REINFORCEMENT MODALITY INFLUENCES PERFORMANCE IN A QUANTITY DISCRIMINATION TASK IN THE DOG

Quantity discrimination has been assessed in a variety of species and with a variety of paradigms. This preliminary study aimed to investigate whether the way dogs (Canis familiaris) were reinforced influenced their performance in a quantity discrimination task. The dog was kept on a lead, while an experimenter, wearing dark sunglasses, put two dishes (containing 1 and 8 food pieces) on the floor one meter in front of it, 60 cm apart. Olfactory cues were controlled for. The experimenter retreated, and the dog was freed after it had looked at both dishes. Choice of a dish was scored the very first time the nose of the dog approached it at 10 cm. Three sessions of six trials each were performed. In the differential reinforcement treatment ( 15 dogs) the dogs could eat the content of the chosen dish. In the non-differential reinforcement treatment ( 10 dogs), access to dish content was prevented and the owner gave the dog a standard treat after each choice. Three dogs of the non-differential treatment and 11 of the differential one reached binomial criterion for choosing the larger quantity significantly more often. Dogs from both groups chose above chance level in the first session of trials (and even in their very first spontaneous choice), but only those of the differential treatment were successful also in the second and third sessions. Data suggest that dogs have the cognitive ability to differentiate among quantities, but reinforcement modality can heavily affect their performance.