What is the role of mothers in the acquisition of termite-fishing behaviors in wild chimpanzees (Pan troglodytes schweinfurthii)?

This paper explores the role of maternal influences on the acquisition of a tool-using task in wild chimpanzees (Pan troglodytes schweinfurthii) in order to build on and complement previous work done in captivity. Young chimpanzees show a long period of offspring dependency on mothers and it is during this period that offspring learn several important skills, especially how to and on what to forage. At Gombe National Park, one skill that is acquired during dependency is termite-fishing, a complex behavior that involves inserting a tool made from the surrounding vegetation into a termite mound and extracting the termites that attack and cling to the tool. All chimpanzees observed at Gombe have acquired the termite-fishing skill by the age of 5.5 years. Since the mother is the primary source of information throughout this time period, I investigated the influence of mothers' individual termite-fishing characteristics on their offsprings' speed of acquisition and proficiency at the skill once acquired. Mother's time spent alone or with maternal family members, which is highly correlated to time spent termite-fishing, was positively correlated to offspring's acquisition of critical elements of the skill. I also investigated the specific types of social interactions that occur between mothers and offspring at the termite mound and found that mothers are highly tolerant to offspring, even when the behavior of the offspring may disrupt the termite-fishing attempt. However, no active facilitation by mothers of offsprings' attempts were observed. Electronic Supplementary Material Electronic supplementary material Supplementary material is available for this article at http://dx.doi.org/10.1007/s10071-005-0002-7 and accessible for authorised users.     

Visual kin recognition in nonhuman primates: (Pan troglodytes and Macaca mulatta): inbreeding avoidance or male distinctiveness?

Faces provide important information about identity, age, and even kinship. A previous study in chimpanzees reported greater similarity between the faces of mothers and sons compared with mothers and daughters, or unrelated individuals. This was interpreted as an inbreeding avoidance mechanism where females, the dispersing gender, should avoid mating with any male that resembles their mother. Alternatively, male faces may be more distinctive than female faces, biasing attention toward males. To test these hypotheses, chimpanzees and rhesus monkeys matched conspecifics' faces of unfamiliar mothers and fathers with their sons and daughters. Results showed no evidence of male distinctiveness, rather a cross-gender effect was found: chimpanzees were better matching moms with sons and fathers with daughters. Rhesus monkeys, however, showed an overwhelming bias toward male-distinctiveness. They were faster to learn male faces, performed better on father-offspring and parent-son trials, and were best matching fathers with sons. This suggests that for the rhesus monkey, inbreeding avoidance involves something other than facial phenotypic matching but that among chimpanzees, the visual recognition of facial similarities may play an important role.     

Attention biases and habituation of attention biases are associated with 5-HTTLPR and COMTval158met

Fundamental biases in affective information processing are modulated by individual differences in the emotional response to environmental stimuli that may be partly based on the individual’s genetic make-up. To extend prior dot probe studies on attention genetics, we used a visual-search paradigm (VSP) with pictures of angry and happy faces of both sexes as targets, neutral faces as distractors, and a varying set size. Participants were selected a priori depending on their 5-HTTLPR (s/s, s/l, l/l; on a constant rs25531 A-allele background) and COMTval158met (val/val, valmet, met/met) genotypes and were matched for sex and age. We demonstrate a bias towards angry male faces (as opposed to happy male faces) irrespective of 5-HTTLPR genotype in the first experimental block that was maintained during the second experimental block only in carriers of the s-allele, which implies differential habituation processes. While a bias towards angry male faces was observed irrespective of COMTval158met genotype, only individuals with the val/val genotype exhibited a bias towards a happy female face (as opposed to an angry female face). In sum, our results both replicate and extend prior findings in the field of attention genetics and add important pieces of information to the research on attentional biases in emotion processing.     

Fear expression and return of fear following threat instruction with or without direct contingency experience

Prior research showed that mere instructions about the contingency between a conditioned stimulus (CS) and an unconditioned stimulus (US) can generate fear reactions to the CS. Little is known, however, about the extent to which actual CS–US contingency experience adds anything beyond the effect of contingency instructions. Our results extend previous studies on this topic in that it included fear potentiated startle as an additional dependent variable and examined return of fear (ROF) following reinstatement. We observed that CS–US pairings can enhance fear reactions beyond the effect of contingency instructions. Moreover, for all measures of fear, instructions elicited immediate fear reactions that could not be completely overridden by subsequent situational safety information. Finally, ROF following reinstatement for instructed CS+s was unaffected by actual experience. In summary, our results demonstrate the power of contingency instructions and reveal the additional impact of actual experience of CS–US pairings.     

Genetic Gating of Human Fear Learning and Extinction: Possible Implications for Gene-Environment Interaction in Anxiety Disorder

ABSTRACT— Pavlovian fear conditioning is a widely used model of the acquisition and extinction of fear. Neural findings suggest that the amygdala is the core structure for fear acquisition, whereas prefrontal cortical areas are given pivotal roles in fear extinction. Forty-eight volunteers participated in a fear-conditioning experiment, which used fear potentiation of the startle reflex as the primary measure to investigate the effect of two genetic polymorphisms (5-HTTLPR and COMTval158met) on conditioning and extinction of fear. The 5-HTTLPR polymorphism, located in the serotonin transporter gene, is associated with amygdala reactivity and neuroticism, whereas the COMTval158met polymorphism, which is located in the gene coding for catechol-O-methyltransferase (COMT), a dopamine-degrading enzyme, affects prefrontal executive functions. Our results show that only carriers of the 5-HTTLPR s allele exhibited conditioned startle potentiation, whereas carriers of the COMT met/met genotype failed to extinguish conditioned fear. These results may have interesting implications for understanding gene-environment interactions in the development and treatment of anxiety disorders.