<P> At the University of Chicago, Robert Park and Herbert Blumer agreed with the speculations of LeBon and other that crowds are indeed emotional . But to them a crowd is capable of any emotion, not only the negative ones of anger and fear . </P> <P> A number of authors modify the common - sense notion of the crowd to include episodes during which the participants are not assembled in one place but are dispersed over a large area . Turner and Killian refer to such episodes as diffuse crowds, examples being Billy Graham's revivals, panics about sexual perils, witch hunts and Red scares . Their expanded definition of the crowd is justified if propositions which hold true among compact crowds do so for diffuse crowds as well . </P> <P> Some psychologists have claimed that there are three fundamental human emotions: fear, joy, and anger . Neil Smelser, John Lofland, and others have proposed three corresponding forms of the crowd: the panic (an expression of fear), the craze (an expression of joy), and the hostile outburst (an expression of anger). Each of the three emotions can characterize either a compact or a diffuse crowd, the result being a scheme of six types of crowds . Lofland has offered the most explicit discussion of these types . </P> <P> Boom distinguishes the crowd, which expresses a common emotion, from a public, which discusses a single issue . Thus, a public is not equivalent to all of the members of a society . Obviously, this is not the usual use of the word, "public ." To Park and Blumer, there are as many publics as there are issues . A public comes into being when discussion of an issue begins, and ceases to be when it reaches a decision on it . </P>

Who defined sociology as the science of collective behaviour