According to S Shyam Sundar, professor at Pennsylvania State University, older adults who are motivated by social bonding and curiosity tend to use Facebook as a form of social surveillance.

 "Surveillance is the idea that you're checking out what people are up to. This is something that many older adults do. They want to see how their kids are doing and, especially, what their grand children are doing," said Sundar.

Earlier studies suggest a positive relationship between bonding and bridging social capital and Facebook use among college students. "Our study extends this finding to senior citizens," added Eun Hwa Jung, mass communication researcher at Penn State.

The researchers found that the desire to stay connected to family and keep in touch with old friends or social bonding was the best predictor of Facebook adoption and use, followed closely by the desire to find and communicate with like-minded people or social bridging. Curiosity is another motivation for senior Facebook users, Jung added.

The study, published in the journal Computers in Human Behaviour, found that senior citizens were not motivated to actively participate on Facebook when family and friends prod them to use the website. "When senior citizens respond to requests to join Facebook, that tends to be a negative predictor of use," Sundar said.