rather there are inherent features of language that, when realized in speech, trigger stuttering * ​ **Triggers**: (that are associated with increased motor demands) * inherent features of spoken language * high expectation: reduction in motoric task demands * variable syllabic stress (high expectations: (1) reduction in the variability in contrastive syllabic stress" e.g., due to prolongation, syllable-timed or rhythmic speech; (2) reduction in the variability in emphasis from syllable to syllable) * linguistic complexity (high expectation: reduction in linguistically complex utterances) * excitement or anticipation or fear or performance anxiety * communicative context * paying more attention to fluency or increasing their control over their stuttering * ​ ​ ​ * ​ **Modulating factors** * The triggering mechanism is modulated by intrinsic factors. * Intrinsic factors: * Physiological arousal (which refers to the readiness of the body to react to stressful internal and external stimuli): Physiological arousal increases the threshold when stuttering triggers. * . This is another empirical question raised by this model. The availability of cognitive resources during communication has also been shown to have an effect on stuttering (see Metten et al., 2011). Metten et al. (2011) found that stuttering increased when a competing linguistic task diverted cognitive resources away from speaking. Interestingly, dual tasking also interfered with speech production for the normally fluent participants in the control group, who had many more normal disfluencies in this condition. According to the P&A model, then, dual- or multi-tasking where the tasks share resources can lower the threshold at which stuttering is triggered. Interestingly, it is also the case that stuttering may reduce during dual tasking where the secondary task does not share cognitive resources (Arends et al., 1988, Vasic and Winjen, 2005). In this model, the modulating factors are considered to be unique for each individual. For example, in a study of 140 adults seeking treatment for their stuttering, Iverach et al. (2011) found wide variation in scores on the Unhelpful Thoughts and Beliefs About Stuttering scale and on a range of psychological tests. Modulating factors will likely be influenced by, among other things, individual experiences (for example, teasing during childhood), anxiety, fear of negative evaluation and stuttering severity, all in turn possibly influenced by individual differences in emotional reactivity (Walden et al., 2012) and resilience (Craig, Blumgart, & Tran, 2011). Environmental stressors are seen as important in the P&A model, just as they are in the Demands and Capacities model. However, in the P&A model the individual's perceptions of, and/or reactions to, potential environmental stressors are also important in determining the threshold at which stuttering is triggered. For example, one person who stutters may be highly anxious when talking in a group, whereas another may not. Modulating factors, then, can be seen as the major contributor to the variability of stuttering within individuals, across communicative contexts. To summarize the P&A model, an underlying deficit in neural processing is the necessary condition for stuttering to occur, while features of spoken language trigger moments of stuttering. Together, these form the necessary and sufficient conditions for a moment of stuttering to occur. In the model, differences in stuttering severity across individuals can be attributed to differences in the extent of the neural processing deficit across individuals, while variability of stuttering within individuals, across communication contexts, can be attributed to the range and potency of modulating factors in individuals."