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". ...