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Many studies have examined the effects of TS on neuropsychological variables. Some of these variables seem directly related to tic generation (i.e., difficulties with motor inhibition) but many studies have revealed wide-ranging effects. However, given the high rates of comorbidities, researchers are generally trying to perform studies with sufficient power to separate effects associated with TS itself and those related to TS-comorbidities.   Two studies examined the effects of comorbidities. Social responsiveness and cognitive flexibility were examined in TS children and adolescents \citep{25631951}. TS subjects were rated as having poorer social motivation and skills, using the Social Responsiveness Scale, compared to age-matched controls. TS subjects also took significantly longer to complete the Trail Making Tests which measure cognitive flexibility and visual motor integration. However, of the 31 TS subjects, 11 had OCD, 18 had ADHD and 8 had an anxiety disorder. Once these comorbidities were taken into account, group differences on the Trail Making Tests and the Social Responsiveness Scale were no longer significant. These findings demonstrate the need for studies to have adequate sample sizes to provide sufficient power to disentangle effects due to TS directly and those related to comorbid conditions. Another study included was designed to separate effects due to OCD and TS \citep{25296570}. Sustained attention, using a continuous performance test, was examined in 48 children and adolescents who had OCD alone, tic disorders (TD) alone or both OCD and TD. A high rate of ADHD was seen in all  groups that (62% of the OCD+TD group, 27% in the TD alone group, and 20% in the OCD alone group). Anxiety was also frequent (77% in the OCD+TD group compared to 49% for the other two groups combined). The OCD+TD group  had more errors of omission and higher reaction time variability. These results of this study provide additional evidence that the OCD+TD phenotype is associated with more severe symptoms including attentional difficulties and symptoms of anxiety.  It is well established that many factors affect tic frequency. Two recent studies examined the effects of attention on tic frequency and the results have implications for how treatment protocols could be modified to increase effectiveness. The role of attention on tic frequency was examined under several conditions \citep{25185800}. In the first study mean tic frequencies were significantly higher for 12 TS subjects compared to baselines when they were alone in a room. Then they were recorded while looking at themselves in a mirror. A second study was performed to determine whether the increase in frequency was due to increased attention to the tics themselves or due to increased self-awareness in general. In addition to the conditions from the first study, the 16 subjects were also shown videos of themselves while they were not ticcing. Tic frequency was again lower during the baseline compared to the mirror condition. Tic frequency was lower when subjects were watching the video of themselves while not ticcing. The authors suggest that future treatments stress attention to states when patients experience fewer tics. Another study of TS adults \citep{25486384} compared tic frequency while subjects were engaged in tasks that involved attending to particular fingers, colored circles, or whether a tic had occurred during a specific 2-second interval during tic suppression or free ticcing conditions. Not surprisingly, more tics were seen during a baseline free ticcing condition. During the attention tasks, tic frequency was greatest while they focused on their tics, decreased on the color attention condition, and decreased further on the finger attention condition. When subjects suppressed their tics, they reduced their baseline tic frequency similarly across all attention conditions. The results are consistent with the idea that internally-directed attention, especially with focus on tics, may contribute to momentary tic severity. The report's authors also suggested that behavioral treatment might be more effective if it focused on teaching patients to focus on external events and voluntary actions when they are in situations that are most likely to result in ticcing.   The stereotyped nature of tics has led some to suggest that the neural systems involved in habitual behavior may also be associated with tic generation. A complex, three-stage instrumental learning paradigm was used to compare antipsychotic-medicated and unmedicated TS adults without ADHD with a control group to determine whether they differed in goal-directed _vs._ habitual behavior \citep{26490329}. First subjects learned to associate six different stimuli with six specific outcome pictures and a specific response (i.e., left or right key press). During the second stage, subjects were presented with two outcomes with an indication that one outcome was devalued so that it was no longer associated with point rewards and subjects had to press the key associated with the outcome that would still generate points. During the third stage (_i.e._, "slip-of-action" stage), the six outcomes were presented simultaneously with indications that two were devalued so that responding to the associated stimuli would no longer be rewarded with points. Subjects were instructed to press the key associated with stimuli associated with the still valued outcomes and withhold the response (Go/No-Go) for stimuli associated with devalued outcomes. This task determined whether excessive "slips of action" were related to a working memory deficit or deficient response inhibition rather than outcome devaluation insensitivity. There were no group performance differences for the first two stages of the instrumental learning task or on the baseline Go/No-Go task. However, unmedicated patients showed a significantly higher response rate to devalued outcomes compared to controls (in Bonferroni-corrected _post hoc_ analyses), while there was no difference between medicated subjects and controls. In addition, in unmedicated subjects tic severity was correlated with response rates to devalued outcomes and was also correlated with stronger structural connectivity between the right supplementary motor cortex and the posterior putamen. The results obtained in this study contrasted with results on similar tasks obtained with subjects with obsessive-compulsive disorder without tics. The authors argued that over-reliance on habits in OCD without tics is associated with impaired knowledge of response-outcome associations, while this type of learning was intact in both TS groups in this study. They also concluded that habit formation is enhanced in unmedicated TS subjects but may be corrected with medication.   Sustained attention, using a continuous performance test, was examined in 48 children who had OCD alone, tic disorders (TD) alone or both OCD and TD \citep{25296570}. A high rate of ADHD was seen in all groups (62% of the OCD+TD group, 27% in the TD alone group, and 20% in the OCD alone group). Anxiety was also frequent (77% in the OCD+TD group compared to 49% for the other two groups combined). The OCD+TD group had more errors of omission and performed more poorly on other measures of sustained attention compared to the other two groups. Although an attempt was made to examine the specific effect of ADHD in the OCD+TD group, the subgroups were quite small (8 in the OCD+TD+ADHD, 5 in the OCD+TD-ADHD), thereby limiting the power to detect additional differences. However, reaction time variability, which is commonly increased in ADHD, was higher in the OCD+TD group than for the groups with OCD alone or TD alone. This study exemplifies the challenges of trying to separate out the effects of comorbidities in children with TS.  Anecdotal evidence has suggested that tics decrease when people are involved in musical activity, so \citet{Bodeck_2015} systematically studied the effects of music. Questionnaires completed by 29 patients supported the idea that listening to music and performing music decrease tic frequency. In a second study, tics almost completely stopped when subjects were performing music. Listening to music and mental imagery of musical performance also resulted in a decrease in tic frequency. The authors suggested that focused attention, along with fine motor control and goal-directed behavior, produced the decrease in tics.  In an intriguing report from a group studying social cognition in TS, people with TS and controls demonstrated intact mentalizing when observing animated triangles demonstrating simple and complex interactions \citep*{26177119}. However, people with TS also tended to attribute human-like intentions when the two triangles were moving randomly. This tendency was not explained by clinical symptoms or by other constructs such as executive function or alexithymia.