UC Berkeley

Dogs (Canis familiaris) are strongly responsive to human influence in general, and they also readily form preferences for specific humans, yet these lines of inquiry have not often been combined. The goal of this dissertation was to advance a more specific theory regarding the nature of the dog-human bond - that it is one characterized by dependency - and to investigate whether such bonds would influence dogs to use social strategies to solve non-social problems.

In Chapter 1, I describe the features of the relationship between the dog as a species and humans, and how this inter-species relationship is reflected in the dog's attentiveness to humans and tendency to solve problems by attending to human behavior. After describing the dog's abilities in this domain, I go on to explore the phenomenon from the perspective of two of Tinbergen's four levels of analysis: phylogeny and ontogeny. To do this, I compare the dog's reading of human social cues with that of related canid species, and I then explore within-species differences among canines. Finally, I advance a new theory that dogs can be described as uniquely dependent on humans, and I explore various specific situations in which this dependency can explain the dog's problem solving strategy choices.

In Chapter 2, I explore experimentally whether the presence of social information provided by familiar versus unfamiliar humans would influence the dog's performance when choosing between two potential food sources. This study included a number of conditions; in some conditions, a familiar person indicated a container that gave food and a stranger indicated a container that did not; in other conditions this was reversed. Results show that dogs consistently chose the container indicated by or nearest to their owner, even when this container never yielded a food reward. In contrast, in two other conditions, dogs chose at chance: a control condition in which both humans were strangers, and a condition in which the owner and stranger sat reading books and provided no social signal to the dog. These results support the dependency hypothesis in showing that the dog's performance is either facilitated or hindered, depending on whether a familiar human provides accurate or inaccurate signals.

In Chapter 3, I explore the boundary conditions of the effect of familiarity on dogs' performance when choosing between potential food sources, by examining whether a brief period of familiarization with a new person would be enough for a dog to establish a preference for that person's social signal over that of a stranger. Results were not significant; some individual dogs showed a preference for a food container indicated by the familiar person, whereas others did not, but this effect was not significant at the group level. Future studies should incrementally increase the period of time used to familiarize the dog and the new person, to establish how long it takes for such a preference to form in the dog. Such findings would establish whether dogs can quickly become influenced by the information of a familiar person, without that particular dog needing to be in a state of actual dependency on that particular person, or whether dogs need a longer time period, and an actual level of dependence on a person, for this effect to occur. If actual dependency is not required, this would indicate that dependent-like responses in dogs are an automatic part of their responsiveness to familiar people, owing to such a strategy having resulted in fitness benefits over the history of the species, regardless of whether those familiar people actually materially provision the dog.

Finally, in Chapter 4, I explore the influence of variations in the relationship between specific dogs and owners on the dog's food-choice strategies by examining whether "closeness to owner" could predict the strength of the dog's preference for a food container indicated by the owner, among dogs tested in Chapters 2 and 3. I measured closeness by creating an owner-report survey which owners completed online. Factor analysis of a large community sample of owners revealed that this set of questions yielded two discrete scales: Owner-Initiated Closeness and Dog-Initiated Closeness. I examined correlations between these two scales and the performance of dogs tested in the previous chapters. Results were generally not significant; closeness scores did not explain variation in the strength of the dog's preference for their owner's signal. Future studies should explore more detailed ways of measuring closeness (e.g., by observing dogs and owners in their homes), and should examine whether dependence specifically, rather than closeness, might better explain differences in performance between dogs.