contagion within the crowd in order to have lasting effects. Psychological aspects Psychological aspects are concerned with the psychology of the crowd as a group and the psychology of those who allow their will and emotions to be informed by the crowd (both discussed more comprehensively under crowd psychology). Many studies on crowds have given insights on how crowds respond to different situations. One 2009 report highlighted many observable behaviors of crowds, including evidence that crowds are able to make united decisions regarding their direction and speed of movement, even if only a few of its members have the information required to make such decisions. The degree to which informed members can affect the crowd depends on their position within the group, with those in the crowd's core likely to have a greater influence. Generally, researchers in crowd psychology have focused on the negative aspects of crowds, but not all crowds are volatile or negative in nature. For example, in the beginning of the socialist movement crowds were asked to put on their Sunday dress and march silently down the street. A more-modern example involves the sit-ins during the Civil Rights Movement. Crowds can reflect and challenge the held ideologies of their sociocultural environment. They can also serve integrative social functions, creating temporary communities. Types of crowd There is limited research into the types of crowd and crowd membership and there is no consensus as to the classification of types of crowds. Two recent scholars, Momboisse (1967) and Berlonghi (1995) focused upon purpose of existence to differentiate among crowds. Momboisse developed a system of four types: casual, conventional, expressive, and aggressive. Berlonghi classified crowds as spectator, demonstrator, or escaping, to correlate to the purpose for gathering. Other sociologists distinguished four types of crowds: casual, conventional, expressive, and acting. Casual crowds consists of people aggregated in the same place informally such as a coffee shop. There are also conventional crowds or those that come together for a regularly scheduled event including a church service and expressive crowds that meet to partake in an emotional time together like a wedding or funeral. Lastly, there are acting crowds that join to achieve a common goal or action, which could involve participating in a protest or riot. Crowds can be active (mobs) or passive (audiences). Active crowds can be further divided into aggressive, escapist, acquisitive, or expressive mobs. Aggressive mobs, which are common in