快猫短视频

When you move your body in time to a rhythm, your perception of time stretches and contracts. The finding might help us pin down which parts of the brain control our internal clocks.

鈥淒istortions of perceived time are coupled to the timing of your actions, which are dictated by an internal rhythm,鈥� says Alice Tomassini at the Italian Institute of Technology in Ferrara.

She and her colleagues asked 16 participants to listen to four rhythmical beats, each one second apart, and then tap out four additional beats with their finger to keep the rhythm going. The participants were seated in a dark room at a desk on which there was a yellow LED light. Before the tapping test, the participants were taught to familiarise themselves with the way the yellow light would occasionally flash twice, with a 150-millisecond gap between the two flashes.

During the test, the yellow light flashed twice after a participant鈥檚 third finger tap but before the fourth. The gap between flashes varied from between 70 and 300 milliseconds, and participants were then asked to judge each time whether the gap between the flashes was longer or shorter than the 150 millisecond interval they had become familiar with.

There was an additional factor at play: sometimes the yellow light flashed twice just after a participant had made their third finger tap, sometimes just as they were preparing to make their fourth finger tap, and sometimes roughly halfway through the time interval between the two finger taps.

Time perception

Over 1000 trials per person, Tomassini and her team found that the participants tended to misjudge the length of the gap between yellow light flashes, but they did so in a predictable way. They consistently underestimated the length of the gap when the flashes were presented just after their third finger tap or just before the fourth finger tap, and overestimated the length of the gap when the flashes were half way through the interval between taps. In other words, participants perceived time to contract near the finger taps, and to expand midway through the interval between taps.

Because the test included both auditory and visual stimuli, it can help us tease out which parts of the brain are important for judging time. 鈥淥ur brain deals with multiple timing mechanisms. There is not one single clock,鈥� says Tomassini. But the experiment hints that the separate clocks are linked 鈥� and that our motor system, controlling muscles, may act as the master clock. To use an analogy, if our visual system is the string section of an orchestra and the auditory system is the brass section, the motor system might be the conductor.

The participants were not trained musicians, but Tomassini says she would expect that people trained to be more accurate with timing might not experience the time dilations as strongly.