Just testing your brain power. We are all getting a little concerned it seems about our mental agility as we get older. Why else would millions of us spend a Saturday night with Anne Robinson wrestling with the price of two bread rolls and a litre of milk but to reassure ourselves that we could apply to Mensa if we really wanted.

So how old is an adult, and how old is old? We are becoming adults at a later age, apparently. That probably means old age will be delayed indefinitely. According to American research, we have carved out a period of extended adolescence. As more and more of us are swept into further and higher education, we are delaying grown-up commitments like marriage and starting a family. Adulthood is closing in at around 26.

So you wake up on your 26th birthday and wham! Full adulthood, maturity, a paid-up member of society. Choose a mortgage, choose a washing machine, choose a three-piece suite . . . Irvine Welsh’s Renton may have eschewed such choices, but most of us equate adulthood with independence and the freedom to worry about plumbing and bills and will the dog like the baby.

But do you ever feel old enough to burn the bridges you have to burn? And as you get older, doesn’t everybody find themselves facing life experiences that they thought only grown-ups had to face? Admit it. Do you know anybody who would honestly classify themselves as adult?

Now the second part of the question. If you’re an adult at 26, when do you become old? As the baby-boomers hit their fifties, they’re pretty certain old is a long way off. Haven’t they watched their diets, jogged to the gym and honed their bodies? The latest craze in America is the brain gym.

Flabby brain? Try our six-week brain workout!

Americans are keen to stay sharp-witted. There is no real scientific evidence to support the theory that brain exercises will have any significant long term effect, but caged mice given toys did develop a mental six-pack.

Our college has an ad in the local paper today aimed at “silver surfers”, encouraging those over 50 to come to college and use the internet. I’m sure it will be hugely successful, but I have to question the epithet “silver surfers” applied to striplings. The marketing people used to call this the “grey market”, but that’s a misnomer as well when most are dying their hair purple.

Whatever the difficulties in describing this target group, we in further education are delighted to welcome the growing army of retired people who want to take up new interests, who want to learn new skills, who are, in fact, looking for the equivalent of a brain gym and are keen to develop mental muscle.

I’ve been pondering this adultold question because one of the learners in my Thursday creative writing class is a finalist in this year’s Adult Learner of the Year celebrations. I reckon she can safely be called an adult, because she’s 92. But could we class her as old? She came to college to learn how to write her autobiography, and to begin the transition from marathon running, where she disciplined her body, to writing, where she disciplines her mind. A brain gym on Thursdays to complement her physical training schedule.

At 92, Jenny is a worthy finalist who has taken lifelong learning to heart.

Her next project? Don’t ask. A friend has egged her on to try another class our college offers - belly dancing.

Dr Carol Gow is a lecturer in media at Dundee College.