Social Assertiveness: what does it mean?
Some people are naturally more assertive, gregarious, and active. They enjoy large groups, and are often dominant figures in their social circles. In work settings they are unafraid to push their work agendas forward ~ both in seeking budget resources and results from the people working with them. By contrast, other people are more reserved and have a few close friends rather than larger social network of acquaintances and business contacts. They are less "forward" and may be uncomfortable with people who are more aggressive.
Similarly, some organizations are more densely populated by ~ and their cultures characterized by ~ more aggressive give-and-take in daily activity, and by a high level of activity overall. These are cultures where pushing is seen as a good thing, not in order to make someone else lose but to get things done. Meetings and talking things over are not viewed as a distraction from doing work; to a large extent they are the work, and are seen in this light. The sales and trading group of an investment bank would be likely to have this kind of culture.
Other work cultures are more reserved and independent. Work is done behind closed doors ~ or at least, with some privacy and allowance for focus and concentration (picture the actuarial group in an insurance underwriting firm). Boisterousness and aggressive behavior are definitely counter to the norm in these cultures. Social and business "networking" are seen as a chore to be avoided or minimized, rather than as a fundamental ~ and fun ~ part of work.