A clock and a gyroscope
Your sense of time is not a single function. It is deeply connected to your physical presence in the world, specifically to your sense of balance. The brain's timing mechanisms appear to be linked to the vestibular system, the set of structures in the inner ear responsible for detecting motion and gravity. This system includes the three semicircular canals, which detect rotational movements, and the two otolith organs (the utricle and saccule), which sense linear acceleration and the constant pull of gravity. Together, they provide the brain with a continuous stream of information about the body's orientation in space.
Researchers in Hamburg and elsewhere explore this connection using a technique called Galvanic Vestibular Stimulation (GVS). GVS involves placing electrodes on the mastoid processes—the bumps behind the ears—and passing a weak, painless electrical current between them. This current stimulates the vestibular nerves, creating a false sensation of movement even when a person is sitting perfectly still. The polarity of the current determines the nature of the illusion; placing the anode (positive electrode) on one side and the cathode (negative electrode) on the other causes the brain to interpret the imbalance as a head tilt or rotation that isn't actually happening. This method allows for precise, controlled activation of the balance system, independent of any real motion.
Hamburg's time-bending experiments
Neuroscientists at the University Medical Center Hamburg-Eppendorf (UKE) have used GVS to demonstrate how directly the vestibular system influences time perception. In these experiments, participants receive GVS while performing temporal judgment tasks, such as estimating the duration of a sound or a visual cue. The results show that vestibular stimulation systematically distorts their sense of time. When the vestibular system is artificially activated, participants' estimates of time intervals become less accurate.
The stimulation seems to cause a contraction of subjective time. Studies involving passive motion, such as being on a swing or a rotating chair, found that people produced longer intervals when asked to estimate a set duration, which indicates they perceived time as moving more slowly. One study noted that the over-production of time could be as high as 25% for a 5-second interval during passive stimulation. This effect is not believed to be caused by changes in attention or arousal, but by a direct influence on the brain's internal time-keeping networks. The cerebellum, a brain region involved in both vestibular processing and timing, is a likely site for this interaction. This research shows that the raw data used to build our sense of orientation is also a component in how we measure the flow of time.