PART 2 OF 2THE FINDINGS CONSIDERED IN THE LIGHT OF THE POSSIBLE INTERPRETATIONS
We turn now to consideration of the research findings in the light of the various interpretations cited above; but before we actually do so, a few words of review seem in order.
We have noted that the observed correlations between violence viewing and aggressive tendencies might be manifestations of one or more of three different processes, viz. (and stated somewhat summarily),
• that aggressive tendencies lead to violence viewing;
• that violence viewing leads to aggressive tendencies;
• that both aggressive tendencies and violence viewing, as well as the relationship between them, are products of some third variable or set of variables.
Two other points which have already been made also merit brief restatement. First, we have noted that the demonstration of one of the three processes would not preclude the occurrence of the others; rather, all three could be operative among different persons, or even in the same persons at different times. Second, and perhaps most important, we have noted that the correlational data available from the several reports reviewed in this chapter are by their nature inadequate to demonstrate causality. Under these circumstances, we have said, the most that we can do is search for and evaluate such specific data, or such patterns in the data, as appear to be consonant with or supportive of one or another of the interpretations, in the full knowledge that this exercise will provide no conclusive proof that anyone of the three processes is actually in operation. We begin with data which appear to support the interpretation that violence viewing leads to aggressive tendencies.Evidence for the interpretation that violence viewing causes aggression
Findings supportive of this interpretation are reported by Lefkowitz et al. (1971) and by McLeod et al. (1971b). Two findings are consonant with the occurrence of the process, and two others identify mechanisms by which the process might plausibly occur.
Lefkowitz et al. report a correlation of .31 between a measure of exposure to television violence among Grade 3 boys and peer ratings of aggression among the same boys ten years later. This finding, in and of itself, is supportive of the interpretation that relatively high early exposure to television violence produces, in some boys, aggressive tendencies which are manifested in behavior years later. However, other findings of the same study, together with certain unresolved problems regarding the measures employed, leave the dynamic not nearly as clear as the .31 correlation coefficient suggests, and are also supportive of an interpretation which would ascribe a considerable causal role to early (Grade 3 or earlier) aggressive tendencies, however these may have been engendered.
Lefkowitz et al. collected data on the violence level of favorite television programs (hereafter "TVL") and aggression from rural New York state residents in the third grade. again in the eighth grade. and again in the "thirteenth" grade (one year after graduation from high school). Favorite programs were reported by mothers when the children were in Grade 3 and by the subjects themselves in Grades 8 and 13. The principal measure of aggression was a peer rating. containing such questions as. "Who starts a fight over nothing'?"
Lefkowitz et al. found that for boys in Grade 3 there was a modest correlation (r = .2 \) between TVL and aggressive tendencies. No such relationship was found for the same boys at Grades 8 and 13 (r's = -.10 and -.05) nor for girls at any time. However. among boys. the "time-lagged correlation" between TVL at Grade 3 and aggression at Grade 13 was .31.
Several questions exist about the data which enter into this finding. The validity of mothers' reports of children's favorite programs at Grade 3 is uncertain. and such reports are in any case clearly not comparable with the self-reports obtained in later years. Perhaps more important. the peer-rating instruments used at Grade 3 and Grade g were essentially identical. but the instrument used at Grade 13 was phrased in the past tense (e.g., "Who started fights over nothing')" "Who used to say mean things?"). and the temporal reference of the replies is thus ambiguous: the Grade 13 youth may have been referring to the behavior of their prior classmates at different times across the ten-year span.
Data obtained from the boys at Grade 8 also complicate the process, although only a relatively small group was available at the time. As will be noted in Figure 2. TVL at Grade 3 correlated with aggression ratings at Grade 8 more weakly than the two had correlated at Grade 3 (.16 as compared to .21), and TVL at Grade showed a null relationship (- .02) with aggression ratings at Grade 13. Thus, the predictive power of TVL appears to have been decaying across the span of years covered in the .31 correlation. The strongest relationships involving television were based on TVL at the earliest stage. Concurrently, however, the predictive power of aggression ratings appears to have been growing. Aggression ratings at Grade 3 correlated .48 with aggression ratings at Grade 8,and these in turn correlated .65 with aggression ratings at Grade 13. Across the entire ten-year span, aggression ratings at Grade 3 correlated .38 with aggression ratings at Grade 13. The predictive power of both TVL and aggression ratings behaves one way from Grade 3 to 8 and Grade 8 to 13, but another way across the overall ten-year span.
Examination of the bivariate distribution (scatter plot) underlying each of the correlation coefficients may help to clarify the situation.
The correlation coefficient between the index based on mother's report of program preferences when the child was about eight years old and the peer rating of past aggressive behavior when the boy was about 18 years old depends almost entirely on a small number of boys at the extreme high end of the preference scale who scored extremely high on the peer-rated measure of aggressive behavior (a measure with virtually no upper limit). Without question, these boys would justify individual case study, but there appears to be hardly any relationship elsewhere in the range.
There seems little doubt that in these data aggressiveness is a continuing trait manifested by autocorrelation over time. At the same time, there is some indication that television viewing at an early stage (not later) may also have contributed to aggressiveness among a few boys.
In short, the data from the Lefkowitz et al. study may be interpreted in terms of two quite different, but not incompatible, developmental sequences. One of these emphasizes the correlation of .31 between mothers' reports of the children's radio and television program preferences at Grade 3 and peer-rated aggression at Grade 13. The other emphasizes the predictive power of the aggression measures in five-year steps. These findings suggest the need for additional research attention to early aggressive tendencies and their early sources.
McLeod et al. (1971b) asked their Wisconsin high school subjects "how frequently they had watched each of 13 shows that were on television three or four years ago" and' constructed "an index of past violence viewing" from their replies. This measure correlated as well with current overall aggression scores as did the measure of current violence viewing.
Figure 2: Correlations observed by Lefkowitz between television violence and aggression for 211 boys over a ten-year lag Cross-lagged correlations for boys between "A preference for violent television" and "Peer-rated aggression over the five years before and after the eighth grade.
Thus, in reference to a pooled sample of junior and senior high school boys and girls. current violence viewing correlated with the overall summed score of self-reports of aggression at .30, and past violence viewing correlated at .33. Both current and past violence viewing correlated at .17 with the overall summed score of others' reports of aggression. When the pooled sample is broken down by sex and age, the relationships are less regular.
These data, as far as they go, are consonant with the interpretation that violence viewing leads to aggressive behavior, for they indicate a relationship between earlier television exposure and later aggression. However, two points must be noted. First, the "past violence viewing" measure was less refined than the current violence viewing measure, in that it involved 13 programs as compared with 65 and relied upon subjects' retrospective recall to a period three or four years ago. Second, and more important, the investigators had no opportunity to obtain a past aggression measure. Had such a measure been available, and depending on its relationship to the other measures, it might variously have strengthened the likelihood that the viewing was the causal element, weakened that likelihood, or left the question in abeyance. Lacking such a measure, we can conclude only that the data cited are consonant with the interpretation that violence viewing leads to later aggression, but are not conclusive.
Mechanisms. If the available data were to indicate clearly that violence viewing does lead to aggression, a logical next question would be, "By what mechanisms?" We may inquire whether anything in the data suggests the existence of "plausible mechanisms" through which the process could occur. It is important to keep in mind that such an inquiry, in the face of data whose causal implications are not conclusive, is an exercise in hypothesis building, rather than in hypothesis testing. Failure to find any such mechanisms would not nullify the possibility of the causal sequence occurring, but might merely indicate that the necessary mechanisms have not yet been discovered. Finding such mechanisms would in turn merely indicate means through which the causal sequence could occur.
Keeping these cautions in mind, let us consider what mechanisms might exist. Two obvious possibilities are identification and learning. If viewing violence on television did lead some youths to become more aggressive, it might do so through the viewers' identification with violent characters or through their learning of techniques of aggression or their development of attitudes more favorable to aggression.
McLeod et al. (1971 a) investigated the relationship between both of these processes and violence viewing, and between both of these processes and aggression. "Identification with violent characters" was measured by replies to questions about the one person on television the respondent "would most like to be," and about which of several actors he would most "like to see at the movies." The scale was found to relate mildly to violence viewing (correlation coefficients of .21 and .15 in two pooled samples) and to relate somewhat better to aggression (.22 and .31).
The same investigators' scale of "perceived learning of aggression," further described below, related to violence viewing (.24 and .21) and more strongly to aggression (.53 and .33).
In assessing the role which "learning of aggression" might play in a behavioral dynamic, it is of course important to know precisely what is learned. The scales used in the studies under review contain items which variously bear on at least three different types of what might loosely be called "cognitive effects." More specifically, individual items variously bear on
• acquisition of knowledge about techniques (e.g., how to hit someone);
• acquisition of knowledge of pertinent facts of life (e.g., that hitting someone is in fact one way of gaining ends);
• acquisition of values (e.g., that hitting someone is a preferred way of gaining ends).
For learning to increase the likelihood of aggressive behavior, the acquisition of knowledge about techniques and about facts of life is a necessary, but not a sufficient, condition unless values favorable to aggression were also learned or had previously been learned.
The scale of "perceived learning of aggression" employed by McLeod et al., which correlated with violence viewing .24 and .21, consists of five items which constitute a mix of all three types of cognitive effects noted above. McLeod et al. (1971a) also employed a scale called "linkage of television violence to real life," which was found to relate modestly to violence viewing (.27 and .21 in two pooled samples) and to aggression (.31 and .13), but the content of the scale is again somewhat ambiguous in reference to the type of perception or learning which it represents.
The data that deal with violence viewing in relation to evaluation of violence are not fully consistent. Dominick and Greenberg (1971) found no significant difference in "approval of aggression" between high-exposed and low-exposed subjects of either sex. McLeod et al. (1971 b) found no meaningful relationship (a correlation coefficient of .09) between current viewing of violence and "approval of aggression" within their pooled sample of junior and senior high school boys and girls in Wisconsin, but did find a relationship of .27 between past violence viewing and approval of aggression.
These data on "identification with violent characters" and on "perceived learning of aggression" (at least in other respects than evaluation of violence) are consonant with a violence viewing-to-aggression hypothesis. On the other hand, the propensity to identify with violent characters or to learn aggression can also be conceived as a preexisting psychological condition. Such a dynamic might be summarized as a propensity leading both to violence viewing and to aggression. This is in essence a "third variable" or "common origin" sequence.
We may now summarize the discussion of "plausible mechanisms." Briefly, three candidate mechanisms (identification, learning, and linkage to real life) have been identified, and' each has been found to be related -- in most instances modestly -- to both violence viewing and aggression. The evidence for the operation of one plausible mechanism, that of learning favorable evaluation of violence, appears to be weak. If a causal relationship of the viewing-leads-to-aggression type does exist, however, the remaining mechanisms might be operative. This is not to assert-that that sequence does exist, since the same mechanisms are equally consonant with a causal relationship involving an antecedent common origin of both viewing and aggression.Summary: correlational evidence for the interpretation that violence viewing leads to aggression
We may now summarize the correlational evidence for the interpretation that violence viewing leads to aggression. (In the next chapter we will bring together the correlational and experimental data.) Within the studies reviewed in this chapter, all of which present correlational data, two of the highest correlation coefficients (both at about the level of .30) involved correlations in which earlier viewing was correlated with later aggression ratings. These data are supportive of the interpretation that viewing leads to aggression, within the parameters of a relationship at the .30 level. However, certain technical questions exist regarding the adequacy of the measures. In addition (or perhaps as a result), the correlational findings are equally consonant with a common origin interpretation. in which both violence viewing and aggression are conceived to stem from an antecedent condition or set of conditions. A quest for "plausible mechanisms" by which the violence viewing-to-aggression sequence might operate provided some candidate mechanisms, but these again were equally consonant with a common origin interpretation. It should be reemphasized that both a directly causal and a "third variable" process can be operating simultaneously. It is not an either-or choice.Evidence for the common origin ("third variable") interpretation
We turn now to consideration of whether the data contain any evidence supportive of or consonant with the interpretation that some antecedent condition or set of conditions may produce both violence viewing and aggression, or may in some way explain the association noted in the correlation studies. Since such an association, though a weak one, has been found, a scientific approach requires that instead of considering the matter explained, we explore for third variables that might explain it. Some ways in which such a third variable might operate have been discussed above.
Since we are here primarily interested in "common origin" third variables, we will touch only lightly on "interaction" third variables, which serve chiefly to identify different population subgroups in which the relationship between violence viewing and aggression is variously stronger and less strong. Several such variables can be observed in the data, although their action is not always consistent across the various studies. Two examples of such inconsistently behaving interactive variables will perhaps suffice to make the point.
Socioeconomic status. Robinson and Bachman (1971) observed a modest monotonic relationship between the violence level of 19-yearold boys' favorite program s and certain indices of aggression. Controlling for "education of mother" nullified the monotonicity for some groups but not for others. On the other hand, McLeod et al. (l971a) found that controlling for socioeconomic status or for school performance did not affect the relationship between violence viewing and aggression in either their Maryland or Wisconsin mixed-sex samples.
Age and sex. Upon breaking down their samples by sex and age, McLeod et al. (1971 a) found the relationship between violence viewing and aggression to be at its lowest among junior high school boys, and generally to be as strong or stronger among girls than it was among boys. Dominick and Greenberg likewise found the relationships they tested generally higher among fourth- to sixth-grade girls than among fourth- to sixth-grade boys. Lefkowitz et al., on the other hand, found virtually no relationship between their principal exposure and aggression measures for girls in Grade 3,8, or 13, or across any of these time spans.
Sex differences, insofar as they exist, could in fact constitute a candidate common origin variable. If, for example, it were consistently found that a relationship between exposure to television violence and aggression existed for boys but not for girls, it could be plausibly hypothesized that sex role conditioning was in itself sufficient to preclude the relationship developing among girls and (by the other side of the coin) to maximize the likelihood of its development among boys. However, as we have noted, the findings of these studies in reference to sex differences are far from consistent. Clarification of these inconsistencies is obviously necessary before sex role conditioning can meaningfully be considered a plausible candidate for a common origin variable.
Other candidate common origin variables exist in the data at hand, although none can be observed to be serving such a function completely, nor even sufficiently to validate it as a definite common origin variable. We will here discuss three such variables, or types of variables: preexisting levels of aggression, subjective or personality factors, and a group of variables related to the attitudes and behavior of the respondents' families.Preexisting levels of aggression
Robinson and Bachman found that controlling for levels of aggression one year ago virtually eliminated the relationship between preference for violent programs and aggression for some 90 percent of their sample, and destroyed the monotonicity of the relationship for the remaining and most aggressive ten percent.
This finding can be interpreted as supportive of a common origin interpretation, with the third variable being the condition or conditions which produce the e(j.r1ier levels of aggression. The interpretation is weakened, however, by the lack of a parallel early program preference measure (which could strengthen or weaken the interpretation) and by the fact that the male respondents were 19 years old at the time of the survey. Both their characteristic levels of aggression and their viewing preferences may by that age, or even a year earlier, have attained sufficient stability to be beyond any further interactive effect upon each other. Indeed, the data do not rule out the possibility that one of the antecedent determinants of their aggression level may have been their program preferences at some earlier stage of development.Personality factors
The data at hand contain several discrete findings which, though not individually particularly impressive, hint at a possible personality factor. or set of factors, which deserve investigation as a possible common origin variable. Thus, as previously noted, Robinson and Bachman found that controlling for aggression level a year ago nullified a previously observed relationship between violence level of favorite programs and aggression for all but the most aggressive ten percent of their sample -- a finding which suggests the possibility of a qualitative as well as quantitative difference between the ten percent and the 90 percent. In related vein, available details regarding Lefkowitz et al. 's sample of boys suggest that the observed relationship between violence level of favorite programs and aggression may be essentially a product of a very small number of extremely aggressive boys. Again, in the same vein, McIntyre and Teevan found that only about ten percent of their sample agreed with either of two statements about their favorite program ("The main character shoves people around" and "The rough guy gets his way"). The ten percent who agreed with either statement were more aggressive than the others, perceived violence in programs where others did not perceive it, and possessed various other deviant traits. 
Possibly related to the McIntyre and Teevan finding is the statistical behavior of a variable called by McLeod et al. "perceived learning of aggression." We have already noted that this index correlates with aggression more strongly than does violence viewing and have suggested that it could serve as a "plausible mechanism" in a violence viewing-to-aggression dynamic. We have suggested also that, to the degree that selective learning is a manifestation of a psychological set, that psychological set is a candidate for a common origin variable.
Taken together, these isolated findings from several studies suggest the possible existence of a set of traits characteristic of about ten percent of youth -- or at least of boys -- which merits better definition and measurement than it has yet received, and which merits investigation to see whether it is a common source of both violence viewing and aggression.Variables relating to the family
In reference to a host of topics other than exposure to television violence and its correlates or effects, the attitudes and behaviors of young persons' parents have been found to be important, and in some instances critically determinative, influences upon the attitudes and behavior of the young persons themselves. The data at hand suggest that "family" may well also play an important role in whatever causal sequence produces an association between violence viewing and aggression. Unfortunately, however, the available data are limited in scope. In sum, they cannot be said to identify "family" as a common origin third variable; they can rather be said to suggest its candidacy for such a function and to underline the need for further investigation of the role of "family" in this process.
Dominick and Greenberg tested the relative strengths of association between aggressive attitudes and three "antecedent variables," viz., "family attitudes toward violence," "social class," and "exposure to television violence." Their scale of "family attitudes" consisted of seven questions on how children "thought their parents feel about various forms of violence." Because many of the respondents could not provide adequate answers, the group was split into two groups: those whose families were "definitely antiviolence" and those whose parents had not demonstrated disapproval.  The failure of families to demonstrate disapproval was found to be more strongly related to aggressive attitudes than was "exposure to television violence" in regard to every attitude scale employed and in regard to both boys and girls. Interpretations of this finding must be tempered by the fact that the child's perception of his family's attitude may tell us more about his attitude than theirs, and by the fact that "exposure to television violence" was found to have some independent relationship with aggressive attitudes.
Within the studies under review, virtually all other data bearing on the relationship of "family" to the association between violence viewing and aggression are found in McLeod et al. (1971a and 1971b). Neither the considerable number of pertinent variables treated by these investigators nor the extensive data thereby generated can be adequately treated within this summary report. Suffice it here to say that all of the variables were measured by indices composed of several questions, and that in reference to several such indices the replies of the youth and their parents are combined. 
Two of these variables, "parental control over television viewing" and "parental interpretation of television violence," cannot be regarded as "common origin candidates" in and of themselves, but could conceivably be manifestations of more general aspects of child rearing. furthermore, they bear directly upon violence viewing. One of these, "parental control over television viewing," was found to bear virtually no relationship to the association between violence viewing and aggression (controlling for this variable left the originally observed correlation coefficient virtually unchanged). The other variable, "parental interpretation of television violence," refers to "how often" parents "used to" indicate to their children that interpersonal violence in "western and crime shows" was unlike real life and an undesirable way of solving problems. Surprisingly, the relationship between violence viewing and aggression was found to be higher among youth whose parents relatively often engaged in such interpretation than it was among youths whose parents less often provided such interpretations. A tempting speculative explanation of this finding is that parents may be more likely to provide "interpretation" for youth who view a great deal of television violence, but the available data do not provide much evidence either for or against this supposition. 
Other aspects of parental attitudes and behavior investigated by McLeod et al. are more generic and thus are more logical candidates for common origin variables. Of these, the most fully treated are "parental affection," "parental punishment," "parental emphasis on nonaggression, "and "family communication patterns."
"Parental affection" was assessed in McLeod et al. (1971a) by respondents' replies to a single question ("How often do your parents ...show that they love you?") and in McLeod et al. (1971b) by the combined answers of respondents and mothers  to that question and two others (" ... tell you they love you" and "show their affection by hugging and kissing you"). As so measured, "parental affection" was found to be essentially unrelated to violence viewing, to aggression, or to the relationship between them. Doubts may arise about the adequacy of the measure, and further inquiry, employing a more refined measure, is obviously desirable before "parental affection" can be regarded as unrelated to the phenomenon under investigation.Parental punishment, including "restrictive punishment"
McLeod et al. employed a five-item index of parental punishment. A series of statistical operations, using their most refined measures, indicated that "parental punishment" and "violence viewing" were independently related to aggression, and at almost the same level.  Parental punishment, as thus defined and measured, therefore cannot be regarded as a strong candidate for a common origin variable.
The same investigators, however, also separated components of the five-item "punishment scale" into measures of "physical punishment," "verbal punishment," and "restrictive punishment." The latter index was found to be significantly related to both violence viewing and aggression in two pooled samples. In one sample, "restrictive punishment" proved to be more strongly related to aggression, as measured by others' reports (.4I) than was violence viewing (.17). The question thus arises whether "restrictive punishment" or some frustrating child rearing practice it manifests may be a common origin variable, but the available data unfortunately provide no basis for further inquiry.Parental emphasis on nonaggression
Under this rubric, McLeod et al. inquired into the degree to which parents discouraged their children from being "mean to other kids," fighting back in self-defensive situations, doing "the bad things people do on television," and (in reference to one sample) behaving aggressively in hypothetical situations. Although this index was found to have only a trivial and generally negative relationship to either violence viewing or aggression (Chaffee and McLeod, 1971b), it was nevertheless found to be very strongly related to the relationship between violence viewing and aggression. Thus, the investigators report that "the average correlation (between violence viewing and all measures of aggression in both of the samples) is .26 in families where little stress is placed upon nonaggression; in families where such an emphasis is found, the average correlation is only .07."  Parental emphasis on nonaggression emerged as a strong candidate for a third variable. Where such emphasis is low, the relationship between violence viewing and aggression occurs; where it is high, the relationship is markedly reduced. This finding is consonant with the earlier mentioned finding of Dominick and Greenberg, to the effect that family attitudes regarding violence are more strongly related to aggressive attitudes than is violence viewing for fourth- to sixth-grade boys and girls. Taken together, the two findings strongly underscore the need for more extensive inquiry into the role which pertinent family attitudes play in the relationship between violence viewing and aggression.Family communication patterns
For some years prior to the institution of the present research program, Chaffee, McLeod, and their colleagues had been studying various types of "habitual structure ...of parent-to-child communication" (Chaffee and McLeod, 1971b). Partly before and partly within the present program. some of these investigators have examined the relationships between these patterns and media use and between these patterns and aggression.
The array of identified patterns is too complex to describe in any detail in this summary report. Suffice it here to say that two basic dimensions were identified and respectively labeled "socio-oriented" and "concept-oriented." The "socio-oriented" dimension involves "parents urging the child to keep discussions pleasant, avoid controversy. defer to his elders, and generally maintain harmony at the expense of his own ideas and opinions" (Chaffee and McLeod, 197Ib). The "concept-oriented" dimension, in contrast, involves "encouraging the child to challenge parental beliefs, to reach his own conclusions ... (and to be aware of) contrasting views on controversial issues." The investigators found that "about equal numbers of families stress either, neither, or both of these orientations."
It seems reasonable to suggest that emphasis upon the "socio-orientation" pattern would seem likely to engender considerable frustration in the child, whereas emphasis on "concept orientation" would seem likely to minimize frustration at least as regards child-parent communication.
McLeod et al. generally found relationships between these concepts and either violence viewing or aggression to be in the direction which the frustration hypothesis would suggest. Youth living under the presumably frustrating high "socio-orientation" patterns view significantly more violence than do those living under low "socio-orientation" patterns. With respect to self-reported aggressiveness, the highest scores are found under the presumably most frustrating conditions (high socio-orientation, low concept-orientation). With respect to both self-reported and other-reported aggressiveness, lowest scores are found under the presumably least frustrating conditions (high concept-orientation, low socio-orientation) (Chaffee and McLeod, 1971b).
The crucial question-whether these family communication patterns may be common origin third variables-can be answered only by testing the relationship between violence viewing and aggression within each of the four patterns. The question remains unanswered, and parent-child communication patterns remain viable but as yet unvalidated candidates for common origin third variables.Summary: evidence for the common origin interpretation
The data in the studies here under review have been examined for evidence consonant with the interpretation that some antecedent condition or set of conditions (one or more "third variables") may produce both violence viewing and aggression, or may in some way explain the association noted between them.
Although we have been primarily interested in possible "common origin variables," we noted in passing some "interactive" third variables, which identified different population subgroups in which the relationship between violence viewing and aggression was variously stronger and weaker. The behavior of these interactive variables was found to be inconsistent across studies. Socioeconomic status, for example, was found to serve this function in one study, but not in another. Sex was found to serve such a function in at least three studies, but in diametrically opposite ways: in two studies the relationship was found to be as strong or stronger for girls than it was for boys, while in one virtually no relationship was found for girls.
Preexisting levels of aggression were found in one study (Robinson and Bachman) to operate in a manner consonant with the common origin interpretation, but unavoidable limitations of the data left in abeyance the question of whether or not they actually served such a role. Personality factors, or what might well be personality factors, were found in several studies to operate in a manner indicating the need. for further investigation, but the data at hand were again deemed inadequate either to validate or to reject the candidacy of these factors for the role of common origin variables.
A number of variables relative to parental attitudes and behavior were examined. Two of these could be regarded only as manifestations of possible common origin candidates, but they were noted because of their direct bearing on television viewing and aggression. Of these, one, "parental control over television viewing," was found to bear no relationship to the association between violence viewing and aggression (McLeod et al.); the other, "parental interpretation of television violence, "was found to be associated with high relationship between violence viewing and aggression (McLeod et al.), possibly because its occurrence might be a response to considerable such viewing on the part of young people.
Among more logical candidates for common origin variables, McLeod et al. (and for the most part only these investigators) examined a number of generic aspects of familial attitudes and behaviors. They found that "parental affection" was unrelated to violence viewing, to aggression, or to the relationship between them, but questions exist about the adequacy of this measure. "Parental punishment" was found by the same investigators to be associated with both violence viewing and aggression, but its association with aggression was found to be independent of violence viewing, rather than to be the source of violence viewing.
"Parental emphasis on nonaggression" was found by McLeod et al. to be strongly related to the association between violence viewing and aggression, to the degree that the association was greatly reduced among youth whose parents strongly emphasized nonaggression. Related and supportive data were noted by Dominick and Greenberg, who found that family attitudes toward violence were more strongly related to aggressive attitudes in preadolescents than was violence viewing. Family attitudes toward aggression and violence thus remain a viable candidate for the role of a common origin, or controlling, variable.
Parent-child communication patterns were found by McLeod et al. to be strongly related to violence viewing and to aggression. Communication patterns presumably creating frustration were found to be strongly associated with high violence viewing and high aggression, while patterns presumably minimizing such frustration were found to be associated with low violence viewing and low aggression. Because the relationship of these patterns to the association between violence viewing and aggression has not yet been adequately investigated, these patterns can at present be regarded only as promising, but not validated, candidates for common origin variable status.
Thus, several candidate common origin or explanatory variables have been identified in the data. Several have failed to operate statistically in a manner consonant with common origin interpretations. Others have not been analyzed sufficiently to permit meaningful inferences about the possibility of their serving as common origin variables. At least two, "parental emphasis on nonaggression" and "family communication patterns," have operated in manners consonant with such an interpretation, but the pertinent data are as yet too limited to validate common origin status for either one.
The common origin interpretation remains viable, however, despite the fact that these variables, as defined by the scales employed, do not completely explain or nullify the observed relationships between violence viewing and aggression. Improved measures might change the picture, and so might the combination of several of these variables into a composite index of related conditions. Finally, and probably most important, necessary limitations of the studies at hand have left largely unexamined a considerable number of variables which have been found to be important or determining influences on other behaviors and attitudes. A continued examination of possible third variables is clearly indicated. Findings both in other areas and in these studies suggest that such investigation might profitably focus on personality factors and on aspects of family and peer attitudes and behaviors which are both more inclusive and more precise than those which have thus far been employed.GENERAL SUMMARY
The research studies whose findings are reviewed in this chapter all report answers by adolescents, or in some cases by younger children, to questions presented in surveys. In general, the questions were designed to elicit data on exposure to television violence and on aggressive tendencies. The data were analyzed by the investigators to determine whether there was any relationship between such exposure and aggressive behavior.Measures
One or more measures of television behavior and one or more measures of aggression were used in every study. The measures varied considerably.
Behavior in regard to television was variously measured by time spent viewing, by preference for violent programs, and by amount of viewing of violent programs. Pertinent findings suggest that the three are not equivalent measures for characterizing exposure to television violence. Under the circumstances, and lacking definitive tests, it seems reasonable to suppose that "amount of violence viewing" is the best measure of such exposure.
The measures of aggression differed along various dimensions and along a range within each dimension. Behavior reported upon differed in degree of reprehensibility, in degree of actuality (including, for example, actually accomplished behavior and projected behavior in hypothetical situations), in source (self-reports and others' reports), and in temporal reference (current and past). Pertinent data indicate a degree of communality among these measures, coupled with considerable differences between them. It is therefore important to inquire into what measures of aggression were involved in relationships found to be weak and what measures were involved in the obviously stronger relationships.Findings
The several studies investigated the relationship between exposure to television violence and aggression. employing various measures to do so. Most of the relationships observed were positive, but most were also of low magnitude. attaining levels ranging from null relationships to .21. A few of the observed relationships, however, reached levels at or just above .30. These were the relationship between violence viewing and summary self-report aggression scores reported by McLeod et al. (.30 and .32), and the correlation of .31 reported by Lefkowitz between mothers' statements of boys' favorite programs at Grade 3 and peer-rated aggression of the boys ten years later.
On the basis of these findings, and taking into account their variety and their inconsistencies, we can tentatively conclude that there is a modest relationship between exposure to television violence and aggressive behavior or tendencies, as the latter are defined in the studies at hand. The question which must therefore be considered is what this relationship signifies. More specifically, (1) what is indicated by correlation at the .30 level, and (2) since correlation is not in itself a demonstration of causal relationship, what can be deduced from these data regarding causation?The meaning of correlation coefficients and the basis of causal inference
Because the data of this chapter consist so largely of correlation coefficients, the meaning and limitations of this type of statistic must be kept in mind. As explained more fully within the chapter, a correlation coefficient of .30 may betoken any of several types of relationship, some of which do and some of which do not involve the majority of the individuals studied. We discussed "variance accountability" in Appendix E and cautioned against common misinterpretations of this technical term. Finally, we noted that positive correlation coefficients indicate that a relationship exists, but do not indicate whether that relationship is causal. In reference to the present topic, the correlation coefficients indicate that a modest relationship exists between violence viewing and some types of aggression. This relationship could conceivably manifest any or all of at least three causal sequences:
• that violence viewing leads to aggression;
• that aggression leads to violence viewing;
• that both violence viewing and aggression are products of a third variable or set of variables.Evidence for the interpretation that violence viewing causes aggression
Within the studies reviewed in this chapter, all of which present correlational data, the two highest correlation coefficients (both at about the level of .30) involved correlations in which earlier viewing was correlated with later aggression ratings. In and of themselves, these data are supportive of the interpretation that viewing leads to aggression, within the parameters of a relationship at the .30 level; but certain technical questions exist regarding the adequacy of the measures. In addition the findings are equally consonant with a common origin interpretation in which both violence viewing and aggression are conceived to stem from an antecedent condition or set of conditions.
The data were examined for "plausible mechanisms" by which violence viewing might cause aggression, if that were in fact occurring. Three such possible mechanisms ("identification," "perceived learning of aggression," and "linkage to real life") were identified. All of these, however, are equally plausible components of a process in which some antecedent condition or conditions served as the common origin of both violence viewing and aggression.Evidence for the common origin interpretation
The data in the several studies were examined for findings supportive of the common origin interpretation.
In the course of this examination, several "third variables" were noted. While neither explaining nor accounting for the relationship between violence viewing and aggression, these variables identified subgroups of the population in which that relationship was variously weaker and stronger. However, the findings in reference to these variables were not consistent across studies: in two studies, for example, the relationship between violence viewing and aggression was found to be as strong or stronger for girls than it was for boys, while in another study virtually no relationship was found for girls.
A number of candidate common origin variables were identified: preexisting levels of aggression, underlying personality factors, and a number of aspects of parental attitudes and behavior. Data on "family" variables related to parental control of television viewing, parental interpretation of television violence, parental affection, parental punishment, parental emphasis on nonaggression, and types of parent-child communication patterns.
Of this group of candidate common origin variables, several failed to operate statistically in a manner consonant with common origin interpretations. Others have not been analyzed sufficiently to permit meaningful inferences about the possibility that they are common origin variables. At least two, "parental emphasis on nonaggression" and "family communication patterns," have operated in ways consonant with such an interpretation, but the pertinent data are as yet too limited to validate common origin status for either one.
The common origin interpretation remains viable, however, despite the fact that the candidate variables here observed, and as here measured, do not completely explain or nullify the observed relationship between violence viewing and aggression. Improved measures, including indices which represent combinations of antecedent conditions, might possibly change the picture. In addition, there is need for further and more refined investigation of the role played by personality factors and by family and peer attitudes and behaviors.Conclusion
The studies reviewed in this chapter indicate that a modest relationship exists between the viewing of violence on television and aggressive tendencies. Because all of the studies present correlational data. definitive conclusions about causal relationships cannot be drawn. The evidence reviewed here is consonant both with the interpretation that violence viewing leads to aggression to a limited degree and among a limited number of young people. and with the interpretation that both the viewing and the aggression are products of an as yet unidentified third variable. The data are also consonant with the interpretation that both these, processes occur simultaneously.
* 'Throughout this chapter. some material appears in this indented and reduced-size format. Such material documents and explains statements in normal type.
1. Controlling for agreement with either statement completely eliminated a previously observed relationship between violence level of favorite programs and "aggressive" or "serious" deviance in both the ten percent and 90 percent groups, leading the investigators to state "that the subjects' perception of violence is more closely related to deviant behavior than is the objective rating of the violence content of television shows." Precisely what psychological characteristic of the respondents' psychological makeup was tapped by these statements is unclear, and the relationship which was nullified was originally so trivial (r's = .04 and .06) as to call into question the validity of the authors' quoted statement.
2. These definitions will be found in Dominick and Greenberg (1971). Tables refer to the two groups as "low approval" and "undefined" respectively.
3. More specifically. McLeod et al. (1971a) employed a sample of Maryland youth and a sample of Wisconsin youth. McLeod et al. (1971b) dealt more fully with the same Wisconsin sample. but did not deal with the Maryland sample. The measures in McLeod et al. (1971b) are in many cases refined as compared with similarly named measures in the earlier study. These more refined measures are, where possible, used in this summary. The use of the less refined measures. when available for parallel inquiries, would in general either present a weaker case or would not appreciably change the thrust of the data.
4. "Parental interpretation of television violence" was found to be related to violence viewing at the approximate level of r = .15 in each of two pooled samples, and to be essentially unrelated to summed self- or other-reports of aggression (r's ranging from - .03 to .07).
5. Appropriate pronoun substitutions were provided for mothers, e.g., " ...tell him that you love him."
6. Violence viewing correlated .26 with aggression, with "parental punishment" and "parental affection" simultaneously partialled out. "Parental punishment" correlated .20 with aggression, with violence viewing and "parental affection" simultaneously partialled out. The partial effect of "parental affection" was negligible (McLeod et al., 1971b).
7. A decreased correlation in the presence of high parental emphasis on nonaggression, as compared to low parental emphasis on nonaggression, was furthermore observed in all but one of the eight sex-and-age subgroups, the single exception being senior high school boys in the Wisconsin sample. McLeod et al. (1971a) and McLeod et al. (1971b) confirm the direction of effect.