Social Use of Facial Expressions in Hylobatids

Abstract Non-human primates use various communicative means in interactions with others. While primate gestures are commonly considered to be intentionally and flexibly used signals, facial expressions are often referred to as inflexible, automatic expressions of affective internal states. To explore whether and how non-human primates use facial expressions in specific communicative interactions, we studied five species of small apes (gibbons) by employing a newly established Facial Action Coding System for hylobatid species (Gibbon-FACS). We found that, despite individuals often being in close proximity to each other, in social (as opposed to non-social contexts) the duration of facial expressions was significantly longer when gibbons were facing another individual compared to non-facing situations. Social contexts included grooming, agonistic interactions and play, whereas nonsocial contexts included resting and self-grooming. Additionally, gibbons used facial expressions while facing another individual more often in social contexts than non-social contexts where facial expressions were produced regardless of the attentional state of the partner. Also, facial expressions were more likely 'responded to' by the partner's facial expressions when facing another individual than non-facing. Taken together, our results indicate that gibbons use their facial expressions differentially depending on the social context and are able to use them in a directed way in communicative interactions with other conspecifics

Paedomorphic facial expressions give dogs a selective advantage

How wolves were first domesticated is unknown. One hypothesis suggests that wolves underwent a process of self-domestication by tolerating human presence and taking advantage of scavenging possibilities. The puppy-like physical and behavioural traits seen in dogs are thought to have evolved later, as a byproduct of selection against aggression. Using speed of selection from rehoming shelters as a proxy for artificial selection, we tested whether paedomorphic features give dogs a selective advantage in their current environment. Dogs who exhibited facial expressions that enhance their neonatal appearance were preferentially selected by humans. Thus, early domestication of wolves may have occurred not only as wolf populations became tamer, but also as they exploited human preferences for paedomorphic characteristics. These findings, therefore, add to our understanding of early dog domestication as a complex co-evolutionary process

Social use of facial expressions in hylobatids

Non-human primates use various communicative means in interactions with others. While primate gestures are commonly considered to be intentionally and flexibly used signals, facial expressions are often referred to as inflexible, automatic expressions of affective internal states. To explore whether and how non-human primates use facial expressions in specific communicative interactions, we studied five species of small apes (gibbons) by employing a newly established Facial Action Coding System for hylobatid species (GibbonFACS). We found that, despite individuals often being in close proximity to each other, in social (as opposed to non-social contexts) the duration of facial expressions was significantly longer when gibbons were facing another individual compared to non-facing situations. Social contexts included grooming, agonistic interactions and play, whereas non-social contexts included resting and self-grooming. Additionally, gibbons used facial expressions while facing another individual more often in social contexts than non-social contexts where facial expressions were produced regardless of the attentional state of the partner. Also, facial expressions were more likely ‘responded to’ by the partner’s facial expressions when facing another individual than non-facing. Taken together, our results indicate that gibbons use their facial expressions differentially depending on the social context and are able to use them in a directed way in communicative interactions with other conspecifics

Wie versteht der Haushund (Canis familiaris) die menschliche Zeigegeste?

The present thesis concerns the social cognitive abilities of domestic dogs (Canis familiaris). It investigates the mechanism by which dogs comprehend human forms of communication. In particular, this thesis examines evidence for and against two hypotheses as to how dogs use human communication. The first is the command hypothesis. This hypothesis is based on the assumption that dogs do comprehend the human-given pointing gesture as an instruction to go in the direction the human is pointing at. The second is the information hypothesis. It states that dogs perceive the pointing gesture as pure information given to inform them about some entity in the environment. Study 1 investigates whether dogs would follow a human point to an empty spot without having experienced a context prior to the communicative situation. This was compared to another group of dogs which that had experienced such a context, i.e. finding food on the ground previously. The results showed that dogs do not follow a pointing gesture ‘blindly’. They did consider the contextual background of the situation and also the tone of voice of the experimenter when responding to the gesture. This finding is not explained by dogs simply associating the human’s hand with food. Study 2 focused on dogs’ comprehension of the pointing gesture in situations when they have experienced previously that the experimenter has a certain attitude. For some dogs the human is a reliable person, for another group she is unreliable. A third group experienced the human being authoritative and for a last group the human was non- authoritative. Results showed that dogs did not differentiate between the different conditions and followed the pointing gesture above chance level in all conditions. Study 3 of this dissertation investigated dogs’ behaviour when a human gives incorrect information about the location of hidden food. Sometimes dogs had information about the correct food location and sometimes not. Results showed that dogs did rely on their own visual experience when they knew where the food was hidden and ignored the misleading gesture. When they did not have information about the hidden food, they followed the human gesture. A second experiment in the same study suggested that being prevented from the visual access of the food hiding process does not change this behaviour pattern. Results from both experiments 1 and 2 of study 3 argue against an imperative understanding of the human- given pointing gesture in dogs and rather favour an informative understanding. 78 Study 4 examines the question of whether dogs would behave differently in an object choice task with the experimenter being either a 4,5-5-year-old child or an adult. Children are not considered to be high authoritative humans for dogs. A difference in their choice behaviour would have given support for the idea that dogs could understand the gesture as a command. Results showed that dogs did not differentiate between child and adult experimenters in this set- up. Additionally, dogs did follow a “sit” command from an adult more often compared to the same command given by a child. Taken together, these studies provide valuable insight into how dogs understand human forms of communication. The general observation that dogs do not follow the human given pointing gesture in every instance contradicts the command hypothesis, but does not necessarily favour the information hypothesis. However, the studies highlight the enormous flexibility in dogs’ point following behaviour and give ideas for future studies.Die vorliegende Arbeit beschäftigt sich mit den sozial-kognitiven Fähigkeiten von Haushunden (Canis familiaris). Sie untersucht die Mechanismen, die dem Verständnis von Hunden für menschliche Kommunikation zugrunde liegen. Im Einzelnen soll das Für und Wider folgender zwei Hypothesen untersucht werden. Die erste Hypothese ist die „Kommando-Hypothese“. Diese Hypothese beruht auf der Annahme, dass Hunde die menschliche Zeigegeste als Kommando betrachten, welchem sie zu folgen haben. Die zweite Hypothese ist die „Informations- Hypothese“. Diese geht davon aus, dass Hunde die menschliche Zeigegeste als reine Information ansehen, die sie über Gegebenheiten in der Umwelt informiert. Studie 1 zeigte, dass die Hunde den Kontext einer Situation berücksichtigten, wenn sie der menschlichen Zeigegeste folgten. Zusätzlich passten die Hunde ihr Verhalten an verschiedenen Stimmlagen des Menschen an. Das Verhalten der Hunde in dieser Studie ist nicht darauf zurückzuführen, dass die Hunde der Zeigegeste nur folgen, weil sie durch vorherige Erfahrungen die menschliche Hand mit einer Belohnung assoziiert haben. Die zweite Studie untersuchte, ob Hunde zwischen verschiedenen Verhaltensweisen (autoritär, antiautoritär, zuverlässig und unzuverlässig) unterscheiden, die der Mensch ihnen gegenüber in einer Etablierungsphase zeigte. In einem folgenden Objekt- Wahl-Test zeigten die Hunde aus allen vier Gruppen keine Unterschiede in ihrem Verhalten. Sie wählten denjenigen Becher, auf den der Mensch zeigte. Die Ergebnisse lassen vermuten, dass diese Information hier irrelevant für sie ist. In der dritten Studie hatten die Hunde in einem Objekt-Wahl-Test entweder beobachten können, wo das Futter versteckt wurde oder sie hatten keinen visuellen Zugang zu den Bechern, während des Versteckvorganges. Der Mensch zeigte in dieser Studie immer auf den leeren Becher. Zusätzlich wurde auch variiert, ob der Mensch anwesend oder abwesend ist, während der Hund einen Becher wählt. Es zeigte sich, dass die Hunde der Zeigegeste folgten, wenn sie nicht gesehen hatten, wo das Futterstück versteckt wurde. Haben sie aber vorher beobachten können, wo das Futter versteckt wurde, ignorierten sie die Zeigegeste und wählten den mit Futter bestückten Becher. Ob der Mensch anwesend war oder nicht, hatte keinen Einfluss auf das Verhalten der Hunde. Dieses Ergebnis widerspricht der Kommando- 80 Hypothese. Gemäß dieser Hypothese hätten die Hunde in jeder Situation der Zeigegeste folgen müssen. Eine weitere Studie, Studie 4, untersuchte, ob das Verhalten der Hunde in einem Objekt-Wahl-Test abhängig von dem Autoritätsstatus des Versuchsleiters ist. Hier zeigte entweder ein vier- bis viereinhalb-jähriges Kind oder ein Erwachsener auf einen von zwei Bechern, in dem das Futter zuvor versteckt wurde. Die Hunde folgten der Geste beider Versuchsleiter-Gruppen gleichermaßen. Die Hunde unterschieden wiederum zwischen den beiden Versuchsleiter-Typen, wenn ein klares „Sitz“-Kommando ausgesprochen wurde und folgten hier dem Erwachsenen, nicht aber dem Kind. Zusammenfassend sprechen die Ergebnisse der aufgeführten Studien gegen die Kommando-Hypothese, was aber nicht gleichzeitig Evidenz für die Informations-Hypothese liefert. Sie geben einen Einblick in das Verständnis menschlicher Kommunikation beim Hund und heben seine besondere Flexibilität in diesem Verhalten hervor. Sie liefern Anlass und Ideen für zukünftige Studien

Compositionality in emotional expressions of chimpanzees

This project is part of a multi-disciplinary project (GRAMBY - The Grammar of the Body) in which we aim to reveal the foundations of compositionality in human language. Compositionality is a fundamental principle of language structure, according to which the meanings of complex expressions are determined by the meanings of their constituents and the way in which they combine (e.g. Jackendoff, 2011). The GRAMBY framework is inspired by sign language, in which different components of language are signalled by the hands, face and body (Sandler, 2012). This paradigm is taken a step further by investigating a more basic level of human communication: the expression of extreme emotion by different parts of the face and body (Cavicchio & Sandler, 2015). It has been shown clearly that communication in our closest living relatives, the great apes, is multimodal (Liebal et al., 2014). However, it is not known how signals from different modalities (face, hands, body) combine. In this project, we seek precursors of linguistic compositionality in the emotional and communicative bodily signals of chimpanzees. Our hypothesis is that the compositionality of embodied emotional communication played a role in the evolution of the compositionality of language

Do domestic dogs interpret pointing as a command?

Domestic dogs comprehend human gestural communication flexibly, particularly the pointing gesture. Here, we examine whether dogs interpret pointing informatively, that is, as simply providing information, or rather as a command, for example, ordering them to move to a particular location. In the first study a human pointed toward an empty cup. In one manipulation, the dog either knew or did not know that the designated cup was empty (and that the other cup actually contained the food). In another manipulation, the human (as authority) either did or did not remain in the room after pointing. Dogs ignored the human's gesture if they had better information, irrespective of the authority's presence. In the second study, we varied the level of authority of the person pointing. Sometimes this person was an adult, and sometimes a young child. Dogs followed children's pointing just as frequently as they followed adults' pointing (and ignored the dishonest pointing of both), suggesting that the level of authority did not affect their behavior. Taken together these studies suggest that dogs do not see pointing as an imperative command ordering them to a particular location. It is still not totally clear, however, if they interpret it as informative or in some other way.</p

Results of likelihood ratio tests of GLMM.

<p>Cut-off refers to the time interval between the consecutive facial expressions.</p

Estimates and Std.

<p>Errors for the coefficients of the two above-mentioned full models.</p

Type of facial expressions used exclusively when facing another individual, those used exclusively when not facing another individual, and those that occurred in both facing and non-facing situations.

<p>For more details on the morphology regarding previous descriptions of these facial expressions, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151733#pone.0151733.s002" target="_blank">S2 Table</a>. All facial expressions including AU10, AU16, AU25, AU26, AU27 are forms of ‘open-mouth’ displays [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151733#pone.0151733.ref023" target="_blank">23</a>]. Frequencies and other details are reported in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151733#pone.0151733.s002" target="_blank">S2</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0151733#pone.0151733.s003" target="_blank">S3</a> Tables.</p