In case of a tic, these components are intended to increase tic awareness, develop a competing response to the tic, and build treatment motivation and compliance. HRT is based on the presence of a premonitory urge, or sensation occurring before a tic. HRT involves replacing a tic with a competing response—a more comfortable or acceptable movement or sound—when a patient feels a premonitory urge building.Controlled trials have demonstrated that HRT is an acceptable, tolerable, effective and durable treatment for tics; HRT reduces the severity of vocal tics, and results in enduring improvement of tics when compared with supportive therapy. HRT has been shown to be more effective than supportive therapy and, in some studies, medication. HRT is not yet proven or widely accepted, but large-scale trials are ongoing and should provide better information about its efficacy in treating Tourette syndrome. Studies through 2006 are "characterized by a number of design limitations, including relatively small sample sizes, limited characterization of study participants, limited data on children and adolescents, lack of attention to the assessment of treatment integrity and adherence, and limited attention to the identification of potential clinical and neurocognitive mechanisms and predictors of treatment response".  Additional controlled studies of HRT are needed to address whether HRT, medication, or a combination of both is most effective, but in the interim, "HRT either alone or in combination with medication should be considered as a viable treatment" for tic disorders.