It is a phenomenon that anybody beyond primary school age knows only too well. As a small child, an hour's enforced rest would stretch tortuously by; the soft-focus summers seemed to last an eternity. But these days time just seems to race past - and with each year it races a little faster. A day is gone, and then a week, almost before you've noticed.

The 19th-century psychologist and philosopher Paul Janet was perturbed by the sensation. "Whoever counts many lustra [five-year periods] in his memory need only question himself to find that the last of these - the past five years - have sped much more quickly than the preceding periods of equal amount," he wrote. "Let anyone remember his last eight or 10 school years: it is the space of a century. Compare with them the last eight or 10 years of life: it is the space of an hour."

Nostalgia and an increasing awareness of impending mortality probably accounts for much of this. But new research suggests that the experience of "time flying" as we get older could be much more than that: a fundamental component of the still-mysterious ways in which our brains perceive the passage of time.

Susan Crawley and Dr Linda Pring, two psychologists from Goldsmiths college in London, revealed their findings yesterday at the British Psychological Society's 1999 London conference, on the theme of time. True to form, the papers presented at the conference range from the stupe fyingly obvious to the genuinely intriguing - and the Goldsmiths research, contrary to first impressions, actually belongs in the latter category.

There is a population-wide tendency to believe that significant events - a death in the family, say, or a disaster in the news - happened more recently than they really did. But when Crawley and Pring asked people in different age groups to estimate how recently major public events took place, they discovered that this tendency - "forward telescoping", as psychologists prefer to call it - was significantly reduced among older people. And for the oldest subjects questioned, the phenomenon actually reversed: the over-60s tended, on average, to place events too distantly in the past. The results support earlier studies showing that younger adults can estimate much shorter passages of time - of the order of a few minutes - with much more accuracy than the elderly, who tend to overestimate.

"The idea that time flies as you get older is something you hear said casually every day, but in a legal or medical context the ability to estimate the passage of time can be crucial," says Crawley. "Many of our subjects said they found the task very difficult, and incredibly frustrating - they could remember the events very well, but had no way to place them in time. Often, they would have to stop and think of personal things they could use to date the events - what they were doing at the time, for example, or whom they talked about it with."

As a species, we have worried about the experience of the years slipping away at least since the 1500s, when Copernicus provided a convincing astronomical explanation for the passage of days and seasons. The Industrial Revolution - not to mention the invention of the alarm clock - exacerbated the obsession. But for a concern that is so old, psychology has been remarkably slow to investigate.

We know much about circadian rhythms - the bodily fluctuations in levels of the hormone-like substance melatonin, which regulates our daily sleep-wake cycle and is disrupted by transatlantic air travel - but almost nothing about how time is perceived over longer periods. At least part of the reason, Crawley suggests, is the modern psychological establishment's tendency to rely on readily available, cash-hungry students as subjects, thus ignoring the old.

"Psychologists have taken time for granted, or assumed that it's a neutral thing," says Dr Mark Levine of Lancaster university, attending the conference. "Subjective time is multiple, fragmented and contradictory; it's not just clock time. But most psychological research has tended to work with clock time alone. The more we measure and quantify time like this, the more it seems linear and straightforward - and the more it becomes divorced from time as we really experience it."

Moved, perhaps, by millennial preoccupations, a few scant details are beginning to emerge - and what we know so far suggests that time perception varies massively from person to person, moment to moment, culture to culture. Age is not the only factor: time seems to go faster when the body is colder and slower when it is warmer, for example; some studies have also suggested that our perception of clock time is much more accurate during sleep or hypnosis.

Excitement and arousal slow the experience of time: sports players report time slowing or standing still as they reach a crucial moment in a game, while road accident victims experience a "slow-motion" effect at the moment of impact. All these "slowing" experiences seem to correlate with abnormal concentrations of the neurotransmitter dopamine in the brain, but beyond that, the field remains a bewildering, uncharted one - even to the specialists.

Culture and nationality also seem to play a part, as Peter Collett, a research psychologist at the university of Oxford, who presented his research at the conference yesterday, discovered when questioning hundreds of managers in Britain, France, Germany, Bulgaria, Poland and the Czech Republic. To his surprise, the Germans - stereotypically obsessed with punctuality - proved least conscious of the passage of time. British managers reckoned employees were late for a meeting if they missed the starting time by eight minutes. The laid-back Germans only started to grow irritable after 15.

How warped is your perception of time?

The Goldsmiths researchers asked people of different ages to provide the month and year in which the following major events took place:

The 1990s
1 Margaret Thatcher resigns
2 The Windsor Castle fire
3 The channel tunnel opens
4 The Docklands bomb
5 The Dunblane massacre

The 1970s and 1980s
6 Margaret Thatcher becomes prime minister
7 John Lennon is assassinated
8 The Brighton Grand Hotel bomb
9 The Challenger space shuttle disaster
10 The Lockerbie bomb

Answers
1 November 1990
2 November 1992
3 May 1994
4 February 1996
5 March 1996
6 May 1979
7 December 1980
8 October 1984
9 January 1986
10 December 1988