Human-directed sociability in the domestic dog: A Tinbergian approach.

The motivation to interact with humans is central to dogs' domestication process. This review aims to provide a curated overview of the current knowledge about dogs' human-directed sociability using Tinbergen's four questions as a guiding framework. Firstly, we explore its evolutionary history, discussing wolf-dog differences in the socialization period, fear response, sociability, and attachment to elucidate the effect of domestication. Secondly, we address its ontogeny, highlighting the importance of early life experiences, examining findings on different dog populations to discern the effect of adult life experiences, and reporting changes across the lifespan. Thirdly, we analyse the adaptive value of the dog-human relationship, considering the effects of human association on different dog populations. Fourthly, we elaborate on the mechanisms involved in the dog-human relationship, discussing underlying cognitive and genetic processes and findings on the neurophysiological effects of interacting with humans. Finally, we identify issues and remaining questions that deserve more scrutiny and suggest innovative approaches that could be explored to improve our understanding of dogs' human-directed sociability.