Continuity vs. (Political) Correctness:
Animal Models and Human Aggression

D. Caroline Blanchard, Mark Hebert, and Robert J. Blanchard
D. Blanchard is Research Professor at the Pacific Biomedical Research Center and Professor of Genetics and Molecular Biology at the John A. Burns School of Medicine of the University of Hawaii. Hebert is Assistant Professor of Psychology at the University of Hawaii. R. Blanchard is Professor of Psychology and Neurosciences, University of Hawaii. With HFG support, D. Blanchard and R. Blanchard are writing a book on the biology of aggression.
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Varieties of Human Aggression

Offensive Attack | If the function of offensive aggression in animals is to obtain and hold some sequestrable resource, how does this relate to more complicated human emotions and impulses? We have argued (Blanchard and Blanchard 1984) that "anger" is the emotional response to a challenge to some resource for which the angry individual has a claim. For example, data on violence resulting from "love triangles," (Wilson and Daly, 1992) suggest that these reflect attempts to discourage challenges to the perpetrator's relationship to and control over the love-object, regardless of whether the latter, or a third-party challenger, serves as victim. Similarly, Katz's (1988) descriptions of the subjective rewards of criminal and violent behavior suggest that the "resources" gained by violence often involve status and access to particularly valued women and other status symbols rather than money or goods. For many habitually violent individuals, a challenge successfully overcome is associated with strongly positive emotions; the more able the challenger, the sweeter the victory. This analysis is couched in terms that may seem inappropriate when applied to animals, but it might be considered that for violent offenders and, for example, male rats responding to an intruding challenger, the stimuli and situations eliciting aggression, and the consequences of successful and unsuccessful aggression, are very similar.

These considerations also suggest why a "challenge" is so frequent and potent a stimulus to elicit human aggression. As Daly and Wilson (1988) have pointed out, in populations of young men (who notoriously account for a disproportionate share of crimes of violence, e.g. Blanchard and Blanchard, 1983; Campbell, 1995), failures to respond to challenge jeopardize the status of the individual in the group and limit his ability to command important resources. A simple paradigm—"challenge elicits aggressive response"—emerges as a common feature of mammals, particularly young postpubertal male mammals. The specific challenge involved is typically either to the status of the individual within the group, to his access to females or other important resources, or to both. Higher primates complicate this paradigm in that other group members may get involved, either as seconds (Pereira, 1989; Silk, 1992) or in an attempt to control and defuse the situation (Reinhardt et al., 1986). Humans have contributed the factor that challenges may be purely verbal (and often quite inventive). They have also created a very encompassing form of sequestrable resource—money. The paradigm, however, remains, and it is a mammalian pattern, not one found only in dysfunctional human social groups.

Defensive Attack | If offensive aggression has some close animal-human parallels, what about defensive attack? Although defensive attack is easy to define, it is hard to observe in people, for both ethical and practical reasons. Polarized hypothetical scenarios, however, elicit consistent differences for defensive vs. offensive attack situations. Fukunaga-Stinson (reported in Blanchard and Blanchard, 1983) asked male and female students to respond to scenarios involving either a physical threat (attack by a stranger in an isolated spot) or a resource dispute by indicating the likelihood of specific actions or feelings. With reference to emotional response, fear dominated in the former, and anger in the latter. Physical and physiological responses to the two situations also differed, with "freezing" and becoming "stiff" or showing "nervous breath" describing the fear situation, while becoming "hot" or "burning" was associated with the resource dispute situation, as were "clinching fist," "staring at," and "adrenalin surge."The first choice action for the fear situation was to leave as soon as possible, followed by (for women) looking around for something to hit the attacker with, and "hit to harm" among the first five choices for both sexes. Neither of these hitting-related choices was among those selected as likely in the resource dispute situation, although a strong desire to attack the challenger was often cited. What is important is not just that these two scenarios elicited a variety of strongly differentiated physiological responses and subjective feelings, but that they were both associated with a perceived tendency to either attack, or to want to attack, the opponent.

Play Fighting | Play fighting obviously occurs in children as well as in the young of most other mammal species. Prepubertal boys (Boulton, 1993; Honig et al., 1992; Maccoby and Jacklin, 1980), like prepubertal rats (Pellis and Pellis, 1990), participate more often in fights than do comparable females. Also as in other mammals, play fighting and serious fighting in children are different, and this difference reflects the actions involved as well as factors such as facial expression and the apparent intent of the participants (Boulton, 1991a). However, the literature does contain suggestions of potential differences between the play fighting of prepubertal children and that of rats. In rats, the animal that proves to be subordinate in adulthood initiates most of the play attacks (vide Pellis and Pellis, 1992a; Smith et al., 1996), whereas play fighting in middle school children tends to involve partners that like each other and are closely matched in strength, with both weaker and stronger children initiating bouts (Boulton, 1991a,b). Another difference is that serious fighting is common enough in prepubertal children to be of concern to parents (Boulton, 1996), whereas serious fighting is seldom observed in prepubertal rats (Smith et al., 1996). Some component of this difference may reflect specific learning: In a study of middle school English children, many of the behaviors (e.g., karate chop, back kick, scissor kick) seen in play fighting but not in serious fighting represent actions that are likely to have been learned through observation/imitation, perhaps of television programs. The latter two did not occur in play fighting among Zapotec children, who did, however, show some distinctive behaviors of their own, such as burro kick and knuckle rap (Fry, 1987), suggesting that the form of playfighting in 8-12 year olds already may have been greatly altered by culture-differentiated practices.

Predation | The view that human predation has a biological link to that of closely related mammals is supported by findings that a variety of primates predate other vertebrates, including mammals (e.g. Anderson, 1986; Kudo and Mitani, 1985). In addition, primates appear to be among the few mammals that also seek out and kill animals of species that predate them, or that serve as major competitors for prey (Hiraiwa Hasegawa et al., 1986), suggesting that primate hunting is by no means limited to animals that are to be consumed. Thus the hunting of large and dangerous animals not meant for food, a feature of virtually every society that has lived in proximity to such animals, also has a clear parallel in nonhuman mammalian behavior.

Animal and Human Aggressions: Parallel Neurobehavioral Systems?

We are suggesting that, rather than try to establish a basic parallel between animal and human "aggression," it might be advantageous to look at the concept of aggression as consisting of a number of different neurobehavioral systems, at least some of which show considerable evidence of continuity between nonhuman mammals and people.

This is not to say that everything included under the human aggression rubric will have a direct counterpart in other mammals. Obviously, the "aggressive" investor or lawyer or businessman has no direct correspondent in infrahuman mammals, but this may be because the nouns are inappropriate, not the adjective (if the noun were "politician" the phrase might have an enhanced correspondence). All of these designations reflect a common theme, of actions and attitudes that seek to expand claims to resources, rights, or influence, in a variety of relevant arenas. When particular aggression paradigms are individually examined there may be either parallels that might be overlooked when an undifferentiated "aggression" concept is employed or transformations in the organization of that specific aggression paradigm as larger-brained mammals with more complex social organizations and technical capabilities are examined. This offers the possibility of real breakthroughs in relating specific human aggression phenomena to their nonhuman mammalian parallels.

What is likely to continue to be a stumbling block is the one that has been there all along, that "aggression" is one of the most value-laden terms in any language, and probably will continue to be. Thus, while aggression can be a "good" thing in the context of pursuit of a valued goal, even here it carries the baggage of an implication of activity encroaching on the rights of others; the tendency is for the protagonist to label precisely the same actions as "defense" of the desired goal, making the other guy the aggressor. As the old saw goes, virtually every country in the world has a ministry, bureau, or department of "Defense" while not one has a bureau of "Aggression."

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