Peter L. Hurd

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Peter L. Hurd
Residence Edmonton, Alberta, Canada
Alma mater Carleton University, Simon Fraser University, Stockholm University
Known for finger length and digit ratio, social behaviour esp. in conflict
Scientific career
Fields biology, psychology
Institutions University of Texas, University of Alberta

Peter L. Hurd is an academic specialising in biology. He is an Associate Professor aligned to the Department of Psychology's Biocognition Unit, and the University's Centre for Neuroscience at the University of Alberta. His research primarily focuses on the study of the evolution of aggressive behaviour, including investigation of aggression, communication and other social behaviour which takes place between animals with conflicting interests. Major tools for this research are mathematical modeling (principally game theory and genetic algorithms). He is also interested in how the process of sexual differentiation produces individual differences in social behaviour.

Hurd conducted a study on digit ratios suggesting a positive correlation in males between aggressive tendency and the ratio of the lengths of the ring finger to his index finger. These gathered significant media attention, being reported on the BBC,[1] in the New York Times,[2] Discover Magazine,[3] Scientific American Mind,[4] National Geographic[5] and on Jay Leno.[6]


Evolution of animal signalling[edit]

Some of Hurd's most cited papers deal with the evolution of mating displays, specifically the idea that sexually selected traits have evolved to exploit previously existing biases in the sensory, or recognition, systems of their receivers, rather than being handicapped displays[7][8] Hurd has argued against the handicap principle view of animal communication, demonstrating the evolutionary stability of conventional (non-handicap) threat displays using game theoretical models.[9][10][11] Adding empirical support to this theoretical work, Hurd has also argued that threat displays in birds,[12] and headbob displays in the lizard Anolis carolinensis[13] are conventional signals, rather than handicaps. Hurd attributes the preponderance of handicap models in biology to the use of simple signalling games which are incapable of modelling conventional signalling.[14]


Hurd has classified models of fighting behaviour into those driven by: 1) fighting ability (aka resource holding potential), 2) perceived value of winning, and 3) aggressiveness and argues that if variation in the last trait -aggressiveness- exists in a biologically meaningful way, it ought to be fixed for life at an early stage of development.[15] Many studies on both human, and non-human, animals suggest that inter-individual variation in adult aggressiveness is largely organised by prenatal exposure to androgens. Digit ratio (2D:4D, the ratio of index to ring finger length) is a widely used as a proxy measure for prenatal testosterone exposure. Hurd demonstrated that men with more feminine typical-digit ratios showed lower aggressive tendency than males with more masculine-typical digit ratios.[16]

Digit ratio[edit]

Among his other research into digit ratio, Hurd has demonstrated that, while there is no difference in digit ratio between the sexes in most laboratory mice, that pups which gested next to brothers have higher digit ratios than those whose uterine neighbours were sisters,[17][18] and that the large differences in digit ratios between populations may be explained by Allen's rule and Bergmann's rule.[19]

Academic history[edit]

Strongly influenced as a youth by the anarcho-punk movement and such influences as Jonathan Kozol and A. S. Neill's Summerhill School, Hurd was an enthusiastic member of a student run free school group while unenthusiastically attending Colonel By Secondary School.[20] He then completed a BSc at Carleton University, Canada in 1990, followed by an MSc in 1993 from Simon Fraser University. He moved to Sweden to undertake a PhD at Stockholm University (Awarded in 1997) before committing to an initial postdoctoral fellowship with Mike Ryan at the University of Texas. Hurd then became a lecturer at the University of Texas in 2000 until 2001 when he moved to the University of Alberta, Canada as an Assistant Professor. Hurd was promoted to Associate Professor in 2007.

See also[edit]


  1. ^ Article on The BBC website (Retrieved June 2007)
  2. ^ Nicholas Bakalar, "What else His Ring Finger Says" the New York Times, D6 (2005)
  3. ^ Discover magazine Article
  4. ^ Scientific American Mind article
  5. ^ Summary of National Geographic Article
  6. ^ Research Overview with Reference to Jay Leno
  7. ^ Hurd PL, Wachtmeister C-A & Enquist M, 1995. Darwin's principle of antithesis revisited: a role for perceptual biases in the evolution of intraspecific signals. Proceedings of the Royal Society of London B259: 201-205.
  8. ^ Ryan MR, Rand W, Hurd PL, Phelps SM & Rand AS, 2003. Generalization in response to allopatric mate recognition signals. American Naturalist 161: 380-394.
  9. ^ Hurd PL, 1997. Is signalling of fighting ability costlier for weaker individuals? Journal of Theoretical Biology 184: 83-88.
  10. ^ Hurd PL & Enquist M. 1998. Conventional signalling in aggressive interactions: the importance of temporal structure. Journal of Theoretical Biology 192: 197-211.
  11. ^ Enquist M, Ghirlanda S, and Hurd, PL. 1998. Discrete conventional signalling of continuously varying resource value. Animal Behaviour 56: 749--753.
  12. ^ Hurd, PL; Enquist, M. 2001. Threat display in birds. Canadian Journal of Zoology 79: 931-942.
  13. ^ Hurd PL, 2004. Conventional displays: evidence for socially mediated costs of threat displays in a lizard. Aggressive Behavior 30: 326-341.
  14. ^ Hurd PL & Enquist M. 2005. A strategic taxonomy of biological communication. Animal Behaviour 70: 1155-1170.
  15. ^ Hurd PL. 2006. Resource holding potential, subjective resource value, and game theoretical models of aggressiveness signalling. Journal of Theoretical Biology 241: 639-648.
  16. ^ Bailey AA & Hurd PL, 2005. Finger length ratio predicts physical aggression in men but not women. Biological Psychology 68: 215-222
  17. ^ Bailey AA, Wahlsten D & Hurd PL, 2005. Digit ratio (2D:4D) and behavioral differences between inbred mouse strains. Genes, Brain & Behavior 4: 318-323.
  18. ^ Hurd PL, Bailey AA, Gongal PA, Yan RH, Greer JJ & Pagliardini S. 2007. Intrauterine position effects on anogenital distance and digit ratio in male and female mice. Archives of Sexual Behavior (in press).
  19. ^ Hurd PL & van Anders SM. 2007. Latitude, digit ratios, and Allen's and Bergmann's rules: A comment on Loehlin, McFadden, Medland, and Martin (2006). Archives of Sexual Behavior 36: 139-141.
  20. ^ University of Alberta, Undergrad Psychology Association "Professor of the Month" interview,

External links[edit]