A Special Interest Group is a non-profit, and usually voluntary, organization whose members have a common cause for which they seek to influence public policy, without seeking political control. Their primary activities are lobbying the members of legislative bodies through contribution to political parties, working to elect sympathetic or pliable politicians, and conducting covert or open propaganda campaigns. The major types of interest groups are (1) Economic association, such as chambers of commerce, trade unions, religious bodies, (2) Professional association, such as that of architects, doctors, lawyers, (3) Public interest group (PIG), such as 'Friends Of Environment' who aim to benefit people beyond their membership, and (4) Special interest group (SIG), a subgroup formed within the framework of a larger or main group to focus on a very narrow area of interest. Whereas pressure groups try to promote a cause (change the status quo), interest groups try to defend it (maintain the status quo). 

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