Cardiac synchrony in same-generation and intergenerational dyads: a longitudinal fNIRS study

Objectives

The study aimed to:

• Examine changes in cardiac synchrony across six sessions
• Assess relationships between collaboration, social closeness, and interpersonal distance
• Compare these measures between intergenerational and same-generation dyads

Study Design and Participants

The study included 122 participants, forming:

• 31 intergenerational dyads (older adults aged 69+ and younger adults aged 18–35)
• 30 same-generation dyads (younger adults only)

All participants were initially strangers and interacted with the same partner across six weekly sessions.

Methodology

Each session combined structured tasks, self-report measures, and multimodal recordings.

Tasks and Behavioral Measures

Participants completed:

• Individual and collaborative drawing tasks
• Weekly collaborative activities (including a jigsaw puzzle task)

Behavioral measures included:

• External ratings of drawing collaboration
• Puzzle task performance
• Interpersonal distance, estimated from motion tracking data

Self-Report Measures

Social closeness was assessed using the Inclusion of Other in Self (IOS) scale.

Measurement Tools

The study applied a multimodal hyperscanning approach using:

• Functional near-infrared spectroscopy (fNIRS) using Cortivision Photon Cap to record cortical hemodynamic activity
• fNIRS-derived signals to estimate inter-beat intervals (IBI) for cardiac synchrony analysis
• Video recordings and OpenPose-based motion tracking to quantify interpersonal distance

Cardiac synchrony was calculated using cross-correlation of IBI time series across time lags.

Results

Behavioral and Social Measures

• Intergenerational dyads showed higher levels of collaboration in drawing tasks compared to same-generation dyads
• Same-generation dyads performed better in the puzzle task
• Social closeness increased across sessions in both groups

Relationships between measures differed between groups:

• In intergenerational dyads, closer interpersonal distance was associated with higher collaboration and greater social closeness
• In same-generation dyads, interpersonal distance showed different patterns of association with these measures

Cardiac Synchrony

The analyses showed that:

• Cardiac synchrony did not differ substantially between intergenerational and same-generation dyads
• No substantial differences were observed between collaborative and individual tasks
• Cardiac synchrony did not show substantial relationships with collaboration, social closeness, or interpersonal distance

Additionally, no substantial differences were found between real and pseudo dyads.

A trend-level association between drawing collaboration and cardiac synchrony was observed in intergenerational dyads across most time lags.

Conclusion

The study indicates that collaborative behavior and self-reported social closeness provide more consistent information about relationship development than cardiac synchrony in this context.

Cardiac synchrony did not show substantial associations with behavioral or social measures across repeated interactions, although a trend-level relationship with collaboration was observed in intergenerational dyads.

Source

Based on: Moffat, R., Naudszus, L. A., & Cross, E. S. (2026). Cardiac Synchrony During Collaborative Drawing: A Longitudinal Comparison of Same Generation and Intergenerational Dyads. New York Academy of Sciences:

Learn more about Photon Cap in hyperscanning research

The study utilized fNIRS technology to capture brain activity during naturalistic interaction. If you’re interested in how Photon Cap supports this type of research, check out our previous article: Hyperscanning with the Photon Cap: The Role of Neural Synchrony During Social Interaction