Rebecca E. Frank

Dept. of Anthropology
University of California Los Angeles
Los Angeles, CA 90095




Curriculum Vitae


UCLA Anthropology


Behavior, Evolution, and Culture


Anthro Grads


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MA Thesis: Completed Winter 2001

Much of baboon social life is characterized by situations where interests conflict and costly signals ensure honesty.  But often interests are aligned, coordination is valued, or repeat interactions make deception unprofitable. Observations of two groups of baboons (Papio anubis) in Laikipia, Kenya, provide further evidence that low cost honest signals are important tools in facilitating social interactions.  Grunts did not significantly increase the likelihood of subsequent grooming, but did reduce the likelihood of conflict.  When conflicts occur, females rarely grunted before, but sometimes grunted to their opponent at the end of the conflict, prior to leaving.  This pattern of grunting after conflict provides further support that grunts play a role in reconciliation.  Groom presents often lead to subsequent grooming and seem to be the most effective signal in facilitating grooming.  Only some dyads use groom presents, suggesting that their effectiveness in facilitating grooming may be specific to partners with predictable grooming relationships.   The role of lipsmacking remains unclear.  Subsequent studies may be able to further clarify the role that specific signals play in facilitating affiliative interactions and avoiding conflict. 


Dissertation Research: June 2003 - December 2004

Exchange relationships are a fundamental part of human and nonhuman primate interaction. Humans rely on cooperation and reciprocity more than any other species, and evolutionary theory predicts that cooperation will be limited to kin or reciprocating partners.  However evidence for reciprocity among nonhuman primates is limited. Some researchers suggests that grooming and coalitionary support are contingently reciprocated within dyads (Seyfarth 1977).  Others question these data and emphasize that nonhuman primates mainly exchange low-cost commodities, like grooming or tolerance, over very short time scales (Henzi and Barrett 1999). These exchanges, it is argued, are regulated by biological markets which set “prices” for behavioral commodities and shape the dynamics of exchanges (Henzi and Barrett 1999).  Additionally, relationship quality affects the dynamics of grooming exchanges.  Females who groom each other frequently negotiate their interactions differently than females who do not groom frequently (Muroyama 1991).

Current tests of biological market models suggest that resource availability also affects grooming exchanges. When food resources are scarce and higher ranking females can control access to those resources, lower ranking females are expected to increase the amount of grooming they give to dominant partners in exchange for their tolerance during foraging (Henzi and Barrett 1999). When resources are not contested, tolerance is not valuable, and females will balance grooming regardless of rank differences (Henzi and Barrett 1999). Data show that grooming disparity increases when resources are patchy or scarce and rates of aggression are high (Barrett, Henzi et al. 1999; Barrett, Gaynor etal. 2002), but it is not clear how grooming disparities and tolerance are related within dyads or connected from one interaction to the next.

My dissertation research set out to (1) evaluate the patterning of cooperative exchanges among pairs of unrelated females, focusing on the dynamics of reciprocity within and between grooming interactions; (2) determine how the patterning of grooming within and across interactions is affected by the quality of the dyad’s relationship, the availability of resources, and the relative rank of the partners; (3) investigate the role of signals in negotiating grooming exchanges.