If only that very first bite of asparagus had inspired delight, and the first taste of jelly doughnut caused a stomachache. If children's happiest food memories were baked and not fried, leafy green rather than beefy, think of the difference in what people might eat.

Now, think of what it might mean to change those memories - as an adult. Psychologists in California and Washington were studying false memories when they stumbled on a surprisingly easy target for manipulation: foods. In a study accepted for publication in the journal Social Cognition, the researchers describe how they fooled college students into thinking that as children they had become sick when eating certain foods.

The students answered questions about their early eating memories. A week later, they were presented with a bogus food history profile that embedded a single falsehood - that they had gotten sick when eating pickles or hard-boiled eggs - among real memories.

The use of photographs by psychotherapists as memory cues for the "recovery" of patients' possible childhood sexual abuse has been called into question by a Canadian study. It found that a "staggering" two-out-of-three participants accepted a concocted false grade-school event as having really happened to them when suggestions regarding the event were supplemented with a class photo.

Christopher Diuri's temper was smoldering as he sat on the witness stand, enduring a prosecutor's withering cross-examination.

The 27-year-old mechanic's memory was challenged. His motives for coming forward as a witness were questioned. Even a past run-in with the law — a DUI arrest — was brought out.

Diuri, a plain-spoken man with a closely shaved head, finally snapped. "This case tore my whole family apart when I was a kid," he spat at Deputy Dist. Atty. Lisa Green. "And it's still doing it now."

Diuri's experience was repeated again and again last week as four former witnesses in one of the nation's biggest child molestation cases from the 1980s took the stand to say they had never been molested as children. They had only said they were, they now confessed, because law enforcement had hounded and threatened them.

The witnesses wanted to set the record straight, they said, because their false testimony had sent four innocent people to prison, including John Stoll, who is still there 19 years later. In wrenching testimony, one of the former child victims, a burly sign painter named Edward Sampley, tearfully addressed the bald, 60-year-old inmate in jailhouse brown. "I'm sorry," Sampley said, as both he and Stoll wiped away tears.

A touching scene of reconciliation? Hardly. If these young men, all in their mid-20s, thought Kern County authorities would welcome their heartfelt confessions, they were mistaken. Green hammered away at them, questioning whether they might be planning to file suit against the county and raising the prospect that they had formed some sort of conspiracy to free the very man who molested them.

You were abducted by aliens, you saw Bugs Bunny at Disneyland, and then you went up in a balloon. Didn't you? Laura Spinney on our remembrance of things past.

Alan Alda had nothing against hard-boiled eggs until last spring. Then the actor, better known as Hawkeye from M*A*S*H, paid a visit to the University of California, Irvine. In his new guise as host of a science series on American TV, he was exploring the subject of memory. The researchers showed him round, and afterwards took him for a picnic in the park. By the time he came to leave, he had developed a dislike of hard-boiled eggs based on a memory of having made himself sick on them as a child - something that never happened.

A study has revealed characteristic activity in the brain that predicts whether a memory is accurate or false. The difference occurs at the time of recall, suggesting that a test for false memory might one day be possible.

Frightening new evidence of the brain's susceptibility to suggestion was presented on Sunday to the American Association for the Advancement of Science.

Psychologists described recent experiments in which they implanted false memories, altered perceptions through subliminal messages, and demonstrated the intense emotional distress of people who believed they had been abducted by aliens.

The researchers said their work showed that courts, police and other agencies needed to be extremely wary of relying solely on the memory of witnesses - for example in sex abuse cases - because even the most intense memories could be false.

People who believe they have been abducted by aliens show some of the physiological changes associated with post-traumatic stress disorder (PTSD), US researchers have found.

The researchers at Harvard University wanted to examine the physical responses in people whom the researchers were certain harboured false memories.

Their findings show that the physical intensity of a recovered belief does not depend on whether the trauma was real or not. Intensity cannot therefore not be used to judge whether a memory was true.

Stress makes people much more likely to create false memories, say American researchers. It also appears to make them more certain that these false memories are correct.

The results could help explain why crime witnesses give conflicting evidence or pick the wrong man in a line up, the researchers say. But they do not account for "reconstructed memories" of childhood abuse.