It showed many people use computers instead of memorising information.
Many adults who could still recall their phone numbers from childhood could not remember their current work number or numbers of family members.
Maria Wimber from the University of Birmingham said the trend of looking up information "prevents the build-up of long-term memories".
The study, examining the memory habits of 6,000 adults in the UK, France, Germany, Italy, Spain, Belgium, the Netherlands and Luxembourg, found more than a third would turn first to computers to recall information.
The UK had the highest level, with more than half "searching online for the answer first".
But the survey suggests relying on a computer in this way has a long-term impact on the development of memories, because such push-button information can often be immediately forgotten.
"Our brain appears to strengthen a memory each time we recall it, and at the same time forget irrelevant memories that are distracting us," said Dr Wimber.
She says that the process of recalling information is a "very efficient way to create a permanent memory".
"In contrast, passively repeating information, such as repeatedly looking it up on the internet, does not create a solid, lasting memory trace in the same way."
Among adults surveyed in the UK, 45% could recall their home phone number from the age of 10, while 29% could remember their own children's phone numbers and 43% could remember their work number.
The ability to remember a partner's number was lower in the UK than anywhere else in the European survey. There were 51% in the UK who knew their partner's phone number, compared with almost 80% in Italy.
The study from Kaspersky Lab, a cybersecurity firm, says that people have become accustomed to using computer devices as an "extension" of their own brain.
It describes the rise of what it calls "digital amnesia", in which people are ready to forget important information in the belief that it can be immediately retrieved from a digital device.
The study highlights how, as well as storing factual information, there is a trend to keep personal memories in digital form. Photographs of important moments might only exist on a smartphone, with the risk of their loss if the device is lost or stolen.
"There also seems to be a risk that the constant recording of information on digital devices makes us less likely to commit this information to long-term memory, and might even distract us from properly encoding an event as it happens," said Dr Wimber.

M&S ended 4.4% higher after like-for-like general merchandising sales rose 0.7% in the three months to March 30.
Bottling company Coca Cola HBC topped the risers, closing up 4.6%.
The benchmark FTSE 100 closed up almost 24 points, or 0.35%, at 6,833.46.
M&S saw overall sales rise by 1.9% over the quarter, with like-for-like food sales also up 0.7%. Online sales jumped nearly 14%, returning M&S.com to growth.
The biggest blue-chip faller was BHP Biliton, shedding 2.6%, while fellow miners Antofagasta and Anglo American also slipped 2.1% and 1.9% respectively.
Outside the main index, drug company BTG finished up 4.8% after raising its annual revenue forecast, while Telecom Plus was the top riser on the FTSE 250, adding 4.9%.
Electrocomponents shed almost 3.6%, leaving it as the biggest faller on the 250.
On the currency markets, the pound was down slightly against the dollar at $1.4844, while against the euro, it was down almost 1% at â‚¬1.3655.

Stephen Evans, 18, from Holywell, appeared before Flintshire magistrates on Monday.
It is alleged he intended to put life in danger, or was reckless as to whether life would be endangered, amid allegations the cars were close to people's homes.
He was remanded in custody.
Magistrates said the case should be sent to Mold Crown Court where he will appear at a preliminary hearing on Friday 11 September.
An over-reliance on using computers and search engines is weakening people's memories, according to a study.
[NEXT_CONCEPT]
(Close): Marks & Spencer was among the biggest risers on the FTSE 100 on the last day of trading before the Easter break after the retailer announced a rise in non-food sales for the first time in almost four years.
[NEXT_CONCEPT]
A man has been charged with 12 counts of arson after a dozen vehicles were allegedly torched in Holywell, Flintshire.