"The internet is such a powerful environment, where you can enter any question, and you basically have access to the world's knowledge at your fingertips," said lead researcher Matthew Fisher, a fourth-year doctoral candidate in psychology at Yale University.
"It becomes easier to confuse your own knowledge with this external source. When people are truly on their own, they may be wildly inaccurate about how much they know and how dependent they are on the internet," Fisher said.
Participants had an inflated sense of their own knowledge after searching the internet even when they couldn't find the information they were looking for.
After conducting internet searches, participants also believed their brains were more active than the control group did.
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The cognitive effects of "being in search mode" on the internet may be so powerful that people still feel smarter even when their online searches reveal nothing, said study co-author Frank Keil, a psychology professor at Yale.
When the internet group members were given a particular website link to answer questions, they didn't report higher levels of personal knowledge on the unrelated topics than the control group.
People must be actively engaged in research when they read a book or talk to an expert rather than searching the internet, Fisher said.
"If you don't know the answer to a question, it's very apparent to you that you don't know, and it takes time and effort to find the answer. With the internet, the lines become blurry between what you know and what you think you know," he said.
An inflated sense of personal knowledge also could be dangerous in the political realm or other areas involving high-stakes decisions, Fisher said.
"In cases where decisions have big consequences, it could be important for people to distinguish their own knowledge and not assume they know something when they actually don't," he said.
"The internet is an enormous benefit in countless ways, but there may be some tradeoffs that aren't immediately obvious and this may be one of them. Accurate personal knowledge is difficult to achieve, and the internet may be making that task even harder," Fisher added.