Weber’s Law: why time passes faster as we get older

Weber’s Law: why time passes faster as we get older


Our perception changes depending on whether the stimuli we are exposed to are large or small.

What happens when you enter a dark room and a candle is lit? You notice the flame on right away, right? And if that room is fully lit, how long can it take you to realize that there is a candle lighting up?

Almost in all likelihood much more than when there is barely a source of light.

The same thing happens with weight. A person can distinguish perfectly the difference of a weight of 100 grams of one of 120 but not so easily that of a 200 grams of one of 220. They are 20 grams of difference in the two cases, yes, but our perception is altered the ey Weber .

An algorithm

And it was Ernst Heinrich Weber, an acclaimed German doctor of the late nineteenth century who developed an important work in the fields of physiology and psychology, the first to realize this and translate this phenomenon into an equation or algorithm.

The formula was improved by a contemporary psychologist, also German, called Gustav Theodor Fechner, so the law could really be called Weber-Fechner but is better known by the name of the first.

Blackboard with equations
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Image caption Weber (and later Fechner) developed an equation to explain the phenomena and that today is used in marketing.


It is that when comparing two small stimuli, a minimum difference is enough to distinguish them perfectly. Now, if they are large, they must be very different from one another to be able to realize.

Therefore with the weights, although it is 20 grams of difference in both cases, it costs much less to distinguish the size difference in the smaller weights. And also with the candle and the illuminated room, where the stimulus and the source of light is greater.

Laboratory weights
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Image caption The more weight, the harder it is to appreciate the difference between masses, according to Weber’s Law.


The same thing happens with time, with size, with the height of things or with almost anything. Our perception changes and we find it more difficult to find differences in masses or larger units.

This law also explains why time accelerates when we get older.

“Although a year has always the same duration, the relationship between what lasts one and the time you’ve lived is getting smaller,” explains the mathematical disseminator Hannah Fry in a video on the YouTube channel of Numberphile, a specialized website in the science of numbers.

Drawing of a brain with a clock
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Image caption As the quantity or size increases, we increasingly appreciate the differences in time or weight.


That means that each year that passes adds perceptually less to the total of our life than a year when we are young children, which is why when we get older we get the feeling that time passes faster.

Fry also uses the example of prison sentences.

“A period of six months behind bars feels much more than a period of three, but a penalty of 20 years and three months is not perceived much more than another 20 years,” he explains.

In conclusion, when increasing the quantity or the size, each time we appreciate less the differences of time or weight.

Weber’s law in marketing

Doors of different sizes.
Copyright of the GETTY IMAGES image
Image caption According to the Webes law, it is much more difficult for us to perceive the changes of large stimuli than small ones.


According to Numberphile, this is a technique that companies use in their marketing work.

For example, they say that substantially increasing the price of very expensive products such as appliances or property is harder to detect than if the price of milk, bread or cheaper products rises.

Also, they say from Numberphile, they use it to reduce the size of the products that continue to maintain the same price. The decrease in the size of a chocolate tablet, for example, must be made very subtly and gradually so that the consumer does not perceive it.

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