Cross-sectional study of object permanence in domestic puppies (Canis familiaris).

Visual accommodation and object permanence tests were administered to 70 puppies (Canis familiaris), aged 4 weeks to 9 months. The results showed that understanding of visible displacement problems emerged at the 5th weeks and developed rapidly until the 8th week. Although the search behaviors of older puppies were more flexible, no further significant development was observed between 8 weeks and 9 months. The results on invisible displacement tests suggest that understanding of invisible displacement problems appears around the 1st year in dogs' development.