Skip to main content Accessibility help
  • Print publication year: 2016
  • Online publication date: May 2016

6 - Anxiety…from scratch: emotional response to tense situations

from Part II - How conflicts shape societies


You have probably noticed the ambiguity and vagueness in the use of the word ‘anxiety.’ Generally one means a subjective condition, caused by the perception that an ‘evolution of fear’ has been consummated. Such a condition may be called an emotion. What is an emotion in the dynamic sense? Certainly something very complex.

Sigmund Freud, 1969

Stress, anxiety and…evolution

Back in 1872, Darwin, in The Expression of the Emotions in Man and Animals, wrote about emotion expression as the possible result of ‘the direct action of the excited nervous system on the body independently of the will’. In the whole animal world, bodily movements are able to reveal and unveil emotions not apparent otherwise. In humans, gestures, facial expressions and, more in general, non-verbal behaviours are an integral part of how we express our emotions. Emotions include anxiety, which can be linked to fear, motivational conflict, or uncertainty in decision-making (Morgan, 2006).

Defining anxiety is not easy, as also recognised by Sigmund Freud back in 1920 (see the 1969 edition). Linguistically speaking, anxiety is defined as a ‘…feeling of nervousness or worry about something that is happening or might happen in the future’ or, similarly, ‘a feeling of worry, nervousness, or unease about something with an uncertain outcome’. Stress is defined, instead, as ‘great worry caused by a difficult situation, or something that causes this condition’ or ‘a state of mental or emotional strain or tension resulting from adverse or demanding circumstances’ (definitions by Cambridge and Oxford online dictionaries, respectively). From these non-technical definitions, it is possible to infer intuitively that anxiety can be related to stress but also that the difference between stress and anxiety is not clear-cut. Indeed, a plethora of models, theories and hypotheses have been put forth to integrate stress and anxiety into a single framework. However, the behavioural, physiological, psychological and clinical implications of anxiety and stress responses have proven difficult to untangle.

In Homo sapiens, non-human primates and other mammals, anxiety is an emotional state involving tension and/or agitation, with both physiological and behavioural implications (van Riezen and Segal, 1988; Craig et al., 1995; Barros and Tomas, 2002; Bourin et al., 2007). Indeed, anxiety is associated with a characteristic set of behavioural responses, including avoidance, vigilance and arousal, which evolved to protect the individual from danger (Gross and Hen, 2004).

Related content

Powered by UNSILO
Abbott, D. H., Keverne, E. B., Bercovitch, F. B., et al. (2003). Are subordinates always stressed? A comparative analysis of rank differences in cortisol levels among primates. Hormones and Behavior, 43, 67–82.
Alexander, S. L. & Irvine, C. H. G (1998). The effect of social stress on adrenal axis activity in horses: The importance of monitoring corticosteroid-binding globulin capacity. Journal of Endocrinology, 157, 425–432.
Altmann, J. (1974). Observational study of behaviour sampling methods. Behaviour, 49, 227–265.
Altmann, S. A. (1967). The structure of primate social communication. In: Altmann, S. A (ed.), Social Communication among Primates. Chicago: University of Chicago Press, pp. 325–362.
Anderson, , , J. R. & Meno, P. (2003). Psychological influences on yawning in children. Current Psychology Letters, 11, 1–7.
Anderson, J. R., Myowa-Yamakoshi, M. & Matsuzawa, T. (2004). Contagious yawning in chimpanzees. Proceedings of the Royal Society B: Biological Sciences, 271, 468–470.
Arnold, K. & Whiten, A. (2001). Post-conflict behaviour of wild chimpanzees (Pan troglodytes schweinfurthii) in the Budongo Forest, Uganda. Behaviour, 138, 649–690.
Aureli, F. (1997). Post-conflict anxiety in nonhuman primates: The mediating role of emotion in conflict resolution. Aggressive Behaviour, 23, 315–328.
Aureli, F. & de Waal, F. B. M. (1997). Inhibition of social behavior in chimpanzees under high-density conditions. American Journal of Primatology, 41, 213–228.
Aureli, F. & Schaffner, C. M. (2008). Social interactions, social relationships and the social system of spider monkeys. In: Spider Monkeys: Behavior, ecology and evolution of the genus Ateles. Cambridge University Press, pp. 236–265.
Aureli, F. & Smucny, D. A. (2000). The role of emotion in conflict and conflict resolution. In: Aureli, F. & de Waal, F. B. M. (eds), Natural Conflict Resolution. Berkeley, CA: University of California Press, pp. 199–224.
Aureli, F. & van Schaik, C. P. (1991). Post-conflict behaviour in long-tailed macaques (Macaca fascicularis): II Coping with the uncertainty. Ethology, 89, 101–114.
Aureli, F. & Whiten, A. (2003). Emotions and behavioral flexibility. In: Maestripieri, D. (ed.), Primate Psychology – The Mind and Behavior of Human and Nonhuman Primates. Cambridge, MA: Harvard University Press, pp. 289–323.
Aureli, F. & Yates, K. (2010). Distress prevention by grooming others in crested black macaques. Biology Letters, 6, 27–29.
Aureli, F., van Schaik, C. P. & van Hooff, J. A. R. A. M. (1989). Functional aspects of reconciliation among captive long-tailed macaques (Macaca fascicularis). American Journal of Primatology 19, 38–51.
Aureli, F., Preston, S. D. & de Waal, F. (1999). Heart rate responses to social interactions in free-moving rhesus macaques (Macaca mulatta): a pilot study. Journal of Comparative Psychology, 113, 59–65.
Aureli, F., Cords, M. & van Schaik, C. P. (2002). Conflict resolution following aggression in gregarious animals: a predictive framework. Animal Behaviour, 64, 325–343.
Baenninger, R. (1987). Some comparative aspects of yawning in Betta splendens, Homo sapiens, Panthera leo and Papio sphinx. Journal of Comparative Psychology, 101, 349–354.
Baenninger, R. (1997). On yawning and its functions. Psychonomic Bulletin & Review, 4, 198–207.
Baenninger, R., Binkley, S. & Baenninger, M. (1996). Field observations of yawning and activity in humans. Physiology and Behavior, 59, 421–425.
Baker, K. C. (2004). Benefits of positive human interaction for socially-housed chimpanzees. Animal Welfare (South Mimms, England), 13, 239–245.
Baker, K. C. & Aureli, F. (1997). Behavioural indicators of anxiety: an empirical test in chimpanzees. Behaviour, 134, 1031–1050.
Balm, P. H. M. (1999). Stress Physiology in Animals. Sheffield: Sheffield Academic Press.
Balon, R. (2005). Measuring anxiety: are we getting what we need?Depress Anxiety, 22, 1–10.
Barros, M. & Tomaz, C. (2002). Non-human primate models for investigating fear and anxiety. Neuroscince & Biobehavioral Reviews, 26, 187–201.
Barros, M., Boere, V., Huston, J. P. & Tomaz, C. (2000). Measuring fear and anxiety in the marmoset (Callithrix penicillata) with a novel predator confrontation model: effects of diazepam. Behavioural Brain Research, 108, 205–211.
Barton, R. A. (1987). Allogrooming as mutualism in diurnal lemurs. Primates, 28, 539–542.
Beach, F. A. & Inman, N. G. (1965). Effects of castration and androgen replacement on mating in male quail. PNAS, 54, 1426–1431.
Bertrand, M. (1969). The Behavioural Repertoire of the Stumptail Macaque. Basel: Karger.
Biben, M. & Champoux, M. (1999). Play and stress: cortisol as a negative correlate of play in Saimiri. In: Reifel, S. (ed.), Play and Cultures Study, vol. 2, 91–208.
Blaustein, J. D. (2010). Feminine reproductive behavior and physiology in rodents: integration of hormonal, behavioral, and environmental influences. In: D. W. Pfaff, et al. (eds), Hormones, Brain and Behavior, 2nd ed. New York: Academic Press, pp. 67–107.
Boccia, M. L., Reite, M. & Laudenslager, M. (1989). On the physiology of grooming in a pigtail macaque. Physiology and Behavior, 45, 667–670.
Bourin, M., Petit-Demoulière, B., Nic Dhonnchadha, B. & Hascöet, M. (2007). Animal models of anxiety in mice. Fundamental & Clinical Pharmacology, 21, 567–574.
Breen, K. M. & Karsch, F. J. (2004). Does cortisol inhibit pulsatile luteinizing hormone secretion at the hypothalamic or pituitary level?Endocrinology, 145, 692–698.
Brockman, D. K. & Whitten, P. L. (1996). Reproduction in free-ranging Propithecus verreauxi: estrus and the relationship between multiple partner matings and fertilization. American Journal of Physical Anthropology, 100, 57–96.
Brockman, D. K., Whitten, P. L., Richard, A. F. & Schneider, A. (1998). Reproduction in free-ranging male Propithecus verreauxi: The hormonal correlates of mating and aggression. American Journal of Physical Anthropology, 105, 137–151.
Brockman, D. K., Whitten, P. L., Richard, A. F. & Benander, B. (2001). Birth season testosterone levels in male Verreaux's sifaka, Propithecus verreauxi: insights into socio-demographic factors mediating seasonal testicular function. Behavioral Ecology and Sociobiology, 49, 117–127.
Brydges, N. M., Hall, L., Nicolson, R., Holmes, M. C. & Hall, J. (2012). The effects of juvenile stress on anxiety, cognitive bias and decision making in adulthood: A rat model. PLoS ONE, 7, e48143.
Campbell, M. W. & de Waal, F. B. M. (2011). Ingroup-outgroup bias in contagious yawning by chimpanzees supports link to empathy. PLoS ONE, 6(4), e18283.
Campbell, M. W., Devyn Carter, J., Proctor, D., Eisenberg, M. L. & de Waal, F. B. M. (2009). Computer animation stimulates contagious yawning in chimpanzees. Proceedings of the Royal Society B: Biological Sciences, 276, 4255–4259.
Campennì, M. & Schino, G. (2014). Partner choice promotes cooperation: The two faces of testing with agent-based models. Journal of Theoretical Biology, 344, 49–55.
Castles, D. L. & Whiten, A. (1998). Post-conflict behaviour of wild olive baboons. II. Stress and self-directed behaviour. Ethology, 104, 148–160.
Castles, D. L., Whiten, A. & Aureli, F. (1999). Social anxiety, relationships and self-directed behaviour among wild female olive baboons. Animal Behaviour, 58, 1207–1215.
Cavigelli, S. A. (1999). Behavioral patterns associated with faecal cortisol levels in free-ranging female ring-tailed lemurs, Lemur catta.Animal Behaviour, 57, 935–944.
Cavigelli, S. A., & Pereira, M. E. (2000). Mating season aggression and fecal testosterone levels in male ring-tailed lemurs (Lemur catta). Hormones and Behavior, 37, 246–255.
Cherkin, D. C., Sherman, K. J., Kahn, J., et al. (2009). Effectiveness of focused structural massage and relaxation massage for chronic low back pain: protocol for a randomized controlled trial. Trials, 10, 96.
Cilia, J. & Piper, D. C. (1997). Marmoset conspecific confrontation: an ethologically-based model of anxiety. Pharmacology Biochemistry and Behavior, 58, 85–91.
Coe, C. L., Mendoza, S. P., Smotherman, W. P. & Levine, S. (1978). Mother–infant attachment in the squirrel monkey: adrenal response to separation. Behavioral Biology, 22, 256–263.
Coles, M. E., Turk, C. L., Heimberg, R. G. & Fresco, D. M. (2001). Effects of varying levels of anxiety within social situations: Relationship to memory perspective and attributions in social phobia. Behaviour Research and Therapy, 39, 651–665.
Cordoni, G. & Palagi, E. (2007). Response of captive lowland gorillas (Gorilla gorilla gorilla) to different housing conditions: testing the aggression-density and coping models. Journal of Comparative Psychology, 121, 171–180.
Craig, K. J., Brown, K. J. & Baum, A. (1995). Environmental factors in the etiology of anxiety. In: Bloom, F. E. & Kupfer, D. J. (eds), Psychopharmacology: The fourth generation of progress. New York: Raven, pp. 1325–1339.
Daniel, J. R., Santos, A. J. & Vicente, L. (2008). Correlates of self-directed behaviours in captive Cercopithecus aethiops. International Journal of Primatology, 29, 1219–1226.
Darwin, C. (1872). The Expression of the Emotions in Man Animals. London: John Murray.
Das, M., Penke, Z., & van Hooff, J. A. R. A. M. (1998). Postconflict affiliation and stress-related behavior of long-tailed macaque aggressors. International Journal of Primatology, 19, 53–71.
Davitz, J. & Mason, D. J. (1955). Socially facilitated reduction of fear response in rats. Journal of Comparative and Physiological Psychology, 47, 941–947.
de Waal, F. B. M. (1987). Tension regulation and nonreproductive functions of sex in captive bonobos (Pan paniscus). National Geographic Research, 3, 318–335.
de Waal, F. B. M. & van Roosmaleen, A. (1979). Reconciliation and consolation among chimpanzees. Behavioral Ecology and Sociobiology, 5, 55–66.
Demuru, E. & Palagi, E. (2012). In Bonobos yawn contagion is higher among kin and friends. PLoS ONE, 7(11), e49613.
Deputte, B. L. (1994). Ethological study of yawning in primates. 1. Quantitative analysis and study of causation in two species of old world monkeys (Cercocebus albigena and Macaca fascicularis). Ethology, 98, 221–245.
Dunbar, R. I. M. (1991). Functional significance of social grooming in primates. Folia Primatologica, 57, 121–131.
Dunbar, R. I. M. & Dunbar, E. P. (1975). Social Dynamics of Gelada Baboons. Basel: Karger.
Evans, C. S. & Goy, R. W. (1968). Social behaviour and reproductive cycles in captive ring-tailed lemurs (Lemur catta). Journal of Zoology, 156, 181–197.
Evers, E., de Vries, H., Spruijt, B. M. & Sterck, E. H. M. (2014). The EMO-model: An agent-based model of primate social behavior regulated by two emotional dimensions, anxiety-FEAR and satisfaction-LIKE. PLoS ONE, 9, 2 e87955.
Fagen, R. & Fagen, J. (2004). Juvenile survival and benefits of play behaviour in brown bears, Ursus arctos. Evolutionary Ecology Research, 6, 89–102.
Fraser, O. N., Stahl, D., & Aureli, F. (2008). Stress reduction through consolation in chimpanzees. PNAS, 105, 8557–8562.
Fraser, O. N., Stahl, D. & Aureli, F. (2010). The function and determinants of reconciliation in Pan troglodytes. International Journal of Primatology, 31, 39–57.
Freud, S. (1969). A General Introduction to Psychoanalysis, revised edition. New York: Touchstone.
Fried, R. (1994). Evaluation and treatment of “psychogenic” pruritus and self-excoriation. Journal of the American Academy of Dermatology, 30, 993–999.
Gallese, V., Keysers, C. & Rizzolatti, G. (2004). A unifying view of the basis of social cognition. Trends in Cognitive Sciences, 8, 396–403.
Galloway, A. T., Addessi, E., Fragaszy, D. & Visalberghi, E. (2005). Social facilitation of eating familiar food in tufted capuchin monkeys (Cebus apella): Does it involve behavioral coordination?International Journal of Primatology, 26, 181–189.
Gallup, A. C. & Eldakar, O. T. (2013). The thermoregulatory theory of yawning: what we know from over 5 years of research. Frontiers in Neuroscience, 6, 188.
Gallup, A. C., Miller, M. L. & Clark, A. B. (2009). Yawning and thermoregulation in budgerigars (Melopsittacus undulatus). Animal Behaviour, 77, 109–113.
Geissmann, T. & Mutschler, T. (2006). Diurnal distribution of loud calls in sympatric wild indri (Indri indri) and ruffed lemurs (Varecia variegata): implications for call functions. Primates, 47, 393–396.
Genuth, S. M. (1993). The endocrine system. In: Berne, R. M. & Levy, M. N. (eds), Physiology. Vol. III. St. Louis: Mosby Yearbook, pp. 813–1024.
Giganti, F. & Zilli, I. (2011). The daily time course of contagious and spontaneous yawning among humans. Journal of Ethology, 29, 215–219.
Goodall, J. (1968). A preliminary report on the expressive movements and communication in the Gombe stream chimpanzees. In: Jay, P. C. (ed.), Primates: studies in adaptation and variability.New York: Holt, Rinehart and Winston, pp. 313–374.
Gould, L. (1994). Patterns of affiliative behavior in adult male ringtailed lemurs (Lemur catta) at the Beza-Mahafaly Reserve, Madagascar. Ph.D. Dissertation, Washington University.
Gould, L. (1997). Intermale affiliative relationships in ringtailed lemurs (Lemur catta) at the Beza-Mahafaly Reserve, Madagascar. Primates, 38, 15–30.
Gould, L. (2006). Male sociality and integration during the dispersal process in Lemur catta: a case study. In: Jolly, A., Sussman, R. W., Koyama, N. & Rasamimanana, H. (eds), Ringtailed Lemur Biology: Lemur catta in Madagascar. New York: Springer, pp. 296–310.
Gould, L, & Ziegler, T. (2007). Variation in fecal testosterone levels, inter-male aggression, dominance rank and age during mating and post-mating periods in wild adult male ring-tailed lemurs (Lemur catta). American Journal of Primatology, 69, 1325–1339.
Gould, L.Ziegler, T. & Wittwer, D. (2005). Effects of reproductive and social variables on fecal glucocorticoid levels in a sample of adult male ring-tailed lemurs (Lemur catta) at the Beza Mahafaly Reserve, Madagascar. American Journal of Primatology, 67, 5–23.
Gross, C. & Hen, R. (2004). The developmental origins of anxiety. Nature Reviews Neuroscience, 5, 545–552.
Guggisberg, A. G., Mathis, J. H., Uli, S. & Hess, C. W. (2007). The functional relationship between yawning and vigilance. Behavioural Brain Research, 179, 159–166.
Guggisberg, A. G., Mathis, J., Schnider, A. and Hess, C. W. (2010). Why do we yawn?Neuroscience & Biobehavioral Reviews, 34, 1267–1276.
Hadidian, J. (1980).Yawning in an old world monkey (Macaca nigra). Behaviour, 75, 133–147.
Hayes, J. & Cox, C. (1999). Immediate effects of a five-minute foot massage on patients in critical care. Intensive and Critical Care Nursing, 15, 77–82.
Hecht, E. E., Gutman, D. A., Preuss, T. al. (2012). Process versus product in social learning: comparative diffusion tensor imaging of neural systems for action execution-observation matching in macaques, chimpanzees, and humans. Cerebral Cortex, 23, 1014–1024.
Hellhammer, K. H., Buchtal, J., Gutberlet, I. & Kirschbaum, C. (1997). Social hierarchy and adrenocortical stress reactivity in men. Psychoneuroendocrinology, 22, 643–650.
Hennessy, M. B., Maken, D. S. & Graves, F. C. (2000). Consequences of the presence of the mother or unfamiliar adult female on cortisol, ACTH, testosterone and behavioral responses of periadolescent guinea pigs during exposure to novelty. Psychoneuroendocrinology, 25, 619–632.
Higham, J. P., MacLarnon, A. M., Heistermann, M., Ross, C. & Semple, S. (2009). Rates of self-directed behaviour and faecal glucocorticoid levels are not correlated in female wild olive baboons (Papio hamadryas anubis). Stress: the International Journal on the Biology of Stress, 12, 526–532.
Jolly, A. (1966). Lemur Behavior: a Madagascar field study. Chicago:University of Chicago Press.
Jolly, A., Rasamimanana, H. R., Kinnaird, M. F., et al. (1993). Territoriality in Lemur catta groups during the birth season at Berenty, Madagascar. In: Kappeler, P. M. & Ganzhorn, J. U. (eds), Lemur Social Systems and their Ecological Basis. New York: Plenum Press, pp. 85–109.
Judge, P. G. & Bachmann, K. A. (2013). Witnessing reconciliation reduces arousal of bystanders in a baboon group (Papio hamadryas hamadryas). Animal Behaviour, 85, 881–889.
Kaada, B. & Torsteinbø, O. (1989). Increase of plasma beta-endorphins in connective tissue massage. General Pharmacology, 20, 487–489.
Kappeler, P. M. (1990). Female dominance in Lemur catta: more than just female feeding priority?Folia Primatologica, 55, 92–95.
Keverne, E. B., Martensz, N. D. & Tuite, B. (1989). Beta-endorphin concentrations in cerebrospinal fluid of monkeys are influenced by grooming relationships. Psychoneuroendocrinology, 14, 155–161.
Kikusui, T., Winslow, J. T. & Mori, Y. (2006). Social buffering: relief from stress and anxiety. Philosophical Transactions of the Royal Society B: Biological Sciences, 361, 2215–2228.
Klein, Z. A., Padow, V. A. & Romeo, R. D. (2010). The effects of stress on play and home cage behaviors in adolescent male rats. Developmental Psychobiology, 52, 62–70.
Koski, S. E., Koops, K. & Sterck, E. H. M. (2007). Reconciliation, relationship quality and post-conflict anxiety: Testing the integrated hypothesis in captive chimpanzees. American Journal of Primatology, 69, 158–172.
Koyama, N. (1988). Mating behavior of ring-tailed lemurs (Lemur catta) at Berenty, Madagascar. Primates, 29, 163–174.
Koyama, N., Nakamichi, M., Ichino, S. & Takahata, Y. (2002). Population and social dynamics changes in ring-tailed lemur troops at Berenty, Madagascar between 1989–1999. Primates, 43, 291–314.
Krause, L. & Shuster, S. (1983). Mechanism of action of antipruritic drugs. British Medical Journal, 287, 1199–2000.
Kutsukake, N. (2003). Assessing relationship quality and social anxiety among wild chimpanzees using self-directed behaviour. Behaviour, 140, 1153–1171.
Kutsukake, N., & Castles, D. L. (2001). Reconciliation and variation in post-conflict stress in Japanese macaques (Macaca fuscata fuscata): testing the integrated hypothesis. Animal Cognition, 4, 259–268.
Leavens, D. A., Aureli, F., Hopkins, W. D. & Hyatt, C. W. (2001). Effects of cognitive challenge on self-directed behaviors by chimpanzees (Pan troglodytes). American Journal of Primatology, 55, 1–14.
Lehmann, H. E. (1979). Yawning. A homeostatic reflex and its psychological significance. Bulletin of the Menninger Clinic, 43, 123–126.
Leone, A., Ferrari, P. F. & Palagi, E. (2014). Different yawns, different functions? Testing social hypotheses on spontaneous yawning in Theropithecus gelada. Scientific Reports, 4.
Levine, S., Coe, C. L. & Smotherman, W. P. (1978). Prolonged cortisol elevation in the infant squirrel monkey after reunion with mother. Physiology and Behavior, 20, 7–10.
Lord, L. D., Bond, J. & Thompson, R. R. (2009). Rapid steroid influences on visually guided sexual behavior in male goldfish. Hormones and Behavior, 56, 519–526.
MacLean, P. D. (1990). The Triune Brain in Evolution: Role in Paleocerebral Functions. New York: Springer.
Maestripieri, D., Schino, G., Aureli, F. & Troisi, A. (1992). A modest proposal: displacement activities as an indicator of emotions in primates. Animal Behaviour, 44, 967–979.
Manogue, K. R., Leshner, A. I. & Candland, D. K. (1975). Dominance status and adrenocortical reactivity to stress in squirrel monkeys (Saimiri sciureus). Primates, 16, 457–463.
Maretti, G., Sorrentino, V., Finomana, A., Gamba, M. & Giacoma, C. (2010). Not just a pretty song: an overview of the vocal repertoire of Indri indri. Journal of Anthropological Sciences, 88, 151–165.
Massen, J. J. M., Vermunt, D. A. & Sterck, E. H. M. (2012). Male yawning is more contagious than female yawning among chimpanzees (Pan troglodytes). PLoS ONE, 7, (7) e40697.
McFarland, R. & Majolo, B. (2011). Reconciliation and the costs of aggression in wild Barbary macaques (Macaca sylvanus): a test of the integrated hypothesis. Ethology, 117, 928–937.
Mendl, M., Brooks, J., Basse, C., et al. (2010). Dogs showing separation-related behaviour exhibit a ‘pessimistic’ cognitive bias. Current Biology, 20, R839–R840.
Mendoza, S. P., Coe, C. L., Lowe, E. L. & Levine, S. (1978). The physiological response to group formation in adult male squirrel monkeys. Psychoneuroendocrinology, 3, 221–229.
Molesti, S. & Majolo, B. (2013). Grooming increases self-directed behaviour in wild Barbary macaques, Macaca sylvanus. Animal Behaviour, 86, 169–175.
Morgan, K. N. (2006). Is autism a stress disorder? What studies of non-autistic populations can tell us. In: Baron, M. G., Groden, J., Groden, G. & Lipsitt, L. P. (eds), Stress and Coping in Autism. Oxford: Oxford University Press.
Morris, D. (1977). Manwatching. A field guide to human behavior. New York: Harry N Abrams.
Mulder, E. J. H., Robles de Medina, P. G., Huizink, A. C., et al. (2002). Prenatal maternal stress: effects on pregnancy and the (unborn) child. Early Human Development, 70, 3–14.
Norscia, I. & Borgognini-Tarli, S. M. (2008). Ranging behavior and possible correlates of pair-living in southeastern avahis. International Journal of Primatology, 29, 153–171.
Norscia, I. & Palagi, E. (2011). Yawn contagion and empathy in Homo sapiens. PLoS ONE, 6, (12), e28472.
Norscia, I. & Palagi, E. (2016). She more than he: gender bias supports the empathic nature of yawn contagion in Homo sapiens. Royal Society Open Science, 3, 150459.
Norscia, I., Carrai, V. & Borgognini-Tarli, S. M. (2006). Influence of dry season, food quality and quantity on behavior and feeding strategy of Propithecus verreauxi in Kirindy, Madagascar. International Journal of Primatology, 27, 1001–1022.
Palagi, E. & Norscia, I. (2011). Scratching around stress: hierarchy and reconciliation make the difference in wild brown lemurs (Eulemur fulvus). Stress, 14, 93–97.
Palagi, E., Cordoni, G. & Borgognini-Tarli, S. M. (2004). Immediate and delayed benefits of play behaviour: new evidence from chimpanzees (Pan troglodytes). Ethology, 110, 949–962.
Palagi, E., Paoli, T. & Tarli, S. B. (2006). Short-term benefits of play behavior and conflict prevention in Pan paniscus. International Journal of Primatology, 27, 1257–1270.
Palagi, E., Leone, A., Mancini, G. & Ferrari, P. F. (2009). Contagious yawning in gelada baboons as a possible expression of empathy. PNAS, 106, 19262–19267.
Palagi, E., Dall'Olio, S., Demuru, E. & Stanyon, R. (2014). Exploring the evolutionary foundations of empathy: consolation in monkeys. Evolution and Human Behavior, 35, 341–349.
Paukner, A. & Anderson, J. R. (2006). Video-induced yawning in stumptail macaques (Macaca arctoides). Biology Letters, 2, 36–38.
Pavani, S., Maestripieri, D., Schino, G., Turillazzi, P. G. & Scucchi, S. (1991). Factors influencing scratching behaviour in long-tailed macaques. Folia Primatologica, 57, 34–38.
Pellis, S. M. & Pellis, V. C. (2009). The Playful Brain: Venturing to the Limits of Neuroscience. Oxford: Oneworld Publications.
Pereira, M. E. & Kappeler, P. M. (1997). Divergent systems of agonistic behaviour in lemurid primates. Behaviour, 134, 225–274.
Platek, S. M., Critton, S. R., Myers, T. E. & Gallup, G. G. (2003). Contagious yawning: the role of self-awareness and mental state attribution. Cognitive Brain Research, 17, 223–227.
Preston, S. D. & de Waal, F. B. M. (2002). Empathy: Its ultimate and proximate bases. Behavioral and Brain Sciences, 25, 1–71.
Price, J. S. (2003). Evolutionary aspects of anxiety disorders. Dialogues in Clinical Neurosciences, 5, 223–236.
Provine, R. R. (1986). Yawning as a stereotyped action pattern and releasing stimulus. Ethology, 72, 448–455.
Provine, R. R., Hamernik, H. B. & Curchack, B. C. (1987). Yawning: relation to sleeping and stretching in humans. Ethology, 76, 152–160.
Pyritz, L., Kappeler, P. M. & Fichtel, C. (2011). Coordination of group movements in wild red-fronted lemurs (Eulemur rufifrons): Processes and influence of ecological and reproductive seasonality. International Journal of Primatology, 32, 1325–1347.
Pyritz, L., Fichtel, C., Huchard, E., & Kappeler, P. M. (2013). Determinants and outcomes of decision-making, group coordination and social interactions during a foraging experiment in a wild primate. PLoS ONE, 8, e53144.
Richard, A. F. (1978). Behavioral Variation: Case Study of a Malagasy Lemur. Lewisburg: Bucknell University Press.
Romero, T., Castellanos, M. A. & de Waal, F. B. (2010). Consolation as possible expression of sympathetic concern among chimpanzees. PNAS, 107, 12110–12115.
Rothman, S. (1941). Physiology of itching. Physiological Reviews, 21, 357–381.
Rubin, K. H. & Burgess, K. (2001). Social withdrawal. In: Vasey, M. W. & Dadds, M. R. (eds), The Developmental Psychopathology of Anxiety. Oxford: Oxford University Press, pp. 407–434.
Saketos, M., Sharma, N. & Santoro, N. F. (1993). Suppression of the hypothalamic-pituitary- ovarian axis in normal women by glucocorticoids. Biology of Reproduction, 49, 1270–1276.
Sapolsky, R. M. (1982). The endocrine stress-response and social status in the wild baboon. Hormones and Behavior, 16, 279–292.
Sapolsky, R. M. (1983). Endocrine aspects of social instability in the olive baboon (Papio anubis). American Journal of Primatology, 5, 365–379.
Sapolsky, R. M. (1987). Stress, social status, and reproductive physiology in free-living baboons. In: Crews, D. (ed.), Psychobiology of Reproductive Behavior: An Evolutionary Perspective. Englewood Cliffs: Prentice-Hall, pp. 291–322.
Sapolsky, R. M. (1990). Stress in the wild. Scientific American, 262, 116–123.
Sapolsky, R. M. (1992). Cortisol concentrations and the social significance of rank instability among wild baboons. Psychoneuroendocrinology, 17, 701–709.
Sapolsky, R. M. (2005). The influence of social hierarchy on primate health. Science, 308, 648–652.
Sapolsky, R. M. & Ray, J. C. (1989). Styles of dominance and their endocrine correlates among wild olive baboons (Papio anubis). American Journal of Primatology, 18, 1–13.
Sauther, M. L. (1991). Reproductive behavior of free-ranging Lemur catta at Beza Mahafaly Special Reserve, Madagascar. American Journal of Physical Anthropology, 84, 463–477.
Sauther, M. L. (1993). Resource competition in wild populations of ringtailed lemurs (Lemur catta): implications for female dominance. In: Kappeler, P. M. & Ganzhorn, J. U. (eds), Lemur Social Systems and their Ecological Basis. New York: Plenum Press, pp. 135–152.
Sauther, M. L., & Sussman, R. W. (1993). A new interpretation of the social organization and mating system of the ringtailed lemur (Lemur catta). In: Kappeler, P. M. & Ganzhorn, J. U. (eds), Lemur Social Systems and their Ecological Basis. New York: Plenum Press, pp. 111–121.
Sauther, M. L., Sussman, R. W. & Gould, L. (1999). The socioecology of the ring-tailed lemur: Thirty-five years of research. Evolutionary Anthropology, 8, 120–132.
Schino, G. & Aureli, F. (2009). Reciprocal altruism in primates: partner choice, cognition, and emotions. Advances in the Study of Behavior, 39, 45–69.
Schino, G. & Aureli, F. (2010). Primate reciprocity and its cognitive requirements. Evolutionary Anthropology: Issues, News, and Reviews, 19, 130–135.
Schino, G., Scucchi, S., Maestripieri, D. & Turillazzi, P. G. (1988). Allogrooming as a tension-reduction mechanism: a behavioral approach. American Journal of Primatology, 16, 43–50.
Schino, G., Troisi, A., Perretta, G. & Monaco, V. (1991). Measuring anxiety in nonhuman primates: effect of lorazepam on macaque scratching. Pharmacology Biochemistry and Behavior, 38, 391–889.
Schino, G., Perretta, G., Taglioni, A. M., Monaco, V. & Troisi, A. (1996). Primate displacement activities as an ethopharmacological model of anxiety. Anxiety, 2, 186–191.
Schwitzer, C., Mittermeier, R. A., Johnson, S. E., et al. (2014). Averting lemur extinctions amid Madagascar's political crisis. Science, 343, 842–843.
Sclafani, V., Norscia, I., Antonacci, D. & Palagi, E. (2012). Scratching around mating: factors affecting anxiety in wild Lemur catta. Primates, 53, 247–254.
Shankly, K. (1988). Pathology of pruritus. Veterinary Clinics of North America, 18, 971–981.
Sheriff, M. J., Dantzer, B., Delehanty, B., Palme, R. & Boonstra, R. (2011). Measuring stress in wildlife: techniques for quantifying glucocorticoids. Oecologia, 166, 869–87.
Shulman, K. R. & Jones, G. E. (1996). The effectiveness of massage therapy intervention on reducing anxiety in the workplace. Journal of Applied Behavioral Science, 32, 160–173.
Smith, E. O. (1999). Yawning: an evolutionary perspective. Journal of Human Evolution, 14, 191–198.
Smith, O. A., Astley, C. A., Spelman, F. A., et al. (1993). Integrating behavior and cardiovascular responses: posture and locomotion. I. Static analysis. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, 265, R1458–R1468.
Smith, T. & O'Driscoll, M. L. (2003). Can massage induce relaxation? A review of the evidence. International Journal of Therapy and Rehabilitation, 10, 491–496.
Stangier, U., Heidenreich, T., Peitz, M., Lauterbach, W. & Clark, D. M. (2003). Cognitive therapy for social phobia: individual versus group treatment. Behaviour Research and Therapy, 41, 991–1007.
Sussman, R. W. (1977). Socialization, social structure, and ecology of two sympatric species of lemur. In: Chevalier-Skolnikoff, S. & Poirier, F. E. (eds), Primate BioSocial Development: Biological, Social and Ecological Determinants. New York: Garland, pp. 515–528.
Sussman, R. W. (1992). Male life histories and inter-group mobility among ring-tailed lemurs (Lemur catta). International Journal of Primatology, 13, 395–413.
Sussman, R. W. & Richard, A. F. (1974). The role of aggression among diurnal prosimians. In: Holloway, R. L. (ed.), Primate Aggression, Territoriality, and Xenophobia. San Francisco: Academic Press, pp. 50–76.
Tan, S. M., Jong, S. C., Chan, L. F., et al. (2013). Physician, heal thyself: The paradox of anxiety amongst house officers and work in a teaching hospital. Asia-Pacific Psychiatry, 5 (Suppl 1), 74–81.
Terry, R. L. (1970) Primate grooming as a tension reduction mechanism. The Journal of Psychology, 76, 129–136.
Thierry, B. (2004). Social epigenesis. In: Thierry, B., Singh, M. & Kaumanns, W. (eds), Macaque Societies: A Model for the Study of Social Organization, Cambridge University Press, pp. 267–290.
Thorsteinsson, E. B., James, J. E. & Gregg, M. E. (1998). Effects of video-relayed social support on hemodynamic reactivity and salivary cortisol during laboratory-based behavioral challenge. Health Psychology, 17, 436–444.
Tilbrook, A. J., Turner, A. I. & Clark, I. J. (2002). Effects of stress on reproduction in non-rodent mammals: the role of glucocorticoids and sex differences. Reviews of Reproduction, 5, 105–113.
Tinbergen, N. (1951). The Study of Instinct. New York: Oxford University Press.
Tran, B. W., Papoiu, A. D., Russoniello, C. V., et al. (2010). Effect of itch, scratching and mental stress on autonomic nervous system function in atopic dermatitis. Acta Dermato-Venereologica, 90, 354–361.
Troisi, A. (2002). Displacement activities as a behavioral measure of stress in nonhuman primates and human subjects. Stress, 5, 47–54.
Troisi, A., Aureli, F., Schino, G., Rinaldi, F. & de Angelis, N. (1990). The influence of age, sex, and rank on yawning behavior in two species of macaques (Macaca fascicularis and Macaca fuscata). Ethology, 86, 303–310.
Troisi, A., Belsanti, S., Bucci, A. R., et al. (2000). Affect regulation in alexithymia – an ethological study of displacement behavior during psychiatric interviews. The Journal of Nervous and Mental Disease, 188, 13–18.
Tuinier, S., Verhoeven, W. M. A. & Van Praag, H. M. (1996). Serotonin and disruptive behaviour; a critical evaluation of the clinical data. Human Psychopharmacology: Clinical and Experimental, 11, 469–482.
Valenstein, E. S. & Young, W. C. (1955). An experimental factor influencing the effectiveness of testosterone proprionate in eliciting sexual behavior in male guinea pigs. Endocrinology, 56, 173–185.
van Goozen, S. H. M. (2005). Hormones and the developmental origins of aggression. In: Tremblay, R. E., Hartup, W. W. & Archer, J. (eds), Developmental Origins of Aggression. New York: The Guilford Press.
van Moffaert, M. (2003). The spectrum of dermatological self-mutilation and self-destruction: common issues. In: Koo, J. Y. M. & Lee, C. S. (eds), Psychocutaneous Medicine. New York: Marcel Dekker, pp. 139–155.
van Riezen, H., & Segal, M. (1988). Introduction to the Evaluation of Anxiety and Related Disorders. Comparative Evaluation of Rating Scales for Clinical Psychopharmacology. New York: Elsevier, pp. 225–228.
van Wolkenten, M. L., Davis, J. M., Gong, M. L. & de Waal, F. B. (2006). Coping with acute crowding by Cebus apella. International Journal of Primatology, 27, 1241–1256.
Vick, L. G. & Pereira, M. E. (1989). Episodic targeting aggression and the histories of Lemur social groups. Behavioral Ecology and Sociobiology, 25, 3–12.
Vick, S. & Paukner, A. (2009). Variation and context of yawns in captive chimpanzees (Pan troglodytes). American Journal of Primatology, 71, 1–8.
Virgin, C. E. & Sapolsky, R. M. (1997). Styles of male social behavior and their endocrine correlates among low-ranking baboons. American Journal of Primatology, 42(1), 25–39.
Weaver, A. & de Waal, F. (2003). The mother-offspring relationship as a template in social development: reconciliation in captive brown capuchins (Cebus apella). Journal of Comparative Psychology, 117, 101–110.
Weissman, C. (1990). The metabolic response to stress: an overview and update. Anesthesiology, 73, 308–327.
Welch, J. M., Lu, J., Rodriguiz, R. M., et al. (2007). Cortico-striatal synaptic defects and OCD-like behaviours in Sapap3-mutant mice. Nature, 448, 894–900.
Whitten, P. L., Brockman, D. K. & Stavisky, R. C. (1998). Recent advances in noninvasive techniques to monitor hormone-behavior interactions. Yearbook of Physical Anthropology, 41, 1–23.
Wilson, J. H. (2001). Prolactin in rats is attenuated by conspecific touch in a novel environment. Cognitive, Affective, & Behavioral Neuroscience, 1, 199–205
Wingfield, J. C., Hegner, R. E., Dufty, A. M. & Ball, G. F. (1990). The challenge hypothesis: theoretical implications for patterns of testosterone secretion, mating systems, and breeding strategies. American Naturalist, 136, 829–846.
Wingfield, J. C. & Ramenofsky, M. (1999). Hormones and the behavioral ecology of stress. In: Balm, P. H. M. (ed.), Stress Physiology in Animals. Sheffield: Sheffield Academic Press, pp. 2–51.
Wright, A. J., Soto, N. A., Baldwin, A. L., et al. (2007). Anthropogenic noise as a stressor in animals: a multidisciplinary perspective. International Journal of Comparative Psychology, 20, 250–273.
Zannella, A., Norscia, I., Stanyon, R. & Palagi, E. (2015). Testing yawning hypotheses in wild populations of two strepsirrhine species: Propithecus verreauxi and Lemur catta. American Journal of Primatology, 77, 1207–1215.
Zilli, I., Giganti, F. & Uga, V. (2008). Yawning and subjective sleepiness in the elderly. Journal of Sleep Research, 17, 303–308.