🧠 neuroscience

Preserved Spontaneous Interpersonal Entrainment during Rhythmic Synchronization in Autism Spectrum Disorder

This study demonstrates that autistic and neurotypical young adults exhibit comparable spontaneous interpersonal entrainment and sensitivity to visual social cues during rhythmic synchronization, suggesting that atypicalities in ASD may be selective rather than generalized.

Original authors: Denis, M., Rosso, M., Da Fonseca, D., Schön, D.

Published 2026-07-14

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CC BY 4.0

Original authors: Denis, M., Rosso, M., Da Fonseca, D., Schön, D.

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

Imagine two people trying to tap their fingers to a beat. Now, imagine one of them is secretly watching the other person tap, even though they are told to ignore it and focus only on their own sound. This is exactly what happened in a new study involving 24 young adults with Autism Spectrum Disorder (ASD) and 22 neurotypical young adults. The researchers wanted to see if the "secret watcher" would accidentally get their rhythm mixed up with the person they were watching, and if this happened differently for autistic people compared to everyone else.

The Setup: A Drifting Beat
Think of the experiment like a game of "follow the leader," but with a twist. Everyone had headphones playing a steady metronome click. The participants tapped their fingers to match that click. But here's the trick: the metronome wasn't perfectly steady. It slowly drifted, like a clock that gains or loses a tiny bit of time every second, completing a full cycle of this drift every 39 seconds.

In one version of the game (the "uncoupled" round), participants looked at their own hands. In the other version (the "coupled" round), they were told to look at the experimenter's hand, which was tapping to a slightly different tempo. They were explicitly told to ignore the visual movement and stick to their own sound. It's like trying to walk in a straight line while watching someone else walk in a zigzag; your brain might get confused and try to sync up with the zigzag anyway.

The Big Surprise: Everyone Got "Glued" Together
The main finding is a bit of a plot twist. Many people assume that autistic individuals might struggle to sync up with others, perhaps because their brains process visual and sound information differently. However, this study suggests that in this specific, calm, and predictable setting, autistic and neurotypical participants reacted in the exact same way.

When the participants could see the other person's hand, two things happened to both groups:

Their tapping got a little wobbly. Just like trying to walk a tightrope while watching a clown, their timing became less steady. The study measured this as an increase in tapping variability.
They secretly synced up. Even though they were told to ignore the other person, their tapping rhythms started to align with the experimenter's movements. This is called "interpersonal entrainment." It's as if their brains had an invisible rubber band connecting them to the person they were watching, pulling their rhythm toward the other person's beat.

The researchers found that this "rubber band" effect was just as strong for the autistic participants as it was for the neurotypical ones. The data showed that visual exposure increased the density of this coupled behavior, particularly when the two rhythms were close to being in perfect step (in-phase).

What This Rules Out
This study explicitly argues against the idea that autistic people have a broken or missing "social sync" button in their brains. Previous research had suggested that autistic individuals might have trouble with multisensory integration (mixing sight and sound) or predicting what others will do next. But in this specific experiment, those difficulties didn't show up. The paper suggests that the idea of a generalized inability to sync with others is likely too broad. Instead, it seems that when the environment is stable, slow, and predictable (like a 39-second drifting cycle), the ability to spontaneously sync up remains intact.

How Sure Are We?
The authors are careful not to call this a "cure" or a "fix." They use words like "suggests" and "supports accounts proposing." They measured real tapping data from 46 people and used complex math (computational modeling and recurrence analysis) to prove that the synchronization happened. They found that the visual cue made tapping less accurate but more socially connected for everyone.

However, they also admit there are limits. The experiment was very controlled, like a lab simulation. It doesn't prove that autistic people will sync up perfectly in a chaotic, noisy, fast-paced real-world conversation. The study suggests that the mechanism for low-level syncing is preserved, but it might only work well when the "traffic" on the road is light and predictable.

The Takeaway
So, if you imagine the brain as a radio, this study suggests that for autistic people, the radio isn't broken; it just might need a clearer signal to tune in perfectly. When the signal is clear and the rhythm is slow, the brain naturally locks onto the beat of the person next to them, just like anyone else's brain does. The "glue" that connects us to others through rhythm is still there, working just as well as it does for everyone else, at least in this quiet, rhythmic world.

Technical Summary: Preserved Spontaneous Interpersonal Entrainment during Rhythmic Synchronization in Autism Spectrum Disorder

Problem Statement
Interpersonal entrainment—the tendency of interacting individuals to temporally align their behaviors—is a fundamental mechanism for successful social interaction, relying heavily on multisensory integration and predictive processing. Autism Spectrum Disorder (ASD) is characterized by social communication difficulties and has been associated with atypicalities in predictive coding and multisensory integration. Previous literature suggests that individuals with ASD may exhibit increased tapping variability, reduced error correction, and atypical interpersonal synchronization during both intentional and spontaneous rhythmic tasks. However, findings in this domain remain mixed. The central problem addressed by this study is whether spontaneous interpersonal entrainment is globally impaired in ASD or if such atypicalities are selective, emerging primarily under specific interactional conditions (e.g., high complexity or rapid dynamics).

Methodology
The study employed a unidirectional adaptation of the "drifting metronomes" paradigm (Rosso et al., 2021) to assess spontaneous interpersonal coupling in 24 young adults with ASD and 22 neurotypical controls.

Experimental Design: Participants synchronized finger tapping with an auditory metronome (1.67 Hz) while an experimenter tapped to a slightly different tempo (1.64 Hz). The metronome phases drifted in regular steps, completing a cycle every 39 seconds.
Conditions:
1. Uncoupled (Baseline): Participants tapped while looking at their own hand; the experimenter's hand was hidden.
2. Unidirectional Visual Coupling: Participants tapped while visually observing the experimenter's hand movements but were instructed to ignore them and maintain synchronization with their own metronome. The experimenter could not see the participant, ensuring the visual influence was strictly unidirectional.
Measures:
- Individual Performance: Asynchrony (mean and standard deviation), tapping consistency (circular statistics), and computational modeling of sensorimotor synchronization (estimating timekeeper noise, motor noise, and phase correction $\alpha$ ).
- Dyadic Dynamics: Joint recurrence analysis (JRA) was used to quantify spontaneous interpersonal entrainment by calculating the density of simultaneous recurrences in the time series of the dyad.
Statistical Analysis: Linear mixed-effects models and Bayesian mixed-effects analyses were used to evaluate the effects of Group (ASD vs. Control), Condition (Coupled vs. Uncoupled), and their interactions on synchronization metrics and recurrence scores.

Key Contributions
This study contributes a refined investigation into spontaneous (non-intentional) interpersonal coupling in ASD, distinguishing between individual synchronization stability and dyadic coordination dynamics. By utilizing a unidirectional paradigm where the partner's movements are task-irrelevant, the authors isolate low-level sensorimotor coupling mechanisms from higher-order social intentions. The study also integrates computational modeling of phase correction with non-linear recurrence analysis to provide a multi-faceted view of temporal coordination.

Results

Individual Synchronization: Visual exposure to the partner's movements significantly increased tapping variability (higher asynchrony SD) and reduced tapping consistency (lower circular $R$ ) for all participants. Crucially, these effects did not differ between the ASD and neurotypical groups.
Phase Correction: Computational modeling revealed that phase correction ( $\alpha$ ) was significantly reduced in the coupled condition compared to the uncoupled condition, indicating that visual distraction interfered with the ability to correct timing errors. This modulation was comparable across both groups.
Dyadic Coordination: Joint recurrence analysis showed that visual coupling significantly increased recurrence scores (indicating stronger spontaneous entrainment) compared to the uncoupled condition. This enhancement was phase-dependent, with stronger entrainment observed around in-phase attractor regions.
Group Differences: No significant Group $\times$ Coupling interactions were found for any measure. Both ASD and neurotypical participants demonstrated similar sensitivity to spontaneous low-level interpersonal coupling, showing comparable increases in dyadic entrainment and similar disruptions in individual synchronization stability when exposed to visual motion.

Significance and Claims
The authors claim that these findings challenge generalized interpretations of predictive processing deficits in ASD. Instead, the results support accounts proposing selective rather than generalized atypicalities. Specifically, the study suggests that low-level spontaneous interpersonal entrainment mechanisms are preserved in ASD when interaction dynamics are stable, predictable, and evolve slowly (as in the 39-second drifting cycle).

The paper posits that atypicalities in ASD may emerge primarily in contexts requiring rapid online adaptation to complex or highly dynamic multimodal information, rather than in stable rhythmic contexts. Consequently, the authors suggest that spontaneous low-level coordination may act as a scaffold for higher-order social coordination in ASD, particularly in predictable interactional settings. The study concludes that while visual coupling disrupts individual synchronization stability, it simultaneously enhances dyadic entrainment in both groups, indicating that the fundamental mechanisms supporting spontaneous interpersonal coupling remain intact in ASD under these controlled conditions.

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