By Emma Young
You spend about 10 per cent of your waking hours with your eyes shut, simply because of blinking. Every few seconds, each time you blink, your retinas are deprived of visual input for a period lasting anywhere between tens to hundreds of milliseconds (500 milliseconds is equivalent to half a second). You don’t usually notice this, because your brain suppresses the dark spells and stitches together the bursts of visual information seamlessly. But these dips in visual processing in the brain do have an impact: a new study in Psychological Science finds that, in an important way, they cause your sense of the passing of time to stop temporarily.
Exactly how we perceive the passing of time has not been established, and just how important ongoing sensory processing might be is debated. The new work confirms that visual processing has an influence. “In finding that we lose time when we blink, we essentially can draw a link between early ongoing visual processing and the sense of time,” says Ayelet Landau at the Hebrew University of Jerusalem, senior author on the study.
Laundau and her colleagues, including first author Shany Grossman at the Weizmann Institute of Science, recruited 22 participant to complete a visual challenge, while 23 others completed an auditory task.
Before the visual challenge started, the participants were first shown a white circle for either a “short” period (0.6 seconds) or a “long” period (2.8 seconds). Then came the actual challenge – they were shown a white circle on a screen for varying periods of time, and asked to judge whether the duration of each appearance was closer to the “short” or “long” period. The participants in the auditory group took part in a similar challenge, except that they had to judge the durations of bursts of white noise. For both groups, a video-based eye tracker continuously measured their eye position and pupil diameter throughout the tasks.
The participants’ judgments during the visual task showed how blinks affect our sense of time. Specifically, participants underestimated the duration of the white circle’s appearance if they blinked while they were watching it. What’s more, for each individual, the duration of this blink correlated with their degree of time under-estimation. There was, as the researchers write, “a proportional relation between the objective duration of sensory-input loss and the loss of subjective time.” These results, they go on, can be interpreted as “supporting a central role for ongoing sensory encoding in the subjective sense of time.”
For the auditory group, in contrast, blinking had no impact on their judgements of noise durations.
In the real world, we often use many senses to process what’s going on. If we’re watching someone talking while listening to them, for example, would blinking have any effect on our perception of how long they spoke for? This kind of work has yet to be done. “One possibility is that during periods of missing information from one sense, only information flow in the other sense will take over our sense of time,” Landau suggests. “Another option is that if one sense is more highly weighted by the brain — as is the case for vision in watching a person speak — subjective time will rely primarily on this sense and will therefore be distorted by information loss in this sense.”
The study raises all kinds of fascinating questions for future research to investigate. Right now, I’m sitting at my desk, focusing on my computer screen — relying heavily on vision. Yes, I’m absorbed in what I’m doing. But is one reason why time seems to go more quickly when I’m working because my blinks are affecting my judgements of time passing, but when I’m outside, hanging out with my kids, other types of sensory input are preventing or counteracting the time-compressing blink-effect?
The research team is currently planning studies to investigate how multi-sensory processing impacts subjective time — so watch this space. But, “we would expect subjective time to be primarily informed by the sense we are [currently] focusing on,” Landau says.
One final note: other ingenious studies have shown that it’s not the lack of stimulation of the retina, per se, that will alter time perception, but rather the dampening of activity in the visual cortex – a process triggered automatically by involuntary blinking (and which contributes to our seamless visual experience). This means that, should you wish to suspend time deliberately, opening and closing your eyes on purpose will not have the desired effect.