Gravity is an ever-present force that has shaped the evolution of physiological and cognitive processes (Adamopoulos et al., 2021; Morey-Holton, 2003). However, humans increasingly encounter environments where gravity conditions differ from Earth's through parabolic flights and space travel, as well as analogous experiences in virtual or augmented reality (VR/AR). These scenarios provide novel interactions with altered gravitational cues, motivating a recent surge in scientific research on the perceptual and biological effects of such alterations. Existing reviews have focused on how Earth's gravity influences aspects of perception and action, such as spatial orientation and motion (Dakin and Rosenberg, 2018; Jörges and López-Moliner, 2017; Lacquaniti et al., 2015; Zago and Lacquaniti, 2005). This review considers recent studies on how Earth-discrepant gravity influences time perception.

Accurate timing is crucial for predicting and coordinating movements in response to environmental stimuli (Breska and Ivry, 2018; Coull and Nobre, 2008; Herbst et al., 2022). Time perception may be distorted under various internal or external conditions, requiring adaptive strategies to achieve task goals. This is of practical consideration for aerospace training and preparation, as astronauts undertake complex tasks in altered-gravity environments. Despite the ubiquity and relevance of time as a feature of human behavior and cognition, much remains unknown about the psychological and neurological mechanisms of time perception, and even less is known about how these processes are affected by gravity. Understanding gravitational effects on time perception may provide insight into the underlying mechanisms of human timing under normal Earth gravity (1 g) conditions, as well as improving the health and performance of astronauts during and after space travel.

The goal of this preregistered review is to clarify patterns of results from empirical studies examining time perception in differing gravitational contexts and how physiological changes may mediate these perceptual effects to identify knowledge gaps and potential targets for future research. In the first section, we focus on recent evidence for gravitational effects on time perception across a variety of timing tasks. We consider the effects of altered gravitational cues on time perception contrasted against the temporal referent of persistent gravitational forces on Earth. Second, we focus on how transient or persistent physiological changes may be linked to altered time perception by reviewing relations between gravitational forces and neural and physiological processes relevant to timing and time perception. Finally, we discuss open questions and future directions for research.

Gravity affects our perception of time in two key ways: indirectly by influencing the motion of external objects in the world, or directly through changes in physiological or sensory inputs. A substantial body of evidence links the perception of visual object motion through space to time perception (e.g., Brown, 1995; Conway et al., 2016; He et al., 2023; Huang and Jones, 1982; Vidaud-Laperrière et al., 2022), with fewer studies considering the mediating role of gravity on this space-time relation (for a review see: Lacquaniti et al., 2015). From a Bayesian estimation framework, human development and evolution within Earth's gravity provides a strong prior for expected motion physics, and deviations from this prior may induce temporal errors (for review; Jörges and López-Moliner, 2017). Changes in gravitational forces, which are typically stable when at rest on Earth, can also cause physiological symptoms, such as those related to cephalic fluid shifts, affecting the optic and vestibular systems (Hallgren et al., 2016; Lawson et al., 2016; Mader et al., 2013; Norsk et al., 2015). Thus, studying how gravitational forces affect time perception can involve experimentally manipulating the motion kinematics of objects in the visual field or by altering vestibular or proprioceptive feedback. The studies reviewed in this section used various approaches to test time perception under different experimental gravitational environments, including simulated and real gravitational changes experienced by astronauts on the International Space Station (ISS) or during parabolic flight.

Of utmost consideration for understanding gravitational effects on time perception are potential neurological and physiological mediators. Increases and decreases in gravitational forces on the body cause physiological changes to cardiovascular, vestibular, ocular, and somatosensory systems (Lee et al., 2020; Mergner and Rosemeier, 1998; Reschke and Clément, 2018b; Sarker et al., 2023). In astronauts exposed to different gravity conditions, changes include reduced heart rate and heart rate variability (Fritsch-Yelle et al., 1985; Migeotte et al., 2003; Otsuka et al., 2016), increased saccade latency (Reschke et al., 2017), and altered pupil activity associated with increased intracranial pressure and spaceflight-associated neuro-ocular syndrome (Lee et al., 2020; Sarker et al., 2023). Such bodily functions have been associated with timing processes; thus, altered gravity may affect time perception mechanisms directly or indirectly through neurophysiological mediators.

Much remains unknown regarding the effects of altered gravity on time perception via psychological or neurophysiological changes. Although there is a growing literature on gravitational effects on human physiological and perceptual functions, most studies have examined these effects in isolation, requiring causal inferences between relevant changes. Future studies should directly examine the roles of vestibular, visual, and interoceptive systems in time perception under altered gravity. Multimodal neuroimaging and electrophysiological studies during space missions and analog environments could clarify the underlying neural and physiological mechanisms of timing. Longitudinal monitoring of astronauts before, during, and after flight is essential to characterize adaptive changes in temporal processing and recovery. Including cross-modal timing tasks spanning visual, auditory, and tactile domains will help reveal how gravity-related sensory alterations shape integrated time perception. Further, ecologically valid tasks that mimic activities undertaken by astronauts on spaceflight missions will increase the translational relevance of findings.

Continued development and testing of countermeasures such as immersive VR or physiological feedback protocols will be important from both basic and applied scientific perspectives. Considering studies under real gravitational manipulations, isolating sensory and physiological effects using simulations may help disentangle contributions of different sources of information such as visual dynamics and vestibular inputs. Altered gravity not only causes astronauts to feel the effects of changes in vestibular inputs but also fundamentally changes the nature of how objects move around the visual field. VR/AR studies provide an avenue for testing the effects of visual gravitational changes on time perception in the absence of vestibular alteration. Understanding the connection between gravity-based changes and visual information is crucial not only because of physiological impacts on the visual system (Lee et al., 2020; Reschke et al., 2017; Sarker et al., 2023), but because visual object motion directly modulates time perception for stimuli within and across modalities (Brown, 1995; He et al., 2023).

Future studies should go beyond vestibular and proprioceptive to consider auditory, tactile, and interoceptive signals in gravity-modulated timing. Multisensory tasks can distinguish modality-specific from shared effects. How gravity interacts with affective and cognitive states, such as stress or motivation, also warrants attention. Active timing (timed motor actions) should be contrasted with passive timing (perception without action), as altered gravity may affect motor-perceptual integration differently from perception alone. With growing potential for space missions to extend in duration and distance, the systematic investigation of longer timescales should be undertaken. Most prior work has focused on brief (milliseconds-seconds) or intermediate (seconds-minutes) intervals, leaving hours-to-days durations relatively unexplored. Examining circadian (24-h) and ultradian (less than 24-h) rhythms in altered gravity will further clarify mechanisms governing timing across scales.

Finally, advancing formal computational models should explicitly incorporate gravity as a parameter in timing mechanisms. Such models should account for dynamic re-weighting of multisensory inputs, particularly vestibular, visual, proprioceptive, and interoceptive signals, when reliability changes under different gravitational conditions. Bayesian perceptual inference (Jörges and López-Moliner, 2017, 2020; Allred et al., 2023), Bayesian Prediction Error Minimization (PEM; i.e., “distrusting the present”; Kent et al., 2019), and predictive-processing frameworks (Millidge et al., 2024) offer promising foundations as they can simulate how altered gravity introduces temporal biases by modifying prediction errors and sensory precision estimates. State-space adaptation models (e.g., Ravichandran-Schmidt and Hass, 2024) may further help chart how perceptual timing recalibrates over longer missions and, once astronauts return to Earth, predict trajectories of learning, compensation, and recovery.

In conclusion, growing evidence highlights that altered gravity profoundly influences perceptual, neural, and physiological substrates of human timing. These changes manifest as distortions in subjective timing, variability in temporal accuracy, and recalibration of sensorimotor integration. Understanding how gravity reshapes time perception not only informs fundamental cognitive neuroscience but is critical for astronaut performance and wellbeing during long-duration space missions. Continued interdisciplinary research integrating psychology, neurophysiology, vestibular science, and medicine is vital to unraveling these complex processes and to developing effective countermeasures for the challenges of human activities beyond Earth. Such studies may also extend beyond space exploration, offering translational benefits for clinical neuroscience. Simulations such as VR/AR can be harnessed for rehabilitation protocols that allow patients with motor, vestibular, or perceptual disorders to relearn and practice timing-dependent skills in controlled, adaptive environments. In this way, research on gravity and time perception not only advances our readiness for future spaceflight but also enriches therapeutic strategies to support recovery and functional independence on Earth.