Opening soon: the gallery of abandoned iPods, CDs, books . . .

WE EACH HAVE our personal museums to outdated formats. CDs we don't play any more; cassette tapes so old they would be chewed up by any player they were fed to; videotapes held on to even though there is no longer anything in the whole town left to play them on.

Each collection is ready to extend into a new wing, a new exhibition.

Opening soon: the DVD wing; the Memory Stick memorial; the gallery of abandoned iPods.

My museum doubles as the attic, which, as I guess is common, is already piled high with don't need it nows, might need it somedays, wait and see if we need it agains, Christmas decorations and mouse droppings. But the boxes of CDs have become a particular psychological burden. They are packed tight, stripped of the order they were once carefully allotted, so that Björk is wedged against Morrissey; Belle & Sebastian are getting intimate with DJ Shadow. Each ekes out its days here, in physical-copy purgatory.

They are held on to for reasons increasingly illogical. Over the summer I reached a point at which I pretty much stopped owning new music by signing up to a streaming service (Deezer. Other services are available), and there has been some coverage recently of how digital music, via iTunes and the like, is only really leasing music to the buyer anyway, so that your kids can't be the lucky beneficiaries of your computer's complete Phish collection. In opting for a streaming service I have finally relinquished even the veneer of ownership.

Yet still the CDs are kept; even cases empty of discs remain, holding a lonely vigil that someday they might be reunited with their long-lost contents.

These bits of plastic and paper hold an attachment that is clearly related not to the physical objects themselves but to the music they hold.

Music has long been a particular favourite for even the casual hoarder, because it is an exemplar of the idea that a collection is not simply about amassing stuff but is also a way of giving some structure, narrative and even meaning to one's life.

For many, books offer that too, and, as digital books gain ground, the day in the attic dawns for all those paperbacks. As it is, you can hardly give books away any more. Try your local charity shop: they often greet a box with a look of grief and a glance towards the already overstocked shelves.

Both music and books now challenge the impulse to hold on to something even when it is not special, when another version is available to be downloaded direct to you at almost any instant. There are several reasons why we do, of course, otherwise you wouldn't be sitting at home surrounded by CDs you don't play, arranging books you keep simply because to bin them would just feel plain wrong, even when we dump the printed words of magazines and papers every day.

It is partly down to what psychologists call the endowment effect, a sense that something is of value simply because you possess it. At Harvard they ran a test on this, handing mugs to some subjects and $6 to others. They found that the mug-owners would part with their mugs only for twice the amount that the cash-holders were prepared to pay for them.

A British psychologist and author, Tom Stafford, has written about how to reverse that instinct as a path to decluttering.

"Knowing the power of the bias, for each item I ask myself a simple question: If I didn't have this, how much effort would I put in to obtain it? And then more often or not I throw it away, concluding that if I didn't have it, I wouldn't want this."

There are other theories about hoarding in its most psychologically crippling forms - which have echoes even among the mainstream CD owner: the "compensation theory", in which objects make up for lack of self-worth, or collecting as "terror management" motivated by the fear of mortality.

Presumably, a genuine reluctance to part with the collected works of M People isn't seen as a proper disorder.

Either way, the results are the flotsam of pop culture and consumerism washed up in the attics and spare rooms of the first world, backwash from a cultural storm in which the physical format has risen and fallen almost within the average human lifespan. And they will be curiosities, relics, reminders of that brief time when a song could be trapped and held but whose chief function will be for your children to feel guilty about when they have to sort through your stuff someday after you're gone. "We should chuck it out. But it was Dad's . . ."

@shanehegarty