Differences are central to all systems approaches. The differences of interest here stem from comparisons among the variable components of a system and may be extrapolated to differences among similar components elsewhere. For example, analysts may examine differences in the message content generated by two kinds of communicators or differences within one source in different social situations, when the source is addressing different audiences, or when the source is operating with different expectations or with different information. Differ
ences in the news coverage of political campaigns have been correlated with editorial endorsements (Klein & Maccoby, 1 954) . Differences in the news cov
erage of civil rights issues have been explained in terms of various newspaper characteristics, such as geographic location, ownership, and political orientation (Broom & Reece, 1 955). Differences in newspaper content have been correlated with whether or not newspapers face competition within their regions (Nixon &
Jones, 1956).
Gerbner (1 964) demonstrated how different ideological and class orientations are reproduced in the stream of French news media messages in the reporting of an apolitical crime. Researchers have also shown how messages from one source covary with the audiences they are intended to address by comparing, for example, the political speeches that John Foster Dulles made before different kinds of groups (Cohen, 1957; Holsti, 1 962). Research has linked differences in television sports reporting of men's and women's athletics to prevailing cultural values (Tuggle,
52
CONCEPTUALI ZI N G CONTENT ANALYSIS1997) and has shown differences in works of fiction written for upper-, middle-, and lower-class readers (Albrecht, 1 956) as well as in advertisements in magazines with predominantly black and predominantly white readerships (Berkman, 1963).
Studies of differences between input and output in communication are exemplified by Allport and Faden's ( 1 940) examination of the relationship between the number of sources of information available to a newspaper and what finally appears in print, by Asheim's ( 1 950) analysis of what happens to a book when it is adapted into a movie script, and by studies that compare scientific findings with the infor
mation on such findings disseminated in the popular media.
The Hoover Institution's study titled Revolution and the Development of International Relations (RADIR) combined the analysis of differences between media and the analysis of trends. The RADIR researchers identified so-called key symbols such as democracy, equality, rights, and freedom in 1 9,553 editorials that appeared in American, British, French, German, and Russian prestige news
papers during the period 1 890-1 949. Analyses of these data led Pool ( 1 95 1 ) to correlations that he felt able to generalize. He observed, for example, that prole
tarian doctrines replace liberal traditions, that an increasing threat of war is correlated with growth in militarism and nationalism, and that hostility toward other nations is related to perceived insecurity. Although these symbols refer to aspects of a political reality, and the researchers were no doubt keenly aware of the contexts from which they were taken, the researchers did not need these references to conduct their analyses. The analysts tried to establish which differ
ences were maintained over time, which differences increased or decreased rela
tive to each other, and how they compensated for or amplified each other. For example, Pool ( 1 952b) observed that symbols of democracy become less frequent when a representative form of government is accepted rather than in dispute.
It should be noted that the knowledge of whether a government is generally accepted or in dispute comes from outside the system of selected symbols the RADIR researchers were studying. To the extent that external variables explain a system's behavior, in the form of the contributing conditions illustrated in Figure 2 . 1 , the system is not entirely autonomous. However, nobody can prevent content analysts who study such systems from including symbols of dissent, defiance, and struggle to render the systems self-explanatory.
In a very different approach, Gerbner and his colleagues accumulated a very large database on television violence in fictional programming that enabled them to make extrapolations (recommendations) of interest to policy makers ( see, e.g., Gerbner, Gross, Morgan, & Signorielli, 1 994; Gerbner, Gross, Signorielli, &
Jackson-Beeck, 1979 ) . Gerbner's ( 1 969) "message systems analysis" proposes to trace the movement of mass-media culture through time by means of a system consisting of four kinds of measures of any category of content (component) :
• The frequencies with which a system's components occur, or "what is "
• The order of priorities assigned to those components, or "what is important"
• The affective qualities associated with the components, or "what is right"
• The proximal or logical associations between particular components, or
"what is related to what"
One might question Gerbner's equation of frequencies with "what is," how sta
ble these quantitative measures really are, and whether the system is sufficiently autonomous. The point, however, is that any system of measurements, when observed long enough, will allow analysts to make predictions in the system's own terms, whatever they mean.
Simonton ( 1 994) has made an interesting and rather unusual use of the con
tent analysis of systems of differences in his analysis of musical transitions in melodies. He analyzed 15,618 melodic themes in the works of 479 classical composers working in different time periods. Simonton was interested in the relationship between originality and success, and he inferred originality from the unusualness of the transitions in particular works and for particular composers relative to the pool of all melodic themes. For example, he found that Haydn's Symphony no. 94 employs transitions found in 4% of the theme inventory, whereas Mozart's "Introduction to the Dissonant Quartet" uses transitions that occur in less than 1 % of this inventory.
Unfortunately, most practical uses of systems notions in content analysis are marred by simplistic formulations. Systems of verbal corp uses tend to require far more complex analytical constructions than simple sets of variables such as those most researchers take as the starting points of their analyses. Studies of trends, the most typical extrapolations, often focus on just one variable at a time, which denies analysts the opportunity of tracing the interactions among several variables longitudinally. The patterns that are studied often concern only one kind of rela
tionship, such as word associations. This generates graphically neat patterns, but at the expense of the ability to relate these to different kinds of patterns that might be operating simultaneously. For example, it is not too difficult to graph networks from multiple reports on "who talks to whom about what" within an organiza
tion. Such networks are made of simple binary relationships and are unable to represent more complex patterns of friendship, power, age, or goal-oriented col
laborations in terms of which individuals may well think when talking with each other. Organizational communication researchers hope that, given a sufficient amollnt of text from what transpired within an organization, they will be able to understand or predict the workings of that organization. However, extrapolating social systems into the future presents seemingly insurmountable challenges.
One problem is the sheer volume of data that researchers would need to iden
tify sufficiently invariant transformations. For this reason, most content analyses involving patterns tend to be qualitative and based on small data sets. As larger volumes of text are becoming available in electronic form, the slow development of theories and algorithms for handling large bodies of text as systems is emerg
ing as the bottleneck of content analysis. It is unlikely that the needed theories and algorithms are derivable from Newtonian mechanics or from biological sys
tems notions; rather, they must reflect the richly interactive and ecological nature of textual dynamics (Krippendorff, 1 999).