Abstract: Individuals consistently differ in behavioural phenotypes. Here we examine the interaction between behavioural phenotype and response to social context during novel object exploration in a neophobic corvid species, the raven (Corvus corax). The presence of conspecifics tends to encourage object exploration and learning but may also delay or even inhibit exploratory behaviour. Factors such as individual differences in response to social context may determine whether the presence of a conspecific facilitates or inhibits approach to novel objects. We confronted eleven six-month-old hand-raised ravens with novel objects, both individually and in dyadic combinations. We defined individuals as “fast” and “slow” explorers on the basis of their approach latency to novel objects when tested individually. The presence of a conspecific delayed the approach of fast birds to novel objects. Slow birds, in contrast, approached the novel objects with lower latencies and spent more time close to them when in dyads with fast siblings than when alone. The individuals" approach behaviour seemed to determine whether social context facilitated or delayed exploratory behaviour. This may contribute to explaining ambiguous results concerning the effects of social context in previous studies.

Abstract: In the present study, we sought to determine the influence of stress and temperament on working memory for disappearing food in horses. After assessment of five dimensions of temperament, we tested working memory of horses using a delayed-response task requiring a choice between two food locations. Delays ranging from 0 to 20 s were tested. The duration of working memory for disappearing food was first characterized without stressors (N = 26). The horses were then divided into two groups and their performance was assessed under stressful (exposure to acute stressors prior to testing, N = 12) or control conditions (N = 12). Results showed that the duration of working memory for disappearing food lasted at least 20 s under nonstressful conditions, and that under stressful conditions this duration lasted less than 12 s. This stress-induced impairment confirms in a nonrodent species that working memory performance is very sensitive to exposure to stressors. In addition, working memory performance in horses is influenced by the temperamental dimension of fearfulness according to the state of stress: fearful horses showed better performance under control conditions and worse performance under stressful conditions than nonfearful horses. These findings are discussed in the context of the Yerkes–Dodson law of stress and performance.

Abstract: Das Ziel der vorliegenden Studie war die Ermittlung der Kosten eines Verhaltenstests zur
objektiven Temperamentbeurteilung. Sie wurde an 1028 Pferden auf 55 Zuchtveranstaltungen
und Privatbetrieben ermittelt.
Weiterhin wurde eine Befragung zur allgemeinen Akzeptanz einer solchen Beurteilung
bei Reitpferden durchgeführt. Zusätzlich wurde mit Hilfe einer Online-Umfrage die
Meinung zu den Kosten und dem Aufwand einer solchen Beurteilung ermittelt. Die
Kosten der Einführung einer objektiven Temperamentbeurteilung entsprechen nach Einbeziehung
aller Faktoren ca. 18 Euro je Pferd. Den Kosten steht die Zahlungsbereitschaft
für eine verbesserte, da objektivierte Temperamentbeurteilung gegenüber. Insgesamt
56,7% der Befragten wären bereit, mehr als 11 Euro für eine objektive Interieurbeurteilung
auf Leistungsprüfungen im Feld zu investieren. Im Rahmen von Stationsprüfungen
wären sie sogar bereit mehr als 30 Euro aufzuwenden. Die Wertsteigerung eines im
Rahmen des Verfahrens positiv bewerteten Pferdes um 5%, die von den Teilnehmern der
Umfrage durchschnittlich angenommen wird, würde zusätzlich den Gewinn beim Pferdeverkauf
steigern. Die Ergebnisse zeigen, dass die Kosten einer objektiven Temperamentbeurteilung
durch eine erhöhte Zahlungsbereitschaft der Käufer scheinbar kompensiert
werden können, so dass die Einführung eines Temperamenttests zur objektiven Interieurbeurteilung
in Form der vorgestellten Untersuchungen grundsätzlich finanzierbar ist.
[The aim of the present study was to assess costs as well as riders’ acceptance of an
objective temperament evaluation in riding horses. Costs were determined based on a
novel object test conducted in 1028 horses tested on 65 occasions during performance
tests or in private stables. In addition, an online survey was used to identify riders’
opinion about the costs and benefits of such an assessment. Based on the conditions
assumed in the present study the costs for temperament testing have amount 18 Euro per
horse. More than 50% of the respondents were willing to pay more than 11 Euro for an
objective temperament assessment in their horses during performance tests in field.
Within performance tests on station they would spend more than 30 Euro for an objective temperament assessment. Participants further assumed a rise in value of favourably
assessed horses by 5%, leading to increased profits when selling the horse. In conclusion,
riders appear to be willing to cover the additional costs accrued from the temperament
test. Therefore, the introduction of an objective temperament assessment is likely to pay
off.]

Abstract: The social intelligence hypothesis argues that competition and cooperation among individuals have shaped the evolution of cognition in animals. What do we mean by social cognition? Here we suggest that the building blocks of social cognition are a suite of skills, ordered roughly according to the cognitive demands they place upon individuals. These skills allow an animal to recognize others by various means; to recognize and remember other animals' relationships; and, perhaps, to attribute mental states to them. Some skills are elementary and virtually ubiquitous in the animal kingdom; others are more limited in their taxonomic distribution. We treat these skills as the targets of selection, and assume that more complex levels of social cognition evolve only when simpler methods are inadequate. As a result, more complex levels of social cognition indicate greater selective pressures in the past. The presence of each skill can be tested directly through field observations and experiments. In addition, the same methods that have been used to compare social cognition across species can also be used to measure individual differences within species and to test the hypothesis that individual differences in social cognition are linked to differences in reproductive success.

Abstract: A comprehensive evolutionary framework for understanding the maintenance of heritable behavioral variation in humans is yet to be developed. Some evolutionary psychologists have argued that heritable variation will not be found in important, fitness-relevant characteristics because of the winnowing effect of natural selection. This article propounds the opposite view. Heritable variation is ubiquitous in all species, and there are a number of frameworks for understanding its persistence. The author argues that each of the Big Five dimensions of human personality can be seen as the result of a trade-off between different fitness costs and benefits. As there is no unconditionally optimal value of these trade-offs, it is to be expected that genetic diversity will be retained in the population.