A new study shows that friends lists on social networks such as Facebook can be misleading about how many of the people are true friends. In real-life situations those people probably will not be interested or reliable in giving a helping hand.

The study was conducted by Oxford University in the United Kingdom. It included 3,375 males and females between 18 and 65 years old.  

Lead researcher Robin Dunbar is a professor of evolutionary psychology at Oxford. He wanted to learn how many social media friends could be relied on in real life.  

Dunbar's study limited the number of virtual friends to 150 people. The "Dunbar Number" claims that people cannot have over 150 friends, according to Yahoo.

The study showed that participants reported an average of 27.6 of their friends were "real" friends. However, they also claimed that only 4 friends could be relied on in real-life situations.  

People with more virtual friends could also trust the same number of people in real life. However, they used more acquaintances in their list because social networks do not include levels of friendships.

The Oxford study seems to show that face-to-face communication is important. Dunbar explains that online communication cannot solve the problem of cognitive limits of social networks.

In other words, if people want more true friends they should sometimes talk to them in person. It will make the friendship stronger.

Dunbar suggests that people should not increase their circle of friends. Instead, social networks such as Facebook actually help to prevent friendships from "decaying" as time passes, according to Newsweek.

When people do not contact their friends over time, the friendship starts to decay. Dunbar explains that social networks can help to slow down that rate, but the friendship could still die if it does not include some face-to-face interaction.

Photographer Tanja Hollander did another Facebook friend experiment between 2010 and 20105. She found and snapped a photo of all her Facebook contacts.

Hollander was invited into the homes of 95 percent of her 600 social network buddies. Nearly three-quarters of them also offered her a free meal or a place to sleep for the night.