Is your memory playing tricks on you, or did you find shopping at your over-priced supermarket last week a wonderful experience? Did you have a great time on that lacklustre package holiday a couple of years ago? And are you quite sure whether you enjoyed that cold, tasteless meal the other day?
Advertisers have found a new way to mess with your mind.
A group of US marketing researchers claim that brand owners can make their customers believe they had a better experience of a product or service than they really did by bombarding them with positive messages after the event. Advocates of the technique, known as "memory morphing", claim it can be used to improve customers' perceptions of products and encourage them to repeat their purchases and recommend brands to friends.
Its chief cheerleader is Professor Jerry Zaltman, a psychologist attached to Harvard Business School. He claims that advertising - "if properly constructed" - can lead to the creation of false memories.
"When asked, many consumers insist that they rely primarily on their own first-hand experience with products - not advertising - in making purchasing decisions. Yet, clearly, advertising can strongly alter what consumers remember about their past, and thus influence their behaviours," he writes in his book, How Customers Think. He says that memories are malleable, changing every time they come to mind, and that brands can use this to their advantage. "What consumers recall about prior product or shopping experiences will differ from their actual experiences if marketers refer to those past experiences in positive ways," he continues.
Zaltman has worked in the past with many big brand owners, such as Coca-Cola, Nestlé, Procter & Gamble, Motorola, Reebok and General Motors, though it is not known whether his advice covered memory morphing.
But Coca-Cola's UK president, Tom Long, speaking at a marketing conference earlier this year, seemed to get close to giving his seal of approval to the technique. He said that memory morphing "is something Coca-Cola was pleased to learn [about]." And he went on to advise marketers: "Try to morph the memory of your consumers."
British advertising agencies say Zaltman has contacted them offering advice on how to use memory morphing techniques. But none of the agencies contacted by The Independent has admitted taking up the offer.
Zaltman's extraordinary claims are based on experiments carried out by memory researchers in the US, most notably the work carried out by Elizabeth Loftus, a former professor of psychology at the University of Washington. She singled out a campaign by Disney - "Remember the magic" - which, she claimed, was used to invoke real or imaginary childhood memories in consumers.
She reported an experiment in which people were shown an advert suggesting that children who visited Disneyland had the opportunity to shake hands with Bugs Bunny. Later, many of those who had seen the advert "remembered" meeting Bugs on childhood visits to the theme park, a feat that would have been impossible, given that the cartoon is a Warner Brothers character. Loftus said: "This brings forth ethical considerations. Is it OK for marketers to knowingly manipulate consumers' pasts?"
Earlier this year, other American psychologists announced research findings to the American Association for the Advancement of Science, showing the ease with which false memories can be implanted in people's minds. In a test by the cognitive psychologist Kathryn Braun-LaTour, a colleague of Zaltman's, participants were served an unpleasant-tasting orange drink spiked with salt and vinegar. They were then shown adverts suggesting the drink was refreshing. Sure enough, many of the participants later reported that they had found the drink refreshing.
While most experts deny that brands actively use memory morphing in their advertising, some believe it may be an inadvertent consequence. Erik du Plessis, chief executive of the South African arm of the world's leading advertising research firm, Millward Brown, has just written his own book on the psychological effects of advertising called The Advertised Mind.
He says: "There is evidence that memory morphing might happen, though I don't think anyone has actively tried to use it. Certainly some advertisements I have seen have a very good chance of doing it. There is advertising I can see that reminds me of good times I have had. I will probably remember the brand as having been there, although it might not have been." But he believes morphing can only take place in a "credible" way. If consumers have had a bad experience, it will be impossible to turn that into a positive memory.
Mark Earls, planning director of the advertising agency Ogilvy London, says Zaltman is promoting memory morphing as a research tool to help brand owners decide which adverts will be successful. If an ad can be shown to change people's memories of past experiences, this indicates it is very powerful. But he is sceptical about Zaltman's methods.
"The advance they are claiming to have made is in being able to monitor the brain as opposed to the mind, and measure the ways our brain changes when exposed to advertising. But this is old-fashioned.
"What is important these days is not what advertising does to consumers, so much as how consumers use advertising to make statements about themselves to other people," concludes Earls.
Zaltman may be portrayed as a maverick whose ideas are irrelevant to modern advertising. But he argues that significant advances have been made in neuroscience over the past 10 years, and he believes that the unconscious mind is a great unexplored area for marketers.
But will he persuade an industry that knows it would face a public outcry if consumers found out advertisers were using his technique? Perhaps not.
Richard Huntington, head of planning at the agency HHCL/Red Cell, says: "It is the last refuge of the scoundrel to say that there's bugger all we can tell you about this product, so we'll pretend that you all had great Christmases."