Dogs extend verbal labels for functional classification of objects

The relationship between language and human thought is an ongoing debate,¹ and it has been proposed that language shapes object categorization.² Words play an instrumental role in early perceptual categorization,^3,4 but the capacity to preferentially utilize object function over perceptual similarity in guiding the extension of novel words emerges later, in toddlers and preschoolers.^5,6,7,8 It is debated whether non-humans' ability to categorize objects is limited to perceptual features.^9,10 Only a few studies have investigated the extension of labels to categories, and these relied on a small number of extensively trained individuals who acquired a basic use of labels.^11,12,13,14 However, this differs markedly from how human infants naturally acquire language and adopt words as category markers.^15,16 We capitalized on the discovery of dogs with an outstanding ability to form a vocabulary of object verbal labels during spontaneous, natural interactions with their owners^17,18,19,20 to reveal that they generalize these labels to items that share only functional properties without sharing perceptual similarities. During naturalistic-like playful interactions, the dogs classified novel objects based on functional object use rather than mere shared perceptual attributes. This reveals functional classification beyond perceptual features connected to verbal label learning in a non-linguistic species in naturalistic setups. Such functional label generalization was only documented in a few individual animals after extensive formal training. The results provide insights into the diverse evolution of basic language-related skills²¹ and their relationship with other cognitive abilities. VIDEO ABSTRACT.