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Search Results: 1 - 10 of 498640 matches for " Elisabeth H. M. Sterck "
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Generous Leaders and Selfish Underdogs: Pro-Sociality in Despotic Macaques
Jorg J. M. Massen,Lisette M. van den Berg,Berry M. Spruijt,Elisabeth H. M. Sterck
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009734
Abstract: Actively granting food to a companion is called pro-social behavior and is considered to be part of altruism. Recent findings show that some non-human primates behave pro-socially. However, pro-social behavior is not expected in despotic species, since the steep dominance hierarchy will hamper pro-sociality. We show that some despotic long-tailed macaques do grant others access to food. Moreover, their dominance hierarchy determines pro-social behavior in an unexpected way: high-ranking individuals grant, while low-ranking individuals withhold their partner access to food. Surprisingly, pro-social behavior is not used by subordinates to obtain benefits from dominants, but by dominants to emphasize their dominance position. Hence, Machiavellian macaques rule not through “fear above love”, but through “be feared when needed and loved when possible”.
Male Yawning Is More Contagious than Female Yawning among Chimpanzees (Pan troglodytes)
Jorg J. M. Massen, Dorith A. Vermunt, Elisabeth H. M. Sterck
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0040697
Abstract: Yawn contagion is not restricted to humans and has also been reported for several non-human animal species, including chimpanzees (Pan troglodytes). Contagious yawning may lead to synchronisation of behaviour. However, the function of contagious yawning is relatively understudied. In this study, we investigated the function of contagious yawning by focusing on two types of signal providers: close social associates and leaders. We provided a captive chimpanzee colony with videos of all individuals of their own group that were either yawning, or at rest. Consistent with other studies, we demonstrated that yawning is contagious for chimpanzees, yet we did not find any effect of relationship quality on yawn contagion. However, we show that yawn contagion is significantly higher when the video model is a yawning male than when the video model was a yawning female, and that this effect is most apparent among males. As males are dominant in chimpanzee societies, male signals may be more relevant to the rest of the group than female signals. Moreover, since chimpanzees form male-bonded societies, male signals are especially relevant for other males. Therefore, we suggest that the sex-differences of yawning contagion among chimpanzees reflect the function of yawning in the synchronisation of behaviour.
Chimpanzees (Pan troglodytes) Fail a What-Where-When Task but Find Rewards by Using a Location-Based Association Strategy
Marusha Dekleva,Valérie Dufour,Han de Vries,Berry M. Spruijt,Elisabeth H. M. Sterck
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016593
Abstract: Recollecting the what-where-when of an episode, or episodic-like memory, has been established in corvids and rodents. In humans, a linkage between remembering the past and imagining the future has been recognised. While chimpanzees can plan for the future, their episodic-like memory has hardly been investigated. We tested chimpanzees (Pan troglodytes) with an adapted food-caching paradigm. They observed the baiting of two locations amongst four and chose one after a given delay (15 min, 1 h or 5 h). We used two combinations of food types, a preferred and a less preferred food that disappeared at different rates. The subjects had to base their choices on the time elapsed since baiting, and on their memory of which food was where. They could recover either their preferred food or the one that remained present. All animals failed to obtain the preferred or present foods above chance levels. They were like-wise unsuccessful at choosing baited cups above chance levels. The subjects, thus, failed to use any feature of the baiting events to guide their choices. Nonetheless, their choices were not random, but the result of a developed location-based association strategy. Choices in the second half of the study correlated with the rewards obtained at each location in the first half of the study, independent from the choices made for each location in the first half of the study. This simple location-based strategy yielded a fair amount of food. The animals' failure to remember the what-where-when in the presented set-up may be due to the complexity of the task, rather than an inability to form episodic-like memories, as they even failed to remember what was where after 15 minutes.
Better Safe than Sorry - Socio-Spatial Group Structure Emerges from Individual Variation in Fleeing, Avoidance or Velocity in an Agent-Based Model
Ellen Evers, Han de Vries, Berry M. Spruijt, Elisabeth H. M. Sterck
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026189
Abstract: In group-living animals, such as primates, the average spatial group structure often reflects the dominance hierarchy, with central dominants and peripheral subordinates. This central-peripheral group structure can arise by self-organization as a result of subordinates fleeing from dominants after losing a fight. However, in real primates, subordinates often avoid interactions with potentially aggressive group members, thereby preventing aggression and subsequent fleeing. Using agent-based modeling, we investigated which spatial and encounter structures emerge when subordinates also avoid known potential aggressors at a distance as compared with the model which only included fleeing after losing a fight (fleeing model). A central-peripheral group structure emerged in most conditions. When avoidance was employed at small or intermediate distances, centrality of dominants emerged similar to the fleeing model, but in a more pronounced way. This result was also found when fleeing after a fight was made independent of dominance rank, i.e. occurred randomly. Employing avoidance at larger distances yielded more spread out groups. This provides a possible explanation of larger group spread in more aggressive species. With avoidance at very large distances, spatially and socially distinct subgroups emerged. We also investigated how encounters were distributed amongst group members. In the fleeing model all individuals encountered all group members equally often, whereas in the avoidance model encounters occurred mostly among similar-ranking individuals. Finally, we also identified a very general and simple mechanism causing a central-peripheral group structure: when individuals merely differed in velocity, faster individuals automatically ended up at the periphery. In summary, a central-peripheral group pattern can easily emerge from individual variation in different movement properties in general, such as fleeing, avoidance or velocity. Moreover, avoidance behavior also affects the encounter structure and can lead to subgroup formation.
The EMO-Model: An Agent-Based Model of Primate Social Behavior Regulated by Two Emotional Dimensions, Anxiety-FEAR and Satisfaction-LIKE
Ellen Evers, Han de Vries, Berry M. Spruijt, Elisabeth H. M. Sterck
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0087955
Abstract: Agent-based models provide a promising tool to investigate the relationship between individuals’ behavior and emerging group-level patterns. An individual’s behavior may be regulated by its emotional state and its interaction history with specific individuals. Emotional bookkeeping is a candidate mechanism to keep track of received benefits from specific individuals without requiring high cognitive abilities. However, how this mechanism may work is difficult to study in real animals, due to the complexity of primate social life. To explore this theoretically, we introduce an agent-based model, dubbed EMO-model, in which we implemented emotional bookkeeping. In this model the social behaviors of primate-like individuals are regulated by emotional processes along two dimensions. An individual’s emotional state is described by an aversive and a pleasant dimension (anxiety and satisfaction) and by its activating quality (arousal). Social behaviors affect the individuals’ emotional state. To implement emotional bookkeeping, the receiver of grooming assigns an accumulated affiliative attitude (LIKE) to the groomer. Fixed partner-specific agonistic attitudes (FEAR) reflect the stable dominance relations between group members. While the emotional state affects an individual’s general probability of executing certain behaviors, LIKE and FEAR affect the individual’s partner-specific behavioral probabilities. In this way, emotional processes regulate both spontaneous behaviors and appropriate responses to received behaviors, while emotional bookkeeping via LIKE attitudes regulates the development and maintenance of affiliative relations. Using an array of empirical data, the model processes were substantiated and the emerging model patterns were partially validated. The EMO-model offers a framework to investigate the emotional bookkeeping hypothesis theoretically and pinpoints gaps that need to be investigated empirically.
Population-Specific Use of the Same Tool-Assisted Alarm Call between Two Wild Orangutan Populations (Pongopygmaeus wurmbii) Indicates Functional Arbitrariness
Adriano R. Lameira, Madeleine E. Hardus, Kim J. J. M. Nouwen, Eva Topelberg, Roberto A. Delgado, Berry M. Spruijt, Elisabeth H. M. Sterck, Cheryl D. Knott, Serge A. Wich
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069749
Abstract: Arbitrariness is an elementary feature of human language, yet seldom an object of comparative inquiry. While arbitrary signals for the same function are relatively frequent between animal populations across taxa, the same signal with arbitrary functions is rare and it remains unknown whether, in parallel with human speech, it may involve call production in animals. To investigate this question, we examined a particular orangutan alarm call – the kiss-squeak – and two variants – hand and leaf kiss-squeaks. In Tuanan (Central Kalimantan, Indonesia), the acoustic frequency of unaided kiss-squeaks is negatively related to body size. The modified variants are correlated with perceived threat and are hypothesized to increase the perceived body size of the sender, as the use of a hand or leaves lowers the kiss-squeak’s acoustic frequency. We examined the use of these variants in the same context in another orangutan population of the same sub-species and with partially similar habitat at Cabang Panti (West Kalimantan, Indonesia). Identical analyses of data from this site provided similar results for unaided kiss-squeaks but dissimilar results for hand and leaf kiss-squeaks. Unaided kiss-squeaks at Cabang Panti were emitted as commonly and showed the same relationship to body size as in Tuanan. However, at Cabang Panti, hand kiss-squeaks were extremely rare, while leaf-use neither conveyed larger body size nor was related to perceived threat. These findings indicate functional discontinuity between the two sites and therefore imply functional arbitrariness of leaf kiss-squeaks. These results show for the first time the existence of animal signals involving call production with arbitrary function. Our findings are consistent with previous studies arguing that these orangutan call variants are socially learned and reconcile the role of gestures and calls within evolutionary theories based on common ancestry for speech and music.
Commensurability effects in superconducting Nb films with quasiperiodic pinning arrays
M. Kemmler,C. Guerlich,A. Sterck,H. Poehler,M. Neuhaus,M. Siegel,R. Kleiner,D. Koelle
Physics , 2006, DOI: 10.1103/PhysRevLett.97.147003
Abstract: We study experimentally the critical depinning current Ic versus applied magnetic field B in Nb thin films which contain 2D arrays of circular antidots placed on the nodes of quasiperiodic (QP) fivefold Penrose lattices. Close to the transition temperature Tc we observe matching of the vortex lattice with the QP pinning array, confirming essential features in the Ic(B) patterns as predicted by Misko et al. [Phys. Rev. Lett, vol.95, 177007 (2005)]. We find a significant enhancement in Ic(B) for QP pinning arrays in comparison to Ic in samples with randomly distributed antidots or no antidots.
Die Q-Methode. Ein innovatives Verfahren zur Erhebung subjektiver Einstellungen und Meinungen Q-Sort Technique and Q-Methodology—Innovative Methods for Examining Attitudes and Opinions Técnica tipo-Q y metodología-Q. Métodos innovadores para reconocer actitudes y opiniones
Florian H. Müller,Elisabeth Kals
Forum : Qualitative Social Research , 2004,
Abstract: Die Q-Methode ist in der Tradition der deutschsprachigen Sozialforschung kaum bekannt. Die Q-Methode versteht sich als Forschungszugang an der Schnittstelle von qualitativen und quantitativen Methoden und wird besonders zur Erfassung komplexer Meinungsbilder, Einstellungen und Wertorientierungen aus subjektiver Perspektive verwendet. In diesem Beitrag wird die Q-sort Technik (als Erhebungsverfahren) und ihre zugrundegelegte Methodologie beschrieben sowie deren vielf ltigen Anwendungsm glichkeiten für eine qualitativ orientierte Markt-, Meinungs- und Medienforschung aufgezeigt. Die Bedeutung der Q-Methode für Einzelfallstudien, für die explorative Bildung von Personentypen, für kombinierte Verfahren von qualitativen und quantitativen Methoden wird dabei hervorgehoben sowie auf den innovativen Charakter der Methode für qualitativ arbeitende Forscherinnen und Forscher hingewiesen. URN: urn:nbn:de:0114-fqs0402347 In the German tradition of social sciences Q-method is not well known. Q-method combines both qualitative and quantitative research and is used to examine complex subjective structures like opinions, attitudes and values. This paper presents an introduction to Q-technique and its underlying methodology. The various applications of the method for a qualitative orientated research in the fields of market, opinion and media are also listed. The significance of the method for single case studies, for exploratory cluster analysis and for a combined application of qualitative and quantitative research strategies is emphasized. URN: urn:nbn:de:0114-fqs0402347 El método-Q no es muy conocido en la tradición alemana de las ciencias sociales. El método-Q combina la investigación cualitativa y cuantitativa y se utiliza para reconocer las estructuras subjetivas complejas como opiniones, actitudes y valores. Este artículo presenta una introducción a la técnica-Q y a su metodología subyacente. También se recogen las variadas aplicaciones del método para una investigación de orientación cualitativa en el campo del mercado, la opinión y los medios de comunicación. Se enfatiza la significación del método para los estudio de caso único, para el análisis de cluster exploratorio y para una aplicación combinada de estrategias de investigación cualitativa y cuantitativa. URN: urn:nbn:de:0114-fqs0402347
The Chlamydia pneumoniae Invasin Protein Pmp21 Recruits the EGF Receptor for Host Cell Entry
Katja M?lleken,Elisabeth Becker,Johannes H. Hegemann
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003325
Abstract: Infection of mammalian cells by the strictly intracellular pathogens Chlamydiae requires adhesion and internalization of the infectious Elementary Bodies (EBs). The components of the latter step were unknown. Here, we identify Chlamydia pneumoniae Pmp21 as an invasin and EGFR as its receptor. Modulation of EGFR surface expression evokes correlated changes in EB adhesion, internalization and infectivity. Ectopic expression of EGFR in EGFR-negative hamster cells leads to binding of Pmp21 beads and EBs, thus boosting the infection. EB/Pmp21 binding and invasion of epithelial cells results in activation of EGFR, recruitment of adaptors Grb2 and c-Cbl and activation of ERK1/2, while inhibition of EGFR or MEK kinase activity abrogates EB entry, but not attachment. Binding of Grb2 and c-Cbl by EGFR is essential for infection. This is the first report of an invasin-receptor interaction involved in host-cell invasion by any chlamydial species.
Dry-season retreat and dietary shift of the dart-poison frog Dendrobates tinctorius (Anura: Dendrobatidae)
Marga Born,Frans Bongers,Erik H. Poelman,Frank J. Sterck
Phyllomedusa : Journal of Herpetology , 2010,
Abstract: Seasonal rainfall affects tropical forest dynamics and behaviorof species that are part of these ecosystems. The positive correlation between amphibian activity patterns and rainfall has been demonstrated repeatedly. Members of Dendrobatidae, a clade of Neotropical dart-poison frogs, are well known for their habitat use and behavior during the rainy season, but their behavior during the dry season has received little attention. We studied habitat use and diet of the dendrobatid frog Dendrobates tinctorius in French Guiana during the rainy and dry seasons. Unlike many other dendrobatid frogs, D. tinctorius does not maintain territories for the entire rainy season. Both sexes colonize recently formed canopy-gaps and stay in these forest patches for only a few weeks. The frogs inthese patches consume a great diversity of prey, consisting of ants, beetles, wasps, insect larvae, and mites. During the dry season, frogs move to retreat sites in mature forest, such as palm bracts and tree holes. The frogs are less active and consume fewer prey items in the dry season, and they consume fewer wasps and insect larvae, but more termites. Ants are the most common prey items during both the wet and dry seasons. We discuss the effects of shifts in seasonal habitat use on the territorial behavior of dendrobatid frogs.
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