A revolution in our understanding of dog cognition has occurred in the past decade, with previous work by the Hare research group linking individual differences in cognition to working dog performance in adults. However, there has yet to be a large-scale longitudinal study tracking the course of cognitive development in any breed of puppies, and limited understanding of how different rearing strategies influence the development of canine cognition. This study will characterize the development of the cognitive traits that this team’s previous work has shown predicts a dog’s ability to succeed in assistance dog training. Working with the Canine Companions for Independence (CCI), cognitive traits will be characterized using a longitudinal design during the critical period of brain development from 8-20 weeks of age. Next, to test for the influence of different but common service dog rearing strategies on these skills, the investigators will test individual CCI puppies reared in human homes or together with same age peers on a college campus. In studying the cognitive abilities of service dogs, a better understanding of what psychological mechanism(s) successful service dogs rely on or are constrained by when helping humans will be detailed. This information can be used to better predict which puppies will be successful service dogs – improving the success of training while increasing the potential number of service dogs available. These findings will also provide the first set of baseline data on normal cognitive development in dogs as it relates to success in training programs and socialization strategies.