Widespread use of internet search engines and databases such as Google and IMDb.com to find information is making people lose their memory, scientists claim.
Researchers found increasing number of users relied on their computers as a form of “external memory” as frequent use of online information libraries "wired" human brains.
The study, examining the so-called "Google effect", found people had poor recall of knowledge if they knew where answers to questions were easily found.
The scientists from Columbia University, in New York, found people were increasingly bypassing discussions with friends to use the internet as their main source of information.
Experts blamed the findings, published online in this week in the journal Science, on popular search engines such as Google, Bing, Yahoo and databases such as Wikipedia and IMDb.com, the movie information site founded in Britain.
Prof Betsy Sparrow, who led the study, said such web tools were making information easy to forget and that if people could not find answers immediately it could feel like "going through withdrawal".
We are becoming symbiotic with our computer tools, growing into interconnected systems,” said Prof Sparrow, from Columbia's psychology department.
“We have become dependent on them to the same degree we are on all the knowledge we gain from our friends and co-workers — and lose if they are out of touch.
"Human memory is adapting to new communications technology."
She added: "We're not thoughtless empty-headed people who don't have memories anymore. But we are becoming particularly adept at remembering where to go find things. And that's kind of amazing."
Roddy Roediger, a psychologist at Washington University who was also involved in the study, added: "Why remember something if I know I can look it up again? In some sense, with Google and other search engines, we can off-load some of our memory demands onto machines."
In the study, titled “Google Effects on Memory: Consequences of having information at our Fingertips,” the researchers undertook four experiments involving student volunteers.
They firstly asked 46 students from the Harvard, the Ivy League university, a series of true-false questions based on trivia such as, ”An ostrich’s eye is bigger than its brain” before showing them words in different colours.
When the words could be linked to the internet, students responded more slowly and admitted they were contemplating searching for the answers on the web.
Another 60 students were then given 40 statements to type on a computer before being told that the information would either be saved or erased.
They discovered that people who believed the data would be saved were less likely to remember.
Another experiment involved 28 undergraduates from Columbia who were asked trivia questions. They were allowed to take notes and the researchers found they too struggled to remember information that would be saved.
Finally a further 34 Columbia students remembered where they stored their information in folders on their computers better than they were able to recall the information itself.
Prof Sparrow admitted it remained unclear what the effects of being so “wired” will be on people over the coming years.
She said the Internet had replaced a person's circle of friends where people would traditionally look for information.
"(They) did not make the effort to remember when they thought they could later look up the trivia statement they had read," she said.
"It may be no more than nostalgia at this point, however, to wish we were less dependent on our gadgets.
"(It shows) we must remain plugged in to know what Google knows."
Prof Sparrow said the idea for the study came as she watched the 1944 movie "Gaslight" one night with her husband and, after wondering who the actress was who played the maid, turned to her computer and Googled it.
The maid was thescreen debut of an 18 year-old Angela Lansbury, the British actress.
