Comparing responses of four ungulate species to playbacks of baboon alarm calls

A growing body of evidence suggests that a wide range of animals can recognize and respond appropriately to calls produced by other species. Social learning has been implicated as a possible mechanism by which heterospecific call recognition might develop. To examine whether familiarity and/or shared vulnerability with the calling species might influence the ability of sympatric species to distinguish heterospecific alarm calls, we tested whether four ungulate species (impala: Aepyceros melampus; tsessebe: Damaliscus lunatus; zebra: Equus burchelli; wildebeest: Connochaetes taurinus) could distinguish baboon (Papio hamadryas ursinus) alarm calls from other loud baboon calls produced during intra-specific aggressive interactions (‘contest’ calls). Overall, subjects’ responses were stronger following playback of alarm calls than contest calls. Of the species tested, impala showed the strongest responses and the greatest difference in composite response scores, suggesting they were best able to differentiate call types. Compared with the other ungulate species, impala are the most frequent associates of baboons. Moreover, like baboons, they are susceptible to both lion and leopard attacks, whereas leopards rarely take the larger ungulates. Although it seems possible that high rates of association and/or shared vulnerability may influence impala’s greater ability to distinguish among baboon call types, our results point to a stronger influence of familiarity. Ours is the first study to compare such abilities among several community members with variable natural histories, and we discuss future experiments that would more systematically examine development of these skills in young ungulates.     

Assessing Sequential Knowledge through Performance Measures: The Influence of Short-term Sequential Effects

Studies on implicit sequence learning have employed the methodology oftask dissociations to show that tasks of conscious memory fail to reveal knowledge expressed in performance measures of learning. One critical requirement of this methodology is that the conscious memory tests tap the same type of information that is expressed in performance measures. When a deterministic sequence is being repeated during practice, identification of the exact type of sequential information that is learned can be achieved by a trial-by-trial comparison between the practised sequence and a control sequence. In Experiment 1 we examine whether short-term sequential effects are present in choice response time tasks and may therefore contaminate this trial-by-trial comparison. In Experiment 2 we control for these effects and demonstrate how specification of the exact sub-parts of the sequence that are learned is necessary before testing for task dissociations. Our findings indicate a dissociation between a response time task and a free generation task. This dissociation, however, is obtained for selected sub-parts of the sequence and may be caused by the insensitivity of the free-generation task to low confidence knowledge.     

The Question of the Holocaust's Uniqueness: Was it Something More Than or Different From Genocide?

Dating back to the very beginning of our knowledge of the events that constituted the Holocaust, some historians, social scientists, philosophers, theologians and public intellectuals argue that it was a unique historical, or even trans‐historical, event. The aim of this article is to clarify what the uniqueness question should be about and to ascertain whether there are good reasons for judging that the Holocaust is unique. It examines the core meanings of ‘unique’ that feature in the literature and identifies which of these is most apt for considering the possible uniqueness of the Holocaust. It then works out what it would take for the Holocaust to be unique in the appropriately rigorous sense, which is facilitated by inquiring into the nature of genocide. The key question turns on the relation of the Holocaust to genocide: was the Holocaust more than, or different from, genocide?