Scientists may be closer to understanding why time seems to pass faster as we age – and brain scans of people watching an old Alfred Hitchcock show have helped them answer this lingering question.
In a study published on September 30 in the journal Communication biologythe scientists extracted data from the Cambridge Center for Aging and Neuroscience (Cam-CAN), a long-term research project on brain aging. A total of 577 people had already watched an extract from the old television series “Alfred Hitchcock Presents”, an eight-minute episode entitled “Bang! You’re Dead”. While study participants watched the clip, functional MRI scans (fMRI) were recorded; these analyzes would provide a measure of the evolution of participants’ brain activity over time.
At the time the brain scans were taken, the participants ranged in age from 18 to 88 years old. The researchers had access to these existing fMRI recordings and used something called Searching for Greedy State Boundaries (GSBS) to analyze them.
As its name suggests, this computer algorithm detects transitions between stable patterns of brain activity. He does so “greedily,” that is, he identifies these changes moment by moment, without taking into account the overall structure of the story on a longer time scale.
During the eight-minute clip, the older participants’ brains shifted to new states of activity less frequently, and these brain states lasted longer for them than for the younger participants. This trend was consistent across the 18 to 88 age range.
“This suggests that longer (and therefore fewer) neuronal states during the same period may contribute to older adults seeing time pass more quickly,” the researchers wrote in their report. This corresponds to an idea of time which dates back to Aristotle: The more notable events occur in a given period, the longer it subjectively seems. The new findings raise the possibility that if older people’s brains register fewer “events” in a given time frame, that may be why time seems to pass so quickly.
Although it’s only a hypothesis for now, “the idea that it might affect perception and memory in everyday life, including the feeling that subjective time seems to pass faster with age, seems very plausible to me,” said Giorgio Vallortigaraa neuroscientist from the University of Trento in Italy who was not involved in the new study.
The authors attributed their observations that older adults show fewer transitions between neural states to a phenomenon known as age-related neuronal dedifferentiation. In this process, the activity of different areas of the brain becomes less specific with age. For example, in young people, groups of neurons located in face-selective regions respond more selectively to faces as a category, but in older people, these groups of neurons fire more often for objects that are not faces. This generalization – to the level of larger groups of neurons rather than individual neurons – may be true for the brain as a whole and make it more difficult to recognize where one event ends and another begins, the study authors propose.
However, neuronal dedifferentiation may not fully explain why time passes quickly when we are older.
Joanna Szaduralinguist at Maria Curie-Skłodowska University in Poland, studies how language shapes our perception of time. She told Live Science that the scientists’ hypothesis is sound, but added that we also need to take into account that each of us has two time scales.
Society divides time linearly into hours, days and years, while our internal scale follows logarithmic laws. For example, a year so far represents 20% of the life of a 5-year-old child, but only 2% of that of a 50-year-old child. Therefore, time perception depends not only on the number of neural “events” in the brain, but also on the internal non-linear way in which we measure time.
The researchers noted that older adults may still be able to make their time seem subjectively fuller.
“Learning new things, traveling and engaging in new activities can help make time feel longer in retrospect,” study co-author Linda Geerligsresearcher at Radboud University in the Netherlands, told Live Science in an email. “But perhaps even more important are meaningful social interactions and activities that bring joy, which can also contribute to a better perception of time.”
