Many aspects of human behavior are inherently rhythmic, requiring production of rhythmic motor actions as well as synchronizing to rhythms in the environment. It is wellestablished that individuals with ADHD exhibit deficits in temporal estimation and timing functions, which may impact their ability to accurately produce and interact with rhythmic stimuli. In the current study we seek to understand the specific aspects of rhythmic behavior that are implicated in ADHD. We specifically ask whether they are attributed to imprecision in the internal generation of rhythms or to reduced acuity in rhythm perception. We also test key predictions of the Preferred Period Hypothesis, which suggests that both perceptual and motor rhythmic behaviors are biased towards a specific personal 'default' tempo. To this end, we tested several aspects of rhythmic behavior and the correspondence between them, including spontaneous motor tempo (SMT), preferred auditory perceptual tempo (PPT) and synchronization-continuations tapping in a broad range of rhythms, from sub-second to supra-second intervals. Moreover, we evaluate the intra-subject consistency of rhythmic preferences, as a means for testing the reality and reliability of personal 'default-rhythms'.We used a modified operational definition for assessing SMT and PPT, instructing participants to tap or calibrate the rhythms most comfortable for them to count along with, to avoid subjective interpretations of the task.Our results shed new light on the specific aspect of rhythmic deficits implicated in ADHD adults. We find that individuals with ADHD are primarily challenged in producing and maintaining isochronous self-generated motor rhythms, during both spontaneous and memory-paced tapping. However, they nonetheless exhibit good flexibility for synchronizing to a broad range of external rhythms, suggesting that auditory-motor entrainment for simple rhythms is preserved in ADHD, and that the presence of an external pacer allows overcoming their inherent difficulty in self-generating isochronous motor rhythms. In addition, both groups showed optimal memory-paced tapping for rhythms near their 'counting-based' SMT and PPT, which were slightly faster in the ADHD group. This is in line with the predictions of the Preferred Period Hypothesis, indicating that at least for this well-defined rhythmic behavior (i.e., counting), individuals tend to prefer similar time-scales in both motor production and perceptual evaluation.

Several studies have found that the motor rhythms that individuals produce spontaneously, for example during finger tapping, clapping or walking, are also rated perceptually as ‘very comfortable’ to listen to. This motivated proposal of the Preferred Period Hypothesis , suggesting that individuals have a characteristic preferred rhythm, that generalizes across perception and production. However, some of the experimental procedures used previously raise two methodological concerns: First , in many of these studies, the rhythms used for assessment of participants’ Perceptual Preferred Tempo (PPT) were tailored specifically around each participant's personal Spontaneous Motor Tempo (SMT). This may have biased results toward the central rhythm used, artificially increasing the similarity between spontaneous motor and auditory perceptual preferences. Second , a key prediction of the Preferred Period Hypothesis is that the same default rhythms are repeatedly found within-subject. However, measures of consistency are seldom reported, and increased within-subject variability has sometimes been used to exclude participants. The current study was an attempt to replicate reports of a correspondence between motor and perceptual rhythms, and closely followed previous experimental protocols by conducting three tasks: SMT was evaluated by instructing participants to tap ‘at their most comfortable rate’; PPT was assessed by asking participants to rate a 10 different rhythms according to how ‘comfortable’ they were; and motor-replication of rhythms was assessed using a Synchronization-Continuation task, over a wide range of rhythms. However, in contrast to previous studies, for all participants we use the same 10 perceptual rhythms in both the PPT and Synchronization-Continuation task, irrespective of their SMT. Moreover, we assessed and report measures of within- and between-trial consistency, in order to evaluate whether participants gave similar rating and produced similar motor rhythms across multiple sessions throughout the experiment. The data presented here fail to show any correlation between motor and perceptual preferences, nor do they support improved synchronization-continuation performance near an individual's so-called SMT or PPT. Rather, they demonstrate substantial within-subject variability in the spontaneous motor rhythms produced across repeated sessions, as well as their subjective rating of perceived rhythms. This report accompanies our article “Spontaneous and Stimulus-Driven Rhythmic Behaviors in ADHD Adults and Controls” [1] , and provided motivation and insight for modifying the procedures used for SMT and PPT evaluation, and their interpretation.

Purpose: Humans have a near-automatic tendency to entrain their motor actions to rhythms in the environment. Entrainment has been hypothesized to play an important role in processing naturalistic stimuli, such as speech and music, which have intrinsically rhythmic properties. Here, we studied two facets of entraining one's rhythmic motor actions to an external stimulus: (a) synchronized finger tapping to auditory rhythmic stimuli and (b) memory-paced reproduction of a previously heard rhythm. Method: Using modifications of the Synchronization–Continuation tapping paradigm, we studied how these two rhythmic behaviors were affected by different stimulus and task features. We tested synchronization and memory-paced tapping for a broad range of rates, from stimulus onset asynchrony of subsecond to suprasecond, both for strictly isochronous tone sequences and for rhythmic speech stimuli (counting from 1 to 10), which are more ecological yet less isochronous. We also asked what role motor engagement plays in forming a stable internal representation for rhythms and guiding memory-paced tapping. Results and Conclusions: Our results show that individuals can flexibly synchronize their motor actions to a very broad range of rhythms. However, this flexibility does not extend to memory-paced tapping, which is accurate only in a narrower range of rates, around ~1.5 Hz. This pattern suggests that intrinsic rhythmic defaults in the auditory and/or motor system influence the internal representation of rhythms, in the absence of an external pacemaker. Interestingly, memory-paced tapping for speech rhythms and simple tone sequences shared similar “optimal rates,” although with reduced accuracy, suggesting that internal constraints on rhythmic entrainment generalize to more ecological stimuli. Last, we found that actively synchronizing to tones versus passively listening to them led to more accurate memory-paced tapping performance, which emphasizes the importance of action–perception interactions in forming stable entrainment to external rhythms.

1 2 Many aspects of human behavior are inherently rhythmic, requiring production of rhythmic 3 motor actions as well as synchronizing to rhythms in the environment. It is well-established 4 that individuals with ADHD exhibit deficits in temporal estimation and timing functions, which 5 may impact their ability to accurately produce and interact with rhythmic stimuli. In the current 6 study we seek to understand the specific aspects of rhythmic behavior that are implicated in 7 ADHD. We specifically ask whether they are attributed to imprecision in the internal 8 generation of rhythms or to reduced acuity in rhythm perception. We also test key predictions 9 of the Preferred Period Hypothesis, which suggests that both perceptual and motor rhythmic 10 behaviors are biased towards a specific personal 'default' tempo. To this end, we tested a 11 several aspects of rhythmic behavior, including spontaneous motor tapping (SMT), perceptual 12 preferences (PPT) and synchronization-continuations tapping in a broad range of rhythms, 13 from sub-second to supra-second rates. Moreover, we evaluate the intra-subject consistency of 14 rhythmic preferences, as a means for testing the reality and reliability of personal 'default-15 rhythms'. 1617 Results indicate that individuals with ADHD are primarily challenged in producing self-18 generating isochronous motor rhythms, during both spontaneous and memory-paced tapping. 19 However, they nonetheless exhibit a high degree of flexibility in synchronizing to a broad range 20 of external rhythms. These findings suggest that auditory-motor entrainment is preserved in 21 ADHD, and that the presence of an external pacer allows overcoming the inherent difficulty in 22 Some have argued that these default motor preferences also extend to the realm of auditory 64 perception. Specifically, McAuley and colleagues (2006) report a one-to-one correspondence 65 between individual SMTs and the tempo that individuals indicate is most 'comfortable' for 66 them to listen to, labeled their Preferred Perceptual Tempo (PPT). This finding prompted 67 the Preferred Period Hypothesis, suggesting that individuals have a characteristic preferred 68 rhythm, that is generalized across perception and production, and can be attributed to a 69 common internal oscillator (McAuley 2010;Michaelis et al. 2014;Provasi et al. 2014; 70 Schwartze and Kotz 2015). Moreover, according to this perspective, preferred internal rhythms 71 also influence behavior, facilitating perceptual, motor and inter-personal synchronization at 72 rhythms near one's SMT (Styns and Leman 2007;Large and Gray 2015;Zamm et al. 2015). 73 However, to date, the consistency of 'default' motor and perceptual preferences within 74 individuals and the degree to which they indeed generalize across rhythmic behaviors, has been 75 somewhat debated (van der Wel et al. 2009;McPherson et al. 2018;Qi et al. 2019). Moreover, 76 the manifestation of internal motor and perceptual rhythmic preferences in clinical populations 77 who exhibit timing-related de...