Abstract
Family dogs’ human-analogue attachment to the owner has long been recognised; however, how this dog–owner attachment develops and changes with age remains an open question. We examined age-related variation and the effect of training experience on the attachment behaviour in family dogs ( N = 222) using the Strange Situation Test (SST). Across three age groups (puppy–juvenile, adult, and senior dogs), dogs were assessed by scores for three behavioural factors: attachment to the owner, anxiety in the strange situation, and acceptance of a friendly stranger. Based on three basic behaviours, young puppies under 6 months of age already showed attachment behaviour towards their owners. In puppies–juveniles (2.8–12 months), age was not associated with any of the three factors. In adult dogs (1–7 years), age was positively associated with acceptance scores. In senior dogs (≥ 7 years), attachment scores increased with higher age. Training experience influenced behaviour in adulthood: dogs with greater training experience received lower attachment, higher acceptance, and lower anxiety scores. Further analyses revealed that the association between training and lower attachment was mediated by lower anxiety, likely indicating underactivation of the attachment system in the SST in highly trained dogs. Our findings show that the attachment between dogs and owners develops early, remains fairly consistent through adulthood, and becomes more pronounced in later life as dogs become increasingly dependent on human care. This pattern parallels the increased reliance on attachment figures observed in older humans and highlights family dogs as a unique model for investigating how ageing influences attachment.