They used to think goldfish had the shortest memory span in the world until some psychologist's life's work claimed it might well be three months rather than three seconds.
If that is the case, then it is a good deal longer than some footballers.
Take Liverpool's Javier Mascherano and Stoke's Asmir Begovic, for instance.
Mascherano was so desperate to get away from Anfield that he was left out of Monday's 3-0 defeat by Manchester City because he was said not to be in the right frame of mind. Begovic, meanwhile, was reported to have refused to play in the Carling Cup against Shrewsbury after Stoke turned down two bids from Chelsea.
Former England manager Graham Taylor described their actions, or inaction, as "tantamount to treason".
We prefer to call it the selfish, self-centred, self-obsessed actions of footballers who no longer recognise the line between right and wrong.
No one would argue that Mascherano's desire to go to Barcelona was not understandable. It is a wonderful club, his family have not settled in England. It is his dream move.
But that is where memory, or the lack of it, comes in. Conveniently, Mascherano has forgotten what Liverpool did for him. What they did when he was the forgotten foreigner at West Ham in a first season in England where he made just five appearances for the Hammers amid all the flying flak surrounding the issue of third-party ownership.
Real Madrid, Barcelona and Juventus were all linked with a potential move for him then but it was Liverpool who made it happen. It was Liverpool who re-energised his career to a point where he is now perceived as arguably the best holding midfielder in football.
It was Liverpool who took him from the Upton Park bench to the 2007 Champions League final in Athens against AC Milan.
Is it too much for Liverpool to ask for some loyalty in return? No one is asking him to buy a house on Scotty Road and sign for life, just give everything to the cause and shed every drop of sweat while still contracted to wear the famous red shirt.
The same goes for Begovic, potentially one of the best young goalkeepers in the Premier League but who was stranded on the bench at Portsmouth, watching the financial conflagration sweeping through a proud old club, last January when Stoke performed an emergency evacuation.
Yes, the lure of a job at Premier League champions Chelsea must be strong, but he is contracted to play for Stoke. They pay his wages. They deserve a full and committed shift in return.
In most walks of life Mascherano and Begovic would be fingering their P45s and on the way to the job centre. In the world of football that rarely happens.
Why? Because players are not just employees. They are also major company assets. Mascherano might well bring in £25million, which means managers such as Roy Hodgson have to bite their tongue. Be diplomatic. Do nothing to devalue that asset.
It is player power at its worst and one of the ugliest scars on the game.
In the interests of fairness it should be pointed out that it is not always like that. Arsenal's Cesc Fabregas was desperate to move to Barcelona, too, this summer. But he stayed because Arsenal wanted him to and he was contracted to them. He did not refuse to play. He vowed, in fact, to play as he has always done, with wholehearted endeavour and has been as good as his word, having made his name at Arsenal since joining them in his mid-teens.
A pity Mascherano and Begovic do not have such good memories.