Time may seem like it’s racing by at a hastening pace as we age, but the reason isn’t based on a psychological reckoning with our impending mortality—it’s based on pure physics, since the aging brain experiences a decrease in its ability to process what the eye sees, a new study in European Review reports.¹

Study author Adrian Bejan, a professor of engineering and researcher at Duke University, said those long-held memories of one’s childhood stay vivid decades after they occur since children process images in a rapid-fire pace.² The result is a greater cumulative store of visual impressions in kids than older people experience, akin to how removing frames in a film strip will create the impression of increased speed.

The ‘time passing quickly’ phenomenon is based on physical changes in the aging human body, Prof. Bejan said in a Duke University release. When complex networks of nerves and neurons mature, they grow in size and complexity, leading to longer paths for signals to travel. As those paths age, they also degrade, giving more resistance to the flow of electrical signals, he noted.²

As people get older, the rate at which new mental images are acquired and processed declines. And since older people view fewer new images in the same amount of actual time, it may seem as though time is passing faster, the study reported.¹

“The human mind senses time changing when the perceived images change. The present is different from the past because the mental viewing has changed, not because somebody’s clock rings,” Prof. Bejan said in a Duke University release.²

For a more scientific explanation, the “mind time” is a sequence of images, such as reflections of nature that are fed by stimuli from sensory organs, Prof. Bejan wrote in his paper. The rate at which changes in mental images are perceived decreases with age, because of several physical features that change with age: saccades frequency, body size, pathways and degradation. The misalignment between mental-image time and clock time serves to unite the voluminous observations of this phenomenon in the literature with the constructal law of evolution of flow architecture, as physics, he added.^1,2