Time perception

A complete theory of time perception will also have to explain why it is so flexible. Cocaine, amphetamine and nicotine have all been shown to speed up time perception, while some antipsychotic drugs slow it down. All interfere with the neurotransmitter dopamine. People with disorders in the dopamine system, such as those with Parkinson's disease or schizophrenia, also suffer distortions in their perception of time.
Time can be stretched and shrunk in other ways. It seems to slow down when you are frightened and flies when you are having fun. Time seems to pass more quickly as you get older.

The key to these puzzles may be how we think about how we perceive time. "We're under the illusion that time is just one thing, but we can take various aspects of time and manipulate them separately from the others," says David Eagleman of the Baylor College of Medicine in Houston, Texas. That might mean our perception of it also has several components.

The reason time seems to slow down, Eagleman suggests, is that intense or novel situations command our attention and cause our brains to soak up more detail. Eagleman has shown that when the brain is exposed to the same image over and over, and is then confronted with a different image, the new one seems to last longer, even though it is displayed for the same period of time. The brain also uses more energy when exposed to the new image. "The length of time something seems to have lasted appears to correlate with the amount of energy the brain uses to record an event," Eagleman says.
This observation may also help explain why time speeds up as we get older. For children everything is new and the brain is processing vast amounts of information about the world. As we age and the brain has learned the rules of the world, it ceases to record as much information. "It is as if at the end of a summer you look back and you don't have that much footage, so it seems to have gone by more quickly," says Eagleman.

This might suggest that we can stretch our lifetimes by trying to pack as many different and exhilarating experiences into it as possible.
The trouble is just finding the time. .

based on an article by Linda Geddes in New Scientist no. 2833 (8 October 2011)