Encyclopedia of Evolutionary Psychological Science

Living Edition
| Editors: Todd K. Shackelford, Viviana A. Weekes-Shackelford

Self-Assessment of Fighting Ability

  • Jonah HoutzEmail author
  • Melissa McDonald
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-16999-6_938-1



Males are likely to be equipped with psychological mechanisms for estimating their own fighting ability, thereby enabling them to compare their own ability to that of competitors and to opt out of interpersonal conflicts in which their likelihood of success is low.


Interpersonal conflict, particularly among males, can be quite costly in terms of risk of injury. Individuals are likely to be equipped with psychological mechanisms for self-assessment of fighting ability in order to determine whether to participate in the conflict as a function of their predicted likelihood of success. The likelihood of success is estimated by combatants through the approximations of one’s own strength relative to those with whom they are in competition. The strategies that are employed in order to gauge the fighting prowess of the self and competitors have been observed and documented by a number of studies. This entry will describe how humans, particularly males, estimate their own strength and fighting ability.

Evolutionary Foundation

Human aggression is most commonly deployed against and by males (Daly and Wilson 1983). In this way, humans conform to a widespread mammalian pattern in which the sex that invests less in offspring competes more aggressively for access to mates and the resources used to keep and acquire them (Daly and Wilson 1983). This prediction is borne out of parental investment theory (Trivers 1972). Parental investment refers to any expenditure by the parents that is meant to aid the offspring at the cost of the parents’ own potential reproductive opportunity. Given the inherent time and energetic costs of reproduction undertaken by females during the gestational and postnatal periods, large constraints are placed on females’ reproductive capacity. This shifts women’s mating strategy to one that prioritizes long-term mating and investment, rather than short-term. Conversely, males’ obligatory investment in offspring is fulfilled at the time of conception, thereby creating a reproductive ceiling that is limited only by their ability to access mating opportunities. This shifts men’s mating strategy to one that prioritizes short-term mating with minimal investment in each offspring.

This dimorphism between the sexes is the precursor to sexual selection. Females, being the primary investors in offspring, are discriminating in their mate selection, thereby evoking intrasexual competition among men who seek to gain reproductive access to many females. This competition creates large variability in the reproductive success among men, such that a few men may monopolize many females, leaving other men with few to no mating opportunities. The potential for reproductive oblivion escalates the intensity of intrasexual competition among men, often turning the competition into violent conflict. Such mating contests present the potential for a highly valued benefit, but also carry very real costs in the form of the risk of injury or death.

Minimizing Costs of Competition

The risk entailed in violent conflict is amplified when males compete with men to whom they are vastly outmatched. Even among the most formidable men, there are costs of suffering physical injury which can impair their ability to fend off future attacks, hunt, build shelters, etc. Moreover, any interpersonal conflict carries opportunity costs, in that individuals who are spending time fighting or healing from injury are not using that time to promote their fitness through other activities. It would have therefore behooved males to be able to accurately estimate their probability of winning such a contest. Lower probabilities of winning may be tolerated by men who are most in danger of reproductive failure. This is consistent with data presented by Daly and Wilson (1985) showing that rates of male–male homicide are particularly elevated among men who are unmarried and/or unemployed. Men may therefore be equipped with psychological mechanisms that calculate the expected utility of engaging in an interpersonal conflict. A key element of this calculation is an estimation of the likelihood of winning the contest which requires the ability to compare one’s own fighting ability to that of a competitor.

Perceived fighting ability is used as a gauge in order to determine the likelihood of emerging victorious in a potential fight. As males are the primary combatants in physical confrontations, it logically follows that they would have adapted methods for estimating the formidability of their competitors in relation to their own in order to properly gauge risks and rewards of confrontation.

Due to the nature of prediction, there is a trade-off between the accuracy and cost of the assessment. For example, one can estimate fighting ability very well by fighting someone to the death, but that comes at a great price. On the other side of the trade-off are perceptual estimates of fighting ability that are energetically cheap and do not risk injury but provide less precise assessments. Although not perfect, research suggests that these assessments are valid indicators of fighting ability (Sell 2016) and may therefore serve as a primary source of information in the decision of whether or not to engage in a physical contest.

Characteristics of Rival Assessment

Information about the physical capabilities of an adversary is useful in that it can inform one’s self-assessment of fighting ability. An essential aspect of self-assessment lies in rival-assessment. For example, early in childhood, young boys engage in a great deal of rough-and-tumble play (Daly 1994) that establishes a status hierarchy among boys and provides each individual with information about how their own fighting prowess compares to that of their peers. This hierarchy persists into adolescence and adulthood, changing as members become more or less formidable. Research suggests that the reason for this could be that this preference helped ancient hominids to estimate the costs, rewards, and outcome potentials of ingroup and outgroup aggressive conflicts.

A number of cues are perceived that can aid in the assessment of physical prowess. These cues are read as indicators of formidability of an opponent with regard to potential future altercations. Most definitive among perceived cues are those that provide information about an individual’s upper body strength. This is because upper body strength is the single best predictor of someone’s fighting prowess. Most human fighting requires several techniques for hitting or grappling, all of which rely primarily upon upper body strength. Upper body strength can be inferred from a number of traits that provide cues to observers to help them approximate the strength of a rival. For example, facial features predict a quarter of the variance in upper body strength, particularly among male raters, when rating male targets (Sell 2016). The structure of the face has been formed through evolutionary processes and carries with it indicators of upper body strength. These facial clues include roundness of the face, eyebrow width, and the prominence of the jaw (Windhager et al. 2011). Another cue that is predictive of upper body strength is the acoustics of the voice. According to Sell et al. (2010) listeners consistently attribute higher estimates of size and strength to men with lower pitched voices. Despite this, the pitch of a person’s voice is very limited in its predictive capability. It is thought that the vocal pitch is influenced by the vocal folds that are highly reactive to testosterone and therefore highly sexually dimorphic, which leads people to infer that more dramatically dimorphic voices must also be physically dimorphic and stronger.

Characteristics of Self-Assessment

Research investigating the mechanisms that make self-assessment of fighting ability possible is still in early stages. However, high correlations between self-assessments and objective measures of strength have shown that humans can store and update a representation of their own formidability (Sell et al. 2009). This representation is updated whenever new experience or knowledge is gained pertaining to one’s prowess. A lost fight, for example, can lead to a more modest estimate of one’s prowess. It is this estimate, the estimate of one’s own fighting ability, which allows costs and benefits to be compared through a visual assessment of a rival. Because men are significantly more likely than women to assess their own fighting ability without provocation (Buss 2016), it is inferred that they maintain a hierarchy and acknowledge their place within it. These unprovoked assessments are common because men are regularly updating their hierarchical positioning. Cues that are observed to assess the formidability of an opponent presumably could play a role in the self-assessment of formidability. However, such cues would not have been as readily accessible to ancestral humans, owing to a lack of modern technology (e.g., mirrors for self-reflection). Thus, cues to their own upper body strength would need to be indirectly inferred.

Evidence of self-assessment must be inferred through observation of conflict and pre-conflict behaviors. Males will attempt to appear larger than they are when facing rivals in order to intimidate them. When a competitor knows that they are outmatched by a rival, they will back down rather than escalating conflict. Nonhuman animals have been observed engaging in “conflicts of assessment” (Huntingford and Turner 1987; Alcock 2005) that allow the animals to ritually size up their competition before engaging in physical confrontation. This leads to a reduced chance of injury for both parties. Other animals have also been observed to win perceived contests with dummy rivals and thus perceived themselves as more capable. This led to them being more likely to challenge a real rival in future confrontations (Sell 2016). What this tells us is that animals are not only estimating their own prowess, but they can also update these estimates as they gather more information and experience much the same way that humans do.

This sizing up has also been observed to allow individuals to assert their fighting prowess and avoid conflict by driving a foe to submission before any escalation of conflict. For example, red deer have been observed to employ roaring contests before engaging in conflict (Clutton-Brock et al. 1979). These rituals provide an extra gauge for the rivals to finalize their assessment of each other in reference to their own self-assessments and make a final determination regarding the risk and rewards of contest.


Homo sapiens have adapted numerous ways of determining the likely outcome of confrontation before ever engaging in said confrontation. This ability is greatly beneficial, as it allows them to estimate both the risks of confrontation as well as the likelihood of gaining access to potential benefits (i.e., resources, access to mates, etc.). This is particularly prominent among males as they are known to be the primary instigators of conflict as they engage in competition for resources. Knowing this, it can be extrapolated that males in particular have adaptations for assessing their own fighting ability and updating this assessment as new information and experience are introduced. Further research will most likely be directed at estimating aggression based on perceptions of the physical characteristics of the self and rival alike.



  1. Alcock, J. (2005). Animal behavior: an evolutionary approach. Sunderland, MA: Sinauer Associates.Google Scholar
  2. Buss, D. M. (2016). Evolutionary psychology: The new science of the mind (5th ed.). New York: Routledge.Google Scholar
  3. Clutton-Brock, T. H., et al. (1979). The logical stag: Adaptive aspects of fighting in red deer (Cervus Elaphus L.) Animal Behaviour, 27, 211–225.  https://doi.org/10.1016/0003-3472(79)90141-6.CrossRefGoogle Scholar
  4. Daly, M., & Wilson, M. I. (1994). Evolutionary psychology of male violence. In J. Archer (Ed.), Male violence (pp. 253–288). London: Routledge.Google Scholar
  5. Daly, M., & Wilson, M. (1983). Sex, evolution, and behaviour (2nd ed.). Belmont: Wadsworth Publishing Company.Google Scholar
  6. Daly, M., & Wilson, M. (1985). Competitiveness, risk taking, and violence: the young male syndrome. Ethology and Sociobiology, 6(1), 59–73.  https://doi.org/10.1016/0162-3095(85)90041-x
  7. Huntingford, F. A., & Turner, A. K. (1987). Animal conflict. London: Chapman and Hall.Google Scholar
  8. Sell, A., Bryant, G. A., Cosmides, L., Tooby, J., Sznycer, D., Von Rueden, C., Krauss, A., & Gurven, M. (2010). Adaptations in humans for assessing physical strength from the voice. Proceedings of the Royal Society of London B: Biological Sciences, 277(1699), 3509–3518.CrossRefGoogle Scholar
  9. Sell, A., Cosmides, L., Tooby, J., Sznycer, D., von Rueden, C., & Gurven, M. (2009). Human adaptations for the visual assessment of strength and fighting ability from the body and face. Proceedings of the Royal Society of London B: Biological Sciences, 276(1656), 575–584.CrossRefGoogle Scholar
  10. Sell, A. (2016). In T. K. Shackelford (Ed.), Encyclopedia of evolutionary psychological science. Switzerland: Springer. www.springer.com/us/book/9783319196497.Google Scholar
  11. Trivers, R. (1972). Parental investment and sexual selection. Cambridge, MA: Biological Laboratories, Harvard University.Google Scholar
  12. Windhager, S., Schaefer, K., & Fink, B. (2011). Geometric morphometrics of male facial shape in relation to physical strength and perceived attractiveness, dominance, and masculinity. American Journal of Human Biology, 23(6), 805–814.CrossRefPubMedGoogle Scholar

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© Springer International Publishing AG 2018

Authors and Affiliations

  1. 1.Oakland UniversityRochesterUSA

Section editors and affiliations

  • Melissa M. McDonald
    • 1
  1. 1.Oakland UniversityRochesterUSA