Agonistic Behavior
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Agnosia Lissauer H 1890 Ein Fall von Seelenblindheit nebst einem Beitrage zur Theorie derselben. Archi fuW r Psychiatrie und Nerenkrankherten 21: 222–70 Pulvermuller F 1999 Words in the brain’s language. Behaioral and Brain Sciences 22: 253–336 Tranel D, Damasio A R 1985 Knowledge without awareness: An autonomic index of facial recognition by prosopagnosics. Science 228: 1453–4 Tranel D, Damasio A R 1996 The agnosias and apraxias. In: Bradley W G, Daroff R B, Fenichel G M, Marsden C D (eds.) Neurology in Clinical Practice, 2nd edn. Butterworth, Stoneham, MA, pp. 119–29 Tranel D, Damasio A R, Damasio H 1988 Intact recognition of facial expression, gender, and age in patients with impaired recognition of face identity. Neurology 38: 690–6 Tranel D, Damasio H, Damasio A R 1997 A neural basis for the retrieval of conceptual knowledge. Neuropsychologia 35: 1319–27 Ungerleider L G, Mishkin M 1982 Two cortical visual systems. In: Ingle D J, Goodale M A, Mansfield R J W (eds.) Analysis of Visual Behaior. MIT Press, Cambridge, MA, pp. 549–86 Young A W, Bruce V 1991 Perceptual categories and the computation of ‘grandmother.’ European Journal of Cognitie Psychology 3: 5–49 Warrington E K, McCarthy R A 1994 Multiple meaning systems in the brain: A case for visual semantics. Neuropsychologia 32: 1465–73 Warrington E K, Shallice T 1984 Category specific semantic impairments. Brain 107: 829–53
D. Tranel and A. R. Damasio
Agonistic Behavior 1. Oeriew Aggression and violence are serious social problems, as illustrated by acts ranging from school violence to wars. From an evolutionary viewpoint, on the other hand, aggression is often described as adaptive. From a humanitarian point of view it is difficult to imagine war among humans as being adaptive. The challenge to science is to resolve these contrasting views of aggression. Although research on aggression has been extensive, it has not led to significant progress in understanding and preventing aggressive acts. It was this lack of progress which led to the introduction of the concept of agonistic behavior in the mid-twentieth century. The definition of agonistic behavior was more inclusive of behaviors often not included under the umbrella of aggression. This provided a broader context for understanding aggression in relation to other behaviors. The purpose of this article is to review the current status of aggression research as it relates to agonistic behaviors. The focus will be primarily on classifying and predicting human aggression. Lower animal 326
research will be reviewed briefly in cases where the results add to the understanding of human aggression. (The term ‘agonistic’ has been used more frequently in research with lower animals than in human research.)
1.1 Definitions and Measurements Although there are no universally accepted definitions of human aggression, it has generally been defined as behavior which results in physical or psychological harm to another person and\or in the destruction of property. It usually includes overt physical acts (e.g., fighting or breaking objects) or verbal abuse. Lower animals also engage in overt physical fighting. The counterpart of verbal abuse among lower animals is ‘aggressive displays’ in which animals vocalize and\or assume threatening postures (Kalin 1999). There are data suggesting that among lower animals size is often related to achieving dominance, and lower animals will often make themselves look larger when threatened; for example, fish will make themselves appear larger by extending their fins (Clemente and Lindsley 1967). Agonistic behavior was defined as adaptive acts which arise out of conflicts between two members of the same species (Scott 1966, 1973). As noted, agonistic behaviors were more inclusive and provided a broader context within which to classify the more traditional concepts of aggression. In addition to overt aggressive acts or threats, agonistic behaviors included passive acts of submission, flight, and playful behaviors which involve physical contact. For example, human participation in sports or playful jostling would not generally be included as a form of aggression but would be included under the agonistic umbrella. Since the introduction of the term ‘agonistic,’ the differences between agonistic and aggressive behaviors have blurred and the two labels are often used interchangeably in the literature. Its introduction did not result in more productive leads for understanding or preventing human aggression. Among humans it appears that developing techniques for killing have outstripped our knowledge of how to prevent killing. The substitution of a new term for aggression has not changed this trend. The major challenge in aggression research is to develop a model which can serve to synthesize data across a wide range of scientific disciplines (Barratt et al. 1997). Techniques range from qualitative observations of behavior in naturalistic settings to more quantitative measures of aggressive behaviors in laboratory settings. Discipline-specific language has often produced confusion when comparing the results from crossdisciplinary research. Thus, as noted the major challenge to science is to view aggression from a more neutral context: a discipline-neutral model. The focus here will be on classifying and measuring
Agonistic Behaior both aggression and risk factors for aggression under four headings: (a) behavior, (b) biology, (c) cognitive or mental processes, and (d) environment or the setting in which psychosocial development takes place and aggression is expressed. No attempt will be made here to organize these four classes of descriptors and measurements into a model, but it should be noted that attempts to do so have been documented in the literature.
2. Classifying and Measuring Human Aggression Aggression is behavior. Therefore, what is to be predicted in human aggression research are aggressive acts. These acts become the criterion measures for which risk factors or predictor measures are sought. One of the more difficult tasks in aggression research is defining these acts so they can be measured and related quantitatively to potential predictors. Unless the acts are quantitatively measured, the efficacy of various interventions for controlling aggressive acts cannot be reliably determined. The properties of human aggressive acts which can be quantified are: (a) frequency with which the acts occur; (b) intensity of the act or degree of physical or psychological harm inflicted; (c) the target of the act; (d) the stimuli within the environmental setting which trigger the act; (e) the expressive form of the act (e.g., overt physical acts vs. verbal assaults); (f ) the type of act in terms of intent. These properties of aggressive acts are often used singly or in combination as outcome or criterion measures of aggression. There are three types of aggressive acts related to intent: (a) impulsive or reactive aggression or acting without thinking; (b) premeditated, planned or proactive aggression; (c) medically related aggression or aggressive acts which are committed secondary to a medical disorder, such as a closed head injury or psychiatric disorder. Classifying aggressive acts based on intent or effect is important because different interventions are effective with each type. If aggressive acts are a sign or symptom of a medical disorder, controlling the disorder should result in control of the aggression. Impulsive aggression has been shown to be related in part to low levels of a neurotransmitter, serotonin, which helps selected neurons in the brain communicate with one another. Giving a medication which increases levels of serotonin has been shown to control impulsive aggression. Selected medications used to control seizures (anticonvulsants) have also been shown to control impulsive aggression. In contrast, premeditated aggression cannot be controlled by medication but instead responds to cognitive\behavioral therapy which is based on social learning theory. This makes sense because premeditated or proactive aggression is learned in social situations. Premeditated human aggression is often compared with subhuman aggression which is related
to protecting a territory for either food or reproductive purposes. These behaviors have in part a genetic basis which generally is learned in a social context. 2.1 Human Agonistic Behaiors Not all agonistic behaviors among humans relate to social or clinical problems. For example, human sports activities are competitive and often result in physical harm to participants. Yet these events are condoned by society. The social value of these events is often explained in terms of the evolution of agonistic behaviors among lower animals that have become part of human biological drives. It is generally agreed that most common agonistic behaviors among lower animals relate to achieving dominance, which in turn is related to protecting a territory for purposes of food or reproduction as described above. Lower animals also engage in ‘play-like’ behaviors to learn to express and experience dominance in a tolerant environment. These behaviors are apparently not intended to do harm. If one observes a litter of pups as they mature, this type of ‘play’ behavior is obvious. At the human level, play and sports provide not only adaptive and socially acceptable outlets for aggressive impulses, but also an opportunity for non-participants to identify with a ‘group,’ hopefully as a ‘winner.’ This provides a sense of belonging. 2.2 Techniques for Measuring Human Aggression As noted, one of the more difficult tasks in aggression research is quantifying the aggressive acts, especially at the human level. Opportunities to observe human aggression directly in natural settings are not common and are restricted primarily to institutions such as prisons or schools. The most common ways of measuring human aggressive acts are by structured interviews or self-report measures of aggressive acts. As emphasized earlier, aggression is behavior and should not be confused with anger or hostility, which are often precursors of aggressive acts. Self-report measures of aggression can be reliable in some instances but subjects may confuse their feelings of anger and hostility with aggression. Thus, in humanlevel research, reporters (e.g., spouse) who can observe an individual’s behavior are also often used to document the aggressive acts of subjects. In hospital settings where aggressive patients are housed, rating scales of aggressive acts have been developed for use in quantifying patients’ aggressive acts on the wards.
3. Risk Factors for Human Aggression Risk factors or predictor measures of human aggression will be discussed briefly under the four headings listed in Sect. 1.1 above. Examples will be 327
Agonistic Behaior presented in each category since lack of space precludes an indepth discussion.
tomical explanations of human aggression are limited but imaging techniques (e.g., PET scans) offer promise for the future.
3.1 Biological Predictors of Aggression 3.2 Cognitie Precursors of Aggression 3.1.1 Neurotransmitters and hormones. The biological processes of the brain are controlled and maintained in large part by biochemicals called neurotransmitters and\or hormones. One of the most commonly quoted findings in psychopharmacology is that the serotonergic system of the brain is related to impulsive aggression, as noted above. Low levels of the neurotransmitter serotonin have been shown to be related in both lower animal and human studies to impulsive aggression, but not to other forms of aggression. Serotonin is involved primarily with brain systems which regulate behavioral inhibition (Ferris and Devil 1994). Other neurotransmitters (e.g., norepinephrine) have been shown to relate to creating the drive or impulse to be aggressive. As with most scientific findings, the results often become less clear as research progresses and it has been suggested that serotonin is not an exclusive or possibly even the best neurochemical marker for impulsive aggression. It is probable that in the long run a profile of neurochemical markers will be related to impulsive aggression rather than one or two neurotransmitters. Hormones have also been related to aggression. For example, testosterone levels among males have been shown to be related to aggressive behaviors (Archer 1991). 3.1.2 Genetics. Although there is evidence of heritable aggressive behaviors in lower animals, especially mice and rats, there is no creditable evidence at this time for a genetic predisposition for aggression among humans. This is especially true for molecular genetic markers. There has been suggestive evidence in behavioral genetic studies for the inheritance of aggression, but these findings have been difficult to replicate. 3.1.3 Neuroanatomy. A number of brain areas have been related to aggression in lower animals but the relevance of these findings for understanding human aggression is limited because of differences in brain function and structure. One of the main problems in relating brain structures to aggression among humans is the hierarchical nature of the brain’s structure, involving neurons which carry information across different parts of the brain. Implying that one area of the brain is responsible for aggressive acts ignores the interdependence of brain structures. Even parts of the same brain nucleus (e.g., the amygdala) can affect aggression differently because of their relationship with different brain systems. Neuroana328
Research has shown that verbal skills including reading are related to impulsive aggression. It has been proposed that the reason for this relationship is that humans often covertly verbalize control of their behaviors. Among persons with verbal skill deficits this control would be diminished, hence they would more likely be aggressive if an impulse to aggress was present. Another important cognitive process relates to conscious feelings of anger and hostility which are precursors of aggression. Measures of these two traits are often mistakenly used as measures of aggression. These traits are best classified as biological states which can be verbalized and cognitively experienced. One ‘feels angry’ but one acts aggressively. 3.3 Enironmental Precursors of Aggression It has been demonstrated among lower animals that different rearing environments can lead to changes in biological functions which are purportedly related to aggression (Kramer and Clarke 1996). For example, not having a mother in a rearing environment at critical developmental periods can lead to decreased levels of serotonin, which as noted above has been suggested as a major biological precursor of impulsive aggression. Among humans aggression is often related to living conditions (Wilson 1975). For example, persons in lower socioeconomic neighborhoods are more likely to be involved in fights than persons in higher socioeconomic neighborhoods. Again, these are complex interactions and caution is warranted in generalizing the results as ‘causes’ of aggression. 3.4 Behaioral Precursors and Laboratory Models of Aggression As is generally true for most behaviors, one of the best predictors of aggression is a past history of aggressive acts. This is true for both impulsive and premeditated aggression. Another way of studying human aggressive behavior is to generate it in laboratory situations. An example is a computer-simulated betting procedure. Individuals sit in front of a TV screen and attempt to accumulate money by pressing a button under different conditions. They think that they are competing with someone in another room for the money but they are not. Persons with tendencies toward impulsive aggression will display aggression in this well-controlled laboratory setting. This procedure can be used
Agricultural Change Theory to test the efficacy of ‘anti-aggression’ medications or for studying the effects of alcohol and other drugs on aggressive behavior.
4. Postscript This article has focused primarily on one example of agonistic behaviors, namely aggression. The need for quantitative measures to study aggression was emphasized, as well as the problems related to predicting aggressive behaviors. It is important to realize that there are different types of aggression with different sets of precursors or risk factors for each. The greatest hindrance to advancing aggression research at this time is the lack of a discipline-neutral model which can be used to synthesize discipline-specific data in the search for precursors of aggression. See also: Aggression in Adulthood, Psychology of; Behavior Therapy: Psychiatric Aspects; Hypothalamic–Pituitary–Adrenal Axis, Psychobiology of; Neurotransmitters; Sex Hormones and their Brain Receptors
Bibliography Archer J 1991 The influence of testosterone on human aggression. British Journal of Psychology 82: 1–28 Barratt E S, Sanford M S, Kent T A, Felthous A 1997 Neuropsychological and cognitive psychophysiological substrates of impulsive aggression. Biological Psychiatry 41: 1045–61 Clemente C D, Lindsley D B 1967 Aggression and Defense: Neural Mechanisms and Social Patterns. University of California Press, Los Angeles Ferris C F, Devil Y 1994 Vasopressin and serotonin interactions in the control of agonistic behavior. Psychoneuroendocrinology 19: 593–601 Kalin N H 1999 Primate models to understand human aggression. Journal of Clinical Psychiatry 60; suppl. 15: 29–32 Kramer G W, Clarke A S 1996 Social attachment, brain function, and aggression. Annals of the New York Academy of Science 794: 121–35 Scott J P 1966 Agonistic behavior of mice and rats: A review. American Zoologist 6: 683–701 Scott J P 1973 Hostility and Aggression. In: Wolman B B (ed.) Handbook of General Psychology. Prentice-Hall, Englewood Cliffs, NJ, pp. 707–19 Wilson E O 1975 Aggression. In: Sociobiology. Belknap Press of Harvard University Press, Cambridge, MA, Chap. 11, pp. 242–55
E. S. Barratt Copyright # 2001 Elsevier Science Ltd. All rights reserved.
Agricultural Change Theory Agricultural change refers not just to the difference between the first plantings 10,000 years ago and today’s computerized, industrialized, genetically en-
gineered production systems; agricultural change occurs on a daily basis, as farmers in every country of the world make decisions about what, where, and how to cultivate. The importance of the topic goes well beyond how much food is produced, how much money is made, and how the environment is affected: agriculture is intimately linked to many institutions in every society, and to population. This article examines the most influential theories of agricultural change in general, with particular emphasis on the role of population growth.
1. Oeriew Scholarship on agricultural change has been anchored by two small books with enormous impacts, both focused on the relationship between farming and population. In 1798, British clergyman Thomas Malthus argued for an intrinsic imbalance between rates of population increase and food production, concluding that it was the fate of human numbers to be checked by ‘misery and vice’—generally in the form of starvation and war. Although intended mainly as an essay on poverty, population, and Enlightenment doctrines, An Essay on the Principle of Population (Malthus 1798) infused popular and scientific thought with a particular model of agricultural change, in which a generally inelastic agricultural sector characteristically operated at the highest level allowed by available technology. In 1965, Danish agricultural economist Ester Boserup claimed to upend this model of agriculture by arguing that, particularly in ‘primitive’ agricultural systems, farmers tended to produce well below the maximum because this allowed greater efficiency (output:input ratio). She maintained that production was intensified and additional technology adopted mainly when forced by population. Each model is quite simple—dangerously oversimplified, many would now argue—but they provide invaluable starting points from which to address the complexities of agricultural change.
2. Malthus Malthus’s famous maxim from Population was that ‘the power of population is indefinitely greater than the power in the earth to produce subsistence for man … Population, when unchecked, increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio.’ Subsequent empirical research has made this position appear dubious. He used sketchy accounts of population booms in New World colonies to show that unchecked populations double every 25 years, but such growth rates have been shown to be highly exceptional. His view of agricultural production 329
International Encyclopedia of the Social & Behavioral Sciences
ISBN: 0-08-043076-7
D. Tranel and A. R. Damasio
Agonistic Behavior 1. Oeriew Aggression and violence are serious social problems, as illustrated by acts ranging from school violence to wars. From an evolutionary viewpoint, on the other hand, aggression is often described as adaptive. From a humanitarian point of view it is difficult to imagine war among humans as being adaptive. The challenge to science is to resolve these contrasting views of aggression. Although research on aggression has been extensive, it has not led to significant progress in understanding and preventing aggressive acts. It was this lack of progress which led to the introduction of the concept of agonistic behavior in the mid-twentieth century. The definition of agonistic behavior was more inclusive of behaviors often not included under the umbrella of aggression. This provided a broader context for understanding aggression in relation to other behaviors. The purpose of this article is to review the current status of aggression research as it relates to agonistic behaviors. The focus will be primarily on classifying and predicting human aggression. Lower animal 326
research will be reviewed briefly in cases where the results add to the understanding of human aggression. (The term ‘agonistic’ has been used more frequently in research with lower animals than in human research.)
1.1 Definitions and Measurements Although there are no universally accepted definitions of human aggression, it has generally been defined as behavior which results in physical or psychological harm to another person and\or in the destruction of property. It usually includes overt physical acts (e.g., fighting or breaking objects) or verbal abuse. Lower animals also engage in overt physical fighting. The counterpart of verbal abuse among lower animals is ‘aggressive displays’ in which animals vocalize and\or assume threatening postures (Kalin 1999). There are data suggesting that among lower animals size is often related to achieving dominance, and lower animals will often make themselves look larger when threatened; for example, fish will make themselves appear larger by extending their fins (Clemente and Lindsley 1967). Agonistic behavior was defined as adaptive acts which arise out of conflicts between two members of the same species (Scott 1966, 1973). As noted, agonistic behaviors were more inclusive and provided a broader context within which to classify the more traditional concepts of aggression. In addition to overt aggressive acts or threats, agonistic behaviors included passive acts of submission, flight, and playful behaviors which involve physical contact. For example, human participation in sports or playful jostling would not generally be included as a form of aggression but would be included under the agonistic umbrella. Since the introduction of the term ‘agonistic,’ the differences between agonistic and aggressive behaviors have blurred and the two labels are often used interchangeably in the literature. Its introduction did not result in more productive leads for understanding or preventing human aggression. Among humans it appears that developing techniques for killing have outstripped our knowledge of how to prevent killing. The substitution of a new term for aggression has not changed this trend. The major challenge in aggression research is to develop a model which can serve to synthesize data across a wide range of scientific disciplines (Barratt et al. 1997). Techniques range from qualitative observations of behavior in naturalistic settings to more quantitative measures of aggressive behaviors in laboratory settings. Discipline-specific language has often produced confusion when comparing the results from crossdisciplinary research. Thus, as noted the major challenge to science is to view aggression from a more neutral context: a discipline-neutral model. The focus here will be on classifying and measuring
Agonistic Behaior both aggression and risk factors for aggression under four headings: (a) behavior, (b) biology, (c) cognitive or mental processes, and (d) environment or the setting in which psychosocial development takes place and aggression is expressed. No attempt will be made here to organize these four classes of descriptors and measurements into a model, but it should be noted that attempts to do so have been documented in the literature.
2. Classifying and Measuring Human Aggression Aggression is behavior. Therefore, what is to be predicted in human aggression research are aggressive acts. These acts become the criterion measures for which risk factors or predictor measures are sought. One of the more difficult tasks in aggression research is defining these acts so they can be measured and related quantitatively to potential predictors. Unless the acts are quantitatively measured, the efficacy of various interventions for controlling aggressive acts cannot be reliably determined. The properties of human aggressive acts which can be quantified are: (a) frequency with which the acts occur; (b) intensity of the act or degree of physical or psychological harm inflicted; (c) the target of the act; (d) the stimuli within the environmental setting which trigger the act; (e) the expressive form of the act (e.g., overt physical acts vs. verbal assaults); (f ) the type of act in terms of intent. These properties of aggressive acts are often used singly or in combination as outcome or criterion measures of aggression. There are three types of aggressive acts related to intent: (a) impulsive or reactive aggression or acting without thinking; (b) premeditated, planned or proactive aggression; (c) medically related aggression or aggressive acts which are committed secondary to a medical disorder, such as a closed head injury or psychiatric disorder. Classifying aggressive acts based on intent or effect is important because different interventions are effective with each type. If aggressive acts are a sign or symptom of a medical disorder, controlling the disorder should result in control of the aggression. Impulsive aggression has been shown to be related in part to low levels of a neurotransmitter, serotonin, which helps selected neurons in the brain communicate with one another. Giving a medication which increases levels of serotonin has been shown to control impulsive aggression. Selected medications used to control seizures (anticonvulsants) have also been shown to control impulsive aggression. In contrast, premeditated aggression cannot be controlled by medication but instead responds to cognitive\behavioral therapy which is based on social learning theory. This makes sense because premeditated or proactive aggression is learned in social situations. Premeditated human aggression is often compared with subhuman aggression which is related
to protecting a territory for either food or reproductive purposes. These behaviors have in part a genetic basis which generally is learned in a social context. 2.1 Human Agonistic Behaiors Not all agonistic behaviors among humans relate to social or clinical problems. For example, human sports activities are competitive and often result in physical harm to participants. Yet these events are condoned by society. The social value of these events is often explained in terms of the evolution of agonistic behaviors among lower animals that have become part of human biological drives. It is generally agreed that most common agonistic behaviors among lower animals relate to achieving dominance, which in turn is related to protecting a territory for purposes of food or reproduction as described above. Lower animals also engage in ‘play-like’ behaviors to learn to express and experience dominance in a tolerant environment. These behaviors are apparently not intended to do harm. If one observes a litter of pups as they mature, this type of ‘play’ behavior is obvious. At the human level, play and sports provide not only adaptive and socially acceptable outlets for aggressive impulses, but also an opportunity for non-participants to identify with a ‘group,’ hopefully as a ‘winner.’ This provides a sense of belonging. 2.2 Techniques for Measuring Human Aggression As noted, one of the more difficult tasks in aggression research is quantifying the aggressive acts, especially at the human level. Opportunities to observe human aggression directly in natural settings are not common and are restricted primarily to institutions such as prisons or schools. The most common ways of measuring human aggressive acts are by structured interviews or self-report measures of aggressive acts. As emphasized earlier, aggression is behavior and should not be confused with anger or hostility, which are often precursors of aggressive acts. Self-report measures of aggression can be reliable in some instances but subjects may confuse their feelings of anger and hostility with aggression. Thus, in humanlevel research, reporters (e.g., spouse) who can observe an individual’s behavior are also often used to document the aggressive acts of subjects. In hospital settings where aggressive patients are housed, rating scales of aggressive acts have been developed for use in quantifying patients’ aggressive acts on the wards.
3. Risk Factors for Human Aggression Risk factors or predictor measures of human aggression will be discussed briefly under the four headings listed in Sect. 1.1 above. Examples will be 327
Agonistic Behaior presented in each category since lack of space precludes an indepth discussion.
tomical explanations of human aggression are limited but imaging techniques (e.g., PET scans) offer promise for the future.
3.1 Biological Predictors of Aggression 3.2 Cognitie Precursors of Aggression 3.1.1 Neurotransmitters and hormones. The biological processes of the brain are controlled and maintained in large part by biochemicals called neurotransmitters and\or hormones. One of the most commonly quoted findings in psychopharmacology is that the serotonergic system of the brain is related to impulsive aggression, as noted above. Low levels of the neurotransmitter serotonin have been shown to be related in both lower animal and human studies to impulsive aggression, but not to other forms of aggression. Serotonin is involved primarily with brain systems which regulate behavioral inhibition (Ferris and Devil 1994). Other neurotransmitters (e.g., norepinephrine) have been shown to relate to creating the drive or impulse to be aggressive. As with most scientific findings, the results often become less clear as research progresses and it has been suggested that serotonin is not an exclusive or possibly even the best neurochemical marker for impulsive aggression. It is probable that in the long run a profile of neurochemical markers will be related to impulsive aggression rather than one or two neurotransmitters. Hormones have also been related to aggression. For example, testosterone levels among males have been shown to be related to aggressive behaviors (Archer 1991). 3.1.2 Genetics. Although there is evidence of heritable aggressive behaviors in lower animals, especially mice and rats, there is no creditable evidence at this time for a genetic predisposition for aggression among humans. This is especially true for molecular genetic markers. There has been suggestive evidence in behavioral genetic studies for the inheritance of aggression, but these findings have been difficult to replicate. 3.1.3 Neuroanatomy. A number of brain areas have been related to aggression in lower animals but the relevance of these findings for understanding human aggression is limited because of differences in brain function and structure. One of the main problems in relating brain structures to aggression among humans is the hierarchical nature of the brain’s structure, involving neurons which carry information across different parts of the brain. Implying that one area of the brain is responsible for aggressive acts ignores the interdependence of brain structures. Even parts of the same brain nucleus (e.g., the amygdala) can affect aggression differently because of their relationship with different brain systems. Neuroana328
Research has shown that verbal skills including reading are related to impulsive aggression. It has been proposed that the reason for this relationship is that humans often covertly verbalize control of their behaviors. Among persons with verbal skill deficits this control would be diminished, hence they would more likely be aggressive if an impulse to aggress was present. Another important cognitive process relates to conscious feelings of anger and hostility which are precursors of aggression. Measures of these two traits are often mistakenly used as measures of aggression. These traits are best classified as biological states which can be verbalized and cognitively experienced. One ‘feels angry’ but one acts aggressively. 3.3 Enironmental Precursors of Aggression It has been demonstrated among lower animals that different rearing environments can lead to changes in biological functions which are purportedly related to aggression (Kramer and Clarke 1996). For example, not having a mother in a rearing environment at critical developmental periods can lead to decreased levels of serotonin, which as noted above has been suggested as a major biological precursor of impulsive aggression. Among humans aggression is often related to living conditions (Wilson 1975). For example, persons in lower socioeconomic neighborhoods are more likely to be involved in fights than persons in higher socioeconomic neighborhoods. Again, these are complex interactions and caution is warranted in generalizing the results as ‘causes’ of aggression. 3.4 Behaioral Precursors and Laboratory Models of Aggression As is generally true for most behaviors, one of the best predictors of aggression is a past history of aggressive acts. This is true for both impulsive and premeditated aggression. Another way of studying human aggressive behavior is to generate it in laboratory situations. An example is a computer-simulated betting procedure. Individuals sit in front of a TV screen and attempt to accumulate money by pressing a button under different conditions. They think that they are competing with someone in another room for the money but they are not. Persons with tendencies toward impulsive aggression will display aggression in this well-controlled laboratory setting. This procedure can be used
Agricultural Change Theory to test the efficacy of ‘anti-aggression’ medications or for studying the effects of alcohol and other drugs on aggressive behavior.
4. Postscript This article has focused primarily on one example of agonistic behaviors, namely aggression. The need for quantitative measures to study aggression was emphasized, as well as the problems related to predicting aggressive behaviors. It is important to realize that there are different types of aggression with different sets of precursors or risk factors for each. The greatest hindrance to advancing aggression research at this time is the lack of a discipline-neutral model which can be used to synthesize discipline-specific data in the search for precursors of aggression. See also: Aggression in Adulthood, Psychology of; Behavior Therapy: Psychiatric Aspects; Hypothalamic–Pituitary–Adrenal Axis, Psychobiology of; Neurotransmitters; Sex Hormones and their Brain Receptors
Bibliography Archer J 1991 The influence of testosterone on human aggression. British Journal of Psychology 82: 1–28 Barratt E S, Sanford M S, Kent T A, Felthous A 1997 Neuropsychological and cognitive psychophysiological substrates of impulsive aggression. Biological Psychiatry 41: 1045–61 Clemente C D, Lindsley D B 1967 Aggression and Defense: Neural Mechanisms and Social Patterns. University of California Press, Los Angeles Ferris C F, Devil Y 1994 Vasopressin and serotonin interactions in the control of agonistic behavior. Psychoneuroendocrinology 19: 593–601 Kalin N H 1999 Primate models to understand human aggression. Journal of Clinical Psychiatry 60; suppl. 15: 29–32 Kramer G W, Clarke A S 1996 Social attachment, brain function, and aggression. Annals of the New York Academy of Science 794: 121–35 Scott J P 1966 Agonistic behavior of mice and rats: A review. American Zoologist 6: 683–701 Scott J P 1973 Hostility and Aggression. In: Wolman B B (ed.) Handbook of General Psychology. Prentice-Hall, Englewood Cliffs, NJ, pp. 707–19 Wilson E O 1975 Aggression. In: Sociobiology. Belknap Press of Harvard University Press, Cambridge, MA, Chap. 11, pp. 242–55
E. S. Barratt Copyright # 2001 Elsevier Science Ltd. All rights reserved.
Agricultural Change Theory Agricultural change refers not just to the difference between the first plantings 10,000 years ago and today’s computerized, industrialized, genetically en-
gineered production systems; agricultural change occurs on a daily basis, as farmers in every country of the world make decisions about what, where, and how to cultivate. The importance of the topic goes well beyond how much food is produced, how much money is made, and how the environment is affected: agriculture is intimately linked to many institutions in every society, and to population. This article examines the most influential theories of agricultural change in general, with particular emphasis on the role of population growth.
1. Oeriew Scholarship on agricultural change has been anchored by two small books with enormous impacts, both focused on the relationship between farming and population. In 1798, British clergyman Thomas Malthus argued for an intrinsic imbalance between rates of population increase and food production, concluding that it was the fate of human numbers to be checked by ‘misery and vice’—generally in the form of starvation and war. Although intended mainly as an essay on poverty, population, and Enlightenment doctrines, An Essay on the Principle of Population (Malthus 1798) infused popular and scientific thought with a particular model of agricultural change, in which a generally inelastic agricultural sector characteristically operated at the highest level allowed by available technology. In 1965, Danish agricultural economist Ester Boserup claimed to upend this model of agriculture by arguing that, particularly in ‘primitive’ agricultural systems, farmers tended to produce well below the maximum because this allowed greater efficiency (output:input ratio). She maintained that production was intensified and additional technology adopted mainly when forced by population. Each model is quite simple—dangerously oversimplified, many would now argue—but they provide invaluable starting points from which to address the complexities of agricultural change.
2. Malthus Malthus’s famous maxim from Population was that ‘the power of population is indefinitely greater than the power in the earth to produce subsistence for man … Population, when unchecked, increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio.’ Subsequent empirical research has made this position appear dubious. He used sketchy accounts of population booms in New World colonies to show that unchecked populations double every 25 years, but such growth rates have been shown to be highly exceptional. His view of agricultural production 329
International Encyclopedia of the Social & Behavioral Sciences
ISBN: 0-08-043076-7
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