More than 1,000 students took part in a range of experiments aimed at gauging the psycholgocal impact of searching on the internet.

In one test, the internet group were given a website link which gave the answer to the question ‘how does a zip work’ while a control group were given a print-out of the same information.

When they two groups were quizzed later on an unrelated question – ‘why are cloudy nights warmer?’ the group who had searched online believed they were more knowledgeable even though they were not allowed to look up the correct answer.

Psychology professor Frank Keil, of Yale University, said the study showed that the cognitive effects of "being in search mode" on the internet were so powerful that people still feel smarter even when their online searches did not help.

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And the growing use of smartphones may exacerbate the problem because an internet search is always within reach.

“With the internet, the lines become blurry between what you know and what you think you know,” added Mr Fisher.

The researchers also believe that an inflated sense of personal knowledge also could be dangerous in the political realm or other areas involving high-stakes decisions.

"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," Mr Fisher added.

"The Internet is an enormous benefit in countless ways, but there may be some trade-offs 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."

The study was published by the American Psychological Association. Journal of Experimental Psychology: General.