---
title: "When Wearables Distort Time: Unintended Effects of Haptic Heartbeat Biofeedback on Temporal Cognition and Motor Performance"
authors:
  - Andreia Valente
  - Mark Billinghurst
  - Augusto Esteves
year: 2026
venue: "Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies (IMWUT 2026)"
doi: "10.1145/3857955"
url: "https://andreia-valente.com/publications/valente2026wearables.html"
pdf: "https://andreia-valente.com/pdfs/valente2026wearables.pdf"
topics:
  - Haptic Biofeedback
  - Time Perception
  - Interoception
  - Neural Entrainment
  - Physiological Computing
  - Wearables
---

# When Wearables Distort Time: Unintended Effects of Haptic Heartbeat Biofeedback on Temporal Cognition and Motor Performance

## Citation Metadata

- Authors: Andreia Valente, Mark Billinghurst, Augusto Esteves
- Venue: ACM IMWUT 2026 (Proc. ACM Interact. Mob. Wearable Ubiquitous Technol., Vol. 10, No. 4, Article 256)
- Year: 2026
- DOI: https://doi.org/10.1145/3857955
- HTML: https://andreia-valente.com/publications/valente2026wearables.html
- PDF: https://andreia-valente.com/pdfs/valente2026wearables.pdf

## Plain-Language Summary

Wearable devices increasingly deliver heartbeat-like haptic feedback to help people calm down, focus, or perform, and designers usually treat that rhythm as a neutral background signal. This paper shows that the rhythm itself quietly reshapes how long time feels and how quickly people react. Participants wore an ankle device that pulsed at either 50 BPM or 100 BPM while estimating the duration of on-screen events and responding to stimuli, with heart rate and heart rate variability recorded throughout.

Slow feedback made time feel shorter (underestimation), fast feedback made it feel longer (overestimation) and lowered heart rate variability, and both rhythms sped up reaction times. The core message is cautionary: feedback frequency is a design parameter that shifts both temporal perception and motor readiness, not a neutral setting.

## Method

The study used a wearable ankle-mounted haptic device delivering heartbeat-like vibrations at two frequencies, 50 BPM and 100 BPM, compared against a no-feedback baseline. One task measured time estimation (judging the duration of a visual stimulus) and another measured reaction time. Heart rate and heart rate variability (HRV) were recorded from ECG so that behavioral effects could be separated from physiological ones. The study also examined whether synchronization between the artificial rhythm and the user's own cardiac cycle modulated the effects.

Rather than testing a single theory, the design evaluates three explanatory frameworks within the same participants by identifying conditions where their predictions diverge: interoceptive illusions (external stimuli create false perceptions of internal states) predict frequency-specific effects without physiological change; physiological modulation predicts coupled behavioral and autonomic shifts; and neural entrainment predicts rhythm-regularity benefits independent of frequency.

## Key Findings

- 50 BPM feedback led to systematic underestimation of time intervals, without accompanying changes in heart rate or HRV, consistent with a primarily perceptual (interoceptive illusion) account.
- 100 BPM feedback produced overestimation of durations alongside decreased heart rate variability, consistent with convergent interoceptive and physiological modulation.
- Both frequencies improved reaction times compared with no feedback, a benefit independent of rhythm speed and consistent with neural entrainment rather than arousal-based accounts.
- Preliminary observation (cardiac-phase attenuation): rhythmic feedback may reduce the natural cardiac-phase constraint on motor performance, where responses tend to be slower during systole. This pattern was not robust and is reported cautiously.

## Design Implications

Feedback frequency should be treated as a first-class design parameter for wearable haptic systems, not a neutral default. Slower rhythms can compress perceived time while faster rhythms can expand it, which matters directly for time-sensitive and safety-relevant contexts such as driving, sustained attention, and time-pressured tasks. Designers of biofeedback interventions for stress regulation or performance support should anticipate and evaluate these temporal and motor side effects, because the same feedback that aids self-regulation can also distort the user's sense of time and shift motor readiness.

## Why This Paper Matters

Wearable haptic heartbeat feedback is now widely deployed for stress regulation and performance support. This work provides empirical design knowledge showing that such feedback can unintentionally distort temporal cognition and motor readiness, and it frames feedback frequency as the primary lever, contributing to physiological computing, affective computing, interoceptive interfaces, and ubiquitous and wearable system design.

## Recommended Citation

Valente, A., Billinghurst, M., & Esteves, A. (2026). When wearables distort time: Unintended effects of haptic heartbeat biofeedback on temporal cognition and motor performance. Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies, 10(4), Article 256. https://doi.org/10.1145/3857955

```bibtex
@article{valente2026wearables,
  author    = {Valente, Andreia and Billinghurst, Mark and Esteves, Augusto},
  title     = {When Wearables Distort Time: Unintended Effects of Haptic Heartbeat Biofeedback on Temporal Cognition and Motor Performance},
  year      = {2026},
  month     = dec,
  journal   = {Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies},
  volume    = {10},
  number    = {4},
  articleno = {256},
  numpages  = {27},
  publisher = {Association for Computing Machinery},
  doi       = {10.1145/3857955},
  url       = {https://doi.org/10.1145/3857955}
}
```